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Systematics, Paleobiology and Paleoecology of Late Miocene Sharks (Elasmobranchii, Selachii) from Panama

Permanent Link: http://ufdc.ufl.edu/UFE0041399/00001

Material Information

Title: Systematics, Paleobiology and Paleoecology of Late Miocene Sharks (Elasmobranchii, Selachii) from Panama Integration of Research and Education
Physical Description: 1 online resource (131 p.)
Language: english
Creator: Pimiento, Catalina
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2010

Subjects

Subjects / Keywords: isthmus, megalodon, neogene, nursery, shark, website
Zoology -- Dissertations, Academic -- UF
Genre: Zoology thesis, M.S.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: The late Miocene Gatun Formation of northern Panama contains a highly diverse and well sampled neritic fossil assemblage that was located in the Central American Seaway that connected the Pacific and Atlantic (Caribbean) oceans ~10 million years ago. The Gatun Formation likewise contains a relatively diverse selachian assemblage. Based on field discoveries and analysis of existing collections, the sharks from this unit consist of at least 16 taxa, including four species that are extinct today. The remaining portion indicates relatively long-lived species. Based on the known habitat preferences for modern selachian, the Gatun sharks were primarily adapted to shallow waters within the neritic zone. Also, in comparison with modern species, the Gatun shark fauna has mixed Pacific-Atlantic biogeographic affinities. Comparisons of Gatun dental measurements with other formations suggest that many of the species have an abundance of small individuals. One of this small-size species is the extinct Carcharocles megalodon, paradoxically the biggest shark that ever lived. Here, the tooth sizes from the Gatun Formation were compared with isolated specimens and tooth sets from different aged, but analogous localities. In addition, the total lengths of the individuals were calculated. This comparisons and estimates suggest that the small size of Gatun's C. megalodon is not related to timing (chronoclines), or to the tooth position within a variant jaw, and that the individuals from Gatun were mostly juveniles and neonates. I therefore propose the Miocene Gatun Formation as the first documented paleo-nursery area for C. megalodon from the Neotropics. It hence shows that sharks have used nursery areas for millions of years as an adaptive strategy during their life histories. For this research, approximately 400 fossil shark teeth were collected. This large collection has the great potential to be used not only for scientific research, but also as a teaching tool for young learners. One important goal of this non-traditional thesis is to convey scientific knowledge to the general public, and therefore a broader impact deliverable was produced: A kid-friendly and bilingual website about fossil sharks from Panama (http://stri.org/english/kids/sharks/), to engage young learners to science. The site was designed to create a quality online experience based on evaluations to different-aged young learners and following the best practices.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Catalina Pimiento.
Thesis: Thesis (M.S.)--University of Florida, 2010.
Local: Adviser: Macfadden, Bruce J.
Local: Co-adviser: Jones, Douglas S.

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2010
System ID: UFE0041399:00001

Permanent Link: http://ufdc.ufl.edu/UFE0041399/00001

Material Information

Title: Systematics, Paleobiology and Paleoecology of Late Miocene Sharks (Elasmobranchii, Selachii) from Panama Integration of Research and Education
Physical Description: 1 online resource (131 p.)
Language: english
Creator: Pimiento, Catalina
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2010

Subjects

Subjects / Keywords: isthmus, megalodon, neogene, nursery, shark, website
Zoology -- Dissertations, Academic -- UF
Genre: Zoology thesis, M.S.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: The late Miocene Gatun Formation of northern Panama contains a highly diverse and well sampled neritic fossil assemblage that was located in the Central American Seaway that connected the Pacific and Atlantic (Caribbean) oceans ~10 million years ago. The Gatun Formation likewise contains a relatively diverse selachian assemblage. Based on field discoveries and analysis of existing collections, the sharks from this unit consist of at least 16 taxa, including four species that are extinct today. The remaining portion indicates relatively long-lived species. Based on the known habitat preferences for modern selachian, the Gatun sharks were primarily adapted to shallow waters within the neritic zone. Also, in comparison with modern species, the Gatun shark fauna has mixed Pacific-Atlantic biogeographic affinities. Comparisons of Gatun dental measurements with other formations suggest that many of the species have an abundance of small individuals. One of this small-size species is the extinct Carcharocles megalodon, paradoxically the biggest shark that ever lived. Here, the tooth sizes from the Gatun Formation were compared with isolated specimens and tooth sets from different aged, but analogous localities. In addition, the total lengths of the individuals were calculated. This comparisons and estimates suggest that the small size of Gatun's C. megalodon is not related to timing (chronoclines), or to the tooth position within a variant jaw, and that the individuals from Gatun were mostly juveniles and neonates. I therefore propose the Miocene Gatun Formation as the first documented paleo-nursery area for C. megalodon from the Neotropics. It hence shows that sharks have used nursery areas for millions of years as an adaptive strategy during their life histories. For this research, approximately 400 fossil shark teeth were collected. This large collection has the great potential to be used not only for scientific research, but also as a teaching tool for young learners. One important goal of this non-traditional thesis is to convey scientific knowledge to the general public, and therefore a broader impact deliverable was produced: A kid-friendly and bilingual website about fossil sharks from Panama (http://stri.org/english/kids/sharks/), to engage young learners to science. The site was designed to create a quality online experience based on evaluations to different-aged young learners and following the best practices.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Catalina Pimiento.
Thesis: Thesis (M.S.)--University of Florida, 2010.
Local: Adviser: Macfadden, Bruce J.
Local: Co-adviser: Jones, Douglas S.

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2010
System ID: UFE0041399:00001


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1 SYSTEMATICS, PALEOBIOLOGY, AND PALEOECOLOGY OF LATE MIOCENE SHARKS (ELASMOBRANCHII, SELACHII) FROM PANAMA: INTEGRATION OF RESEARCH AND EDUCATION By CATALINA PIMIENTO A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLOR IDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2010

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2 2010 Catalina Pimiento

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3 To my husband

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4 ACKNOWLEDGMENTS This project was funded by NSF EA R 0418042, Sigm a Xi G2009100426, the Mitchell Hope Scholarship, and the Ken Er icson Scholarship. I want to specially give thanks to my advisor, Dr. Bruce MacFadden for his mentoring, support, encouragement and sympathy. He became a father during my masters degree and I have to thank God for giving me the best advisor I could have asked for. I will always a ppreciate his patience when I was too intense with the research, his comprehension when I was homes ick and just wanted to go see my family, and his sense of humor, especially during cold bori ng mornings. Also, I would like to thank Dr. Doug Jones, my co-advisor for being such a supportive and inspiring guide and for helping me to get out of trouble. Thanks to the remaining member s of my committee Dr. Jonathan Bloch and Dr. Rose Pringle for their helpful feedb ack and advise during this project. Dana Ehret has been a great colleague; I thank his interest in my re search and for being such a cooperative friend. A great share of this work was completed thanks to him. Thanks to everybody at the FLMNH for their constant help, and to Dr. Colette St. Mary for being very supportive and because I always could r each her, even with silly questions. Thanks Dr. Gordon Hubbell for helping with the identification of the material, for allowing me to study his private collecti on and for his helpful comments during this research. Special thanks to the Smithsonian Tropical Research Institute, specially to Carlos Jaramillo and his field team: Aldo Rincon, James Wilson, Cesar Silva and Sandra Suarez for their support during the fieldwork and for facilitating the materials collected. Thanks to the Direccion de Recursos Minerales of Panama for collecting permits, to Felix Rodriguez and Aaron O'Dea for facilitating previous collected material and to Luz Ovie do, Marisol Lopez and Ricardo Chong for helping with the website.

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5 Thanks to Rony Leder for helping with the id entification of the material; Dale Winkler from the SMU, and Dave Bohaska and R. Purdy from the NMNH for access to collections. Thanks to Gary Morgan for benefici al suggestions to this research. Thanks to Maria Ines Barreto for showing me the north when I was lost; to all my dear friends in Gainesville for making my life sweeter to my mom and dad for believing in me even when I doubted myself, to my brothers for bei ng my inspiration and to my husband: thank you my love for supporting me during these two years of abandonment, for making this tough journey enjoyable, for help in editing manuscripts, practicing ta lks, and for being a constant source of ideas.

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6 TABLE OF CONTENTS page ACKNOWLEDGMENTS...............................................................................................................4LIST OF TABLES................................................................................................................. ..........9LIST OF FIGURES.......................................................................................................................10LIST OF ABBREVIATIONS........................................................................................................ 12ABSTRACT...................................................................................................................................13CHAPTER 1 GENERAL INTRODUCTION.............................................................................................. 15Scientific Component........................................................................................................... ..15Broader Impact Component.................................................................................................... 172 LATE MIOCENE SHARKS (CHONDRICHTHYES, ELASMOBRANCHII, SELACHII) FROM THE GATUN FORMATI ON, PANAMA............................................. 20Introduction................................................................................................................... ..........20Geological, Paleontological, a nd Paleoecological Context.................................................... 21Methodology...........................................................................................................................24Materials..........................................................................................................................24Sampling Strategy...........................................................................................................26Systematic Paleontology........................................................................................................ .27Discussion...............................................................................................................................48Taxonomic Longevity..................................................................................................... 52Size..................................................................................................................................52Habitat Preferences.......................................................................................................... 533 ANCIENT NURSERY AREA FOR THE EXTINCT GIANT SHARK MEGALODON ( CARCHAROCLES MEGALODON ) IN THE MIOCENE OF PANAMA............................. 65Introduction................................................................................................................... ..........65Materials and Methods...........................................................................................................69Temporal Comparisons of Similar Faunas...................................................................... 70Life Stage Comparisons.................................................................................................. 70Total Length Estimates.................................................................................................... 71Results and Discussion......................................................................................................... ..71Temporal Comparisons of Similar Faunas...................................................................... 71Life Stage Comparisons.................................................................................................. 72Total Length Estimations................................................................................................ 73Concluding Remarks: Nurs ery Area Hypothesis............................................................ 74

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7 4 BROADER IMPACT COMPONENT: ENGAGING YOUNG LEARNERS IN SCIENCE T HROUGH A WEBSITE ON FO SSIL SHARKS FROM PANAMA................ 78Introduction................................................................................................................... ..........78Problem............................................................................................................................79Objective..........................................................................................................................79Background......................................................................................................................80Fossil Sharks from Panama as a Science-Engaging Tool....................................................... 83Why Fossil Sharks?.........................................................................................................83Why Panama?..................................................................................................................83Front-End Evaluation: Learning fr om and about the Audience............................................. 85Website Design.......................................................................................................................87Formative Evaluation...................................................................................................... 87Web 2.0............................................................................................................................88Website Sections............................................................................................................. 89Geologic time...........................................................................................................89Fossil sharks.............................................................................................................90Megalodon................................................................................................................90Present and future..................................................................................................... 90Recommendations and Best Practices.................................................................................... 91Communication with the Team....................................................................................... 91Keep it Simple................................................................................................................. 91Short Texts.................................................................................................................... ...92Evaluations Mean Everything......................................................................................... 92The Future of the Website...................................................................................................... 925 GENERAL CONCLUSIONS............................................................................................... 100APPENDIX A CHAPTER 2 TOOTH DIAGNOSTIC CHARACTERS AND DIMENSIONS .................. 104B CHAPTER 2 DATA............................................................................................................. 105C CHAPTER 3 REPRESENTATION OF A CARCHAROCLES MEGALODON DENTITION.........................................................................................................................107D CHAPTER 3 CARCHAROCLES M EGALODON COLLECTION FROM THE GATUN FORMATION...................................................................................................................... .108E CHAPTER 3 LINE REGRESSIONS FOR TOOTH MEASUREMENTS. ......................... 109F CHAPTER 3 MEASUREMENTS FROM BONE VALLEY FORMATI ON..................... 110G CHAPTER 3 MEASUREMENTS FROM THE CALVERT FORMATI ON...................... 112H CHAPTER 3 MEASUREMENTS J UVENILE TOOTH SET............................................. 114

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8 I CHAPTER 3 MEASUREMENTS ADULT TOOTH SET..................................................115J CHAPTER 3 TOTAL LENGTH.......................................................................................... 116K CHAPTER 4 FOCUS GROUP SURVEY............................................................................117Objectives.............................................................................................................................117Assent ScriptParent or Guardian of Minor....................................................................... 117Procedure..............................................................................................................................117LIST OF REFERENCES.............................................................................................................119BIOGRAPHICAL SKETCH.......................................................................................................131

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9 LIST OF TABLES Table page 2-1 Number of specimens when two differ ent collection m ethods employed in relation with teeth CH.....................................................................................................................632-2 Paleoecology and inferred habitats of the elasmobranch fauna from the Gatun Formation; late Miocene of Panama..................................................................................643-1 Carcharocles megalodon isolated teeth from the Gatun Formation, Panama................... 77

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10 LIST OF FIGURES Figure page 1-1 Area of study......................................................................................................................19 2-1 Graph showing the num ber of teeth colle cted in the Gatun Formation using 2 different techniques............................................................................................................55 2-2 Ginglymostoma delfortr iei .................................................................................................56 2-3 Carcharocles megalodon. ..................................................................................................56 2-4 Hemipristis serra ..............................................................................................................57 2-5 Galeocerdo cuvier ..............................................................................................................57 2-6 Physogaleus contortus .......................................................................................................57 2-7 Carcharhinus sp. ................................................................................................................58 2-8 Carcharhin us falciformis ...................................................................................................58 2-9 Carcharhinus leucas from the late Miocene Gatun Form ation, Panama, UF 241829, upper tooth.........................................................................................................................59 2-10 Carcharhinus obscurus ......................................................................................................59 2-11 Carcharhin us perezi ...........................................................................................................59 2-12 Carcharhinus plumbeus .....................................................................................................60 2-13 Negaprion brevirostris .......................................................................................................60 2-14 Rhizoprionodon sp.. ...........................................................................................................60 2-15 Sphyrna sp.. ........................................................................................................................61 2-16 Sphyrna lew ini ...................................................................................................................61 2-17 Sphyrna mokarran .............................................................................................................61 2-18 Estimated paleodepth of the Gatun Forma tion based on depth preferences of extant and related shark species .................................................................................................... 62 3-1 Temporal comparisons of similar faunas........................................................................... 75 3-2 Life stage com parisons...................................................................................................... 75

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11 3-3 Total length histogram ....................................................................................................... 76 4-1 Young learners find collecting fossil sharks a fascinating subject.. .................................. 94 4-2 A-C. Young learn ers from the Isaac Rabi n School answered a survey after they observed a fossil shark tooth.............................................................................................. 95 4-3 Form ative evaluation......................................................................................................... 96 4-4 Geologic Time.............................................................................................................. .....96 4-5 Fossils.................................................................................................................... ............97 4-6 Megalodon.................................................................................................................. .......98 4-7 Sharks Present and Future.................................................................................................. 99

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12 LIST OF ABBREVIATIONS CTPA Center of Tropical Pa leobiology and Archaeology CH Crown Height FLMNH Florida Museum of Natural History NMNH National Museum of Natural History UF University of Florida, Gainesville, Florida SMU Shuler Museum of Paleontology, Southern Methodist University, Dallas, Texas. STRI Smithsonian Tropical Research In stitute, Panama, Republic of Panama TL Total Length W Crown Width

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13 Abstract of Thesis Presen ted to the Graduate School of The University Of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science SYSTEMATICS, PALEOBIOLOGY, AND PALEOECOLOGY OF LATE MIOCENE SHARKS (ELASMOBRANCHII, SELACHII) FROM PANAMA: INTEGRATION OF RESEARCH AND EDUCATION By Catalina Pimiento May 2010 Chair: Bruce MacFadden Cochair: Douglas Jones Major: Zoology The late Miocene Gatun Formation of norther n Panama contains a highly diverse and well sampled neritic fossil assemblage that was located in the Central American Seaway that connected the Pacific and Atlantic (Cari bbean) oceans ~10 million years ago. The Gatun Formation likewise contains a relatively di verse selachian assemblage. Based on field discoveries and analysis of exis ting collections, the sharks from this unit consist of at least 16 taxa, including four species that are extinct t oday. The remaining porti on indicates relatively long-lived species. Based on the known habitat preferences for modern selachian, the Gatun sharks were primarily adapted to shallow waters within the neritic zone. Also, in comparison with modern species, the Gatun shark fauna has mi xed Pacific-Atlantic biogeographic affinities. Comparisons of Gatun dental measurements with other formations suggest that many of the species have an abundance of small individuals. One of this small-size species is the extinct Carcharocles megalodon, paradoxically the biggest shark that ever lived. Here, the tooth sizes from the Gatun Formation were compared with is olated specimens and tooth sets from different aged, but analogous localities. In addition, the total lengths of the individuals were calculated. This comparisons and estimates suggest that the small size of Gatun's C. megalodon is not

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14 related to timing (chronoclines), or to the tooth position within a variant jaw, and that the individuals from Gatun were mostly juveniles and neonates I therefore propose the Miocene Gatun Formation as the first doc umented paleo-nursery area for C. megalodon from the Neotropics. It hence shows that sharks have used nursery areas for millions of years as an adaptive strategy during their life histories. For this research, approximately 400 fossil shar k teeth were collected. This large collection has the great potential to be used not only for scientific research, but also as a teaching tool for young learners. One important goal of this non-tr aditional thesis is to convey scientific knowledge to the general public, and therefore a broader impact deliverable was produced: A kid-friendly and bilingual website about fossil sharks from Panama ( http://stri.org/e nglish/kids/sharks/ ), to engage young learners to science. The site was designed to create a quality online experience based on evaluations to different -aged young learners and following the best practices.

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15 CHAPTER 1 GENERAL INTRODUCTION Sharks are included in the cla ss Chondrichthyes, a very ancien t clad e that dates from at least ~400 Million years ago during the Paleozoi c Era (Hubbell 1996). Sharks are very important apex predators in modern oceans and they include some of the most ancient vertebrates still around today (Cione et al. 2007). In the geologic record, shark teeth are the most abundant vertebrate fossils present wo rldwide (Hubbell 1996). The presen ce of fossil shark teeth in different localities around the wo rld allows determination of th e composition of ancient marine faunas. Numerous fossil shark species have been found at different Miocene localities worldwide. These discoveries are essential to understand th e ecology of the fauna during that particular period of time. During the Pliocene about 4 m illion years ago, the Panamanian Isthmus was formed by the closing of an oceanic gateway that had been open since the Mesozoic (Cronin and Dowsett 1996). Before this closure, marine warm shallow waters (Teranes et al., 1996) covered southern Central America forming the Central America Seaway. In this non-traditional thesis, fossil sharks are the main subject of study. This work is divided in two main components; th e first is the scientific compone nt and the second is a broader impact deliverable Scientific Component Woodring (1957, 1959, 1964) described the inverteb rates of the Tertiary Caribbean F auna Province. Within this Caribbean Province, differe nt fossil shark teeth have been recorded in a few publications. These findings reveal the composition of the Caribbean Miocene shark faunas from Panama (Blake 1862, Gillette 1984, Pimien to et al. 2010), Venezuela (Aguilera, and Rodrguez de Aguilera, 2002, 2004) and Ecuador ( Longbottom, 1979).

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16 Related to these occurrences, in order to furthe r elucidate the fossil r ecord of sharks form Panama, particularly from the Gatun Formation, all relevant fossil shark tooth material known were reviewed and re-described in this resear ch. Additionally, new specime ns were collected and identified to add to the record. The additional ne w specimens were also compared to the original material collected and described (G illette 1984). In this research, a better census of the ancient selachian biodiversity during th e late Miocene of Panama was completed, expanding our knowledge of ichthyofauna of the Gatun Formation. This work is described in Chapter 2 and is currently under revision to be published on our very own Bulletin of the FLMNH. Based on the work mentioned above and other studies on different ar eas, the Gatun is a highly fossiliferous Neogene formation located in the Isthmus of Panama (Figure 1-1) with a diverse fauna of sharks. It was located within the marine Sea Way (Central America Sea Way) that connected the Pacific Ocean and the Caribbean Sea during the late Miocene (~10Ma) [8]. Studies of different taxa indicate that it was a shallow-water ecosystem (~ 25 m depth) with higher salinity, mean annual temperature variati ons, seasonality and productivity relative to modern systems in this region. From the shark species found in the Gatun Formation, Megalodon (Carcharocles megalodon) has generated curiosity in both the scient ific community and among fossil collectors. The reason for this is because this extinct lamnoi d shark is the biggest pr edator that ever lived, exceeding estimated body sizes attributed to even the largest carnivorous dinosaur. A single C. megalodon tooth can reach 168 mm in height, and studi es have estimated that an adult could reach more than 15 m of total length (Gottfried et al. 1996). Even when sharks are apex predators in th e oceans, juveniles are preyed by larger individuals during the first years (Heithaus 2007). In order to prot ect their offspring, females lay

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17 their eggs, or give birth in sh allow and productive zones called nursery areas for juveniles to use these environments as a refuge from larger pr edators (Heupel et al. 2007). In this research, I hypothesize that of Panama was used as a pale o-nursery area during the late Miocene for the juveniles of C. megalodon. Nursery areas for C. megalodon have been proposed based on anecdotal records in a few previous publications. In this study, C megalodon teeth were collected and measured from the Gatun Formation of Panama. Surprisingly, large teeth are uncommon with specimens recovered having crown heights ranging betwee n 16 to 72 mm, far smaller than the range of variation seen in collections of C. megalodon that span an expected size range to include juveniles and adults. In this research, tooth sizes from the Gatun were compared with specimens from different, but analogous localities. Additionally, from these meas urements the total lengths of the individuals from the Gatun were calculated. The results obtained allowed to determine the age class/size of individuals that inhabited the sh allow-water habitats of the late Miocene Gatun Formation, ~10 million years ago, and to support the hypothesis that Panama was used as a nursery area for young C. megalodon during the late Miocene. This work is described in Chapter 3 and will be soon submitted to the PLos Biology Journal. In addition, it was presented to the Society of Vertebrate Paleontology 69th Annual meeting, where it recei ved media attention from the Discovery Channel [ http://news.discovery.com/anima ls/m egalodon-nursery-prehistoricsharks.html ]. Broader Impact Component After investigating ancient sharks of th e Neotropics, one m ay wonder why it is so important to create knowledge and do science? Science is a powerf ul enterprise that can improve the lives of human beings in fundamental ways. It requires not only th e work of scientists,

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18 engineers and doctors, but also journalists, teacher s, politicians, and every one that can contribute to the great enterprise of science (Michaels et al. 2008). The development of science for young learners allows them, among other things, to think critically, giving them power to become memb ers of society rather than mere observers (Michaels et al. 2008). Evaluations in museums have revealed that fossil sharks are very attractive for young learners (MacFadden, 2006). Fossil shark teeth permit the understanding of the composition of ancient faunas as well as the environmental conditions that allows us to comprehend the climate changes that have occurred in earths history. Ther efore, the history of fossil sharks in Panama facilita tes understanding several important concepts of natural sciences such as biology, ecology, geology and paleontology. This topic sparks young learners curiosity and in turn leads to the ac quisition of science knowledge. The Internet offers a new way to teach science, particularly with th e interactivity of Web 2.0 technology. Contrary to the st atic textbooks, with the Internet scientific concepts can be communicated in a dynamic and creative way, which is closer to how science really works. This turns out to be more attractive and less intimi dating for both students and teachers and does not ignore fun (Sanders 2009). For this Masters research, and in collaborati on with STRI and the FLMNH, approximately 400 new fossil shark teeth specimens from the Miocene Gatun Formation of Panama, were collected. This large collection ha s a great potential to be used not only for scientific proposes, but also as a teaching tool for young learners. Th e objective of the broader impact component of this research is to develop of a kid-friendl y and bilingual website about fossil sharks from Panama to engage young learners to science. This website, hosted by the STRI kids webpage [ http://www.stri.org/kids ], is described in Chapter 4. It will be a novel m odel for education using

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19 the Internet as a tool, and will promote science and technology to society, particularly for the next generation. Figure 1-1. Area of study. A. Location of Gatun Formation (shaded box) in northern Panama. B. Expanded geological map (from See Belo w shaded box in Figure A) showing exposures of the Gatun Formation and surr ounding rock units (modified from Coates et al., 1992). B. The four fossil localities collected from the Gatun Formation during this study include: (1) Las Lomas, (2) Isla Payardi, (3) Cuatro Altos, and (4) Banco EE.

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20 CHAPTER 2 LATE MIOCENE SHARKS (CHONDRICHT HYES, ELASMOBRANCHII, SELACHII) FROM THE GATUN FORMATION, PANAMA Introduction Shark teeth are the most commonly collected vertebrate fossils found in shallow-water marine sediments worldwide. Of relevance to this report, despite their abundance in space and time, Neogene sharks are poorly known in the literature from the circumtropical oceans of the Neotropics (American tropics). Th e late Miocene Gatun Formation consists of a series of highly fossiliferous exposures that outcrop in the Isth mus of Panama with a highly diverse fauna, including macroand micro-invertebrate s (Woodring 1957, 1959, 1964; Borne et al. 1996; Collins 1996; Jackson et al. 1996; Hecht, work in pr ogress). Previous studies of different taxa of the Gatun Formation indicate that during the late Miocene, this area was a shallow-water seaway (the Central America Seaway) th at supported a neritic environm ent and connected the Pacific Ocean and the Caribbean Sea (Teranes et al. 1996) Therefore, the Gatun marine faunas existed during a time of active transoceanic interchange and dispersal before the time of the full closure of the Isthmus about 3.5 to 4 million years a go (Coates & Obando 1996; Gussione et al. 2004; Huag et al. 2001). This closure was a key vicari ance event for tropical biot ic evolution (Cronin & Dowsett 1996) that resulted in increased of habitat and biogegraphic complexity (Jackson & Budd 1996). Blake (1862) reported three fo ssil shark species from the Miocene deposits at Panama in a very short publication. Since th at time, Gillette (1984) has p ublished the only other work on fossil sharks from Panama. Based on the scr eenwashing of sediments in 1978 and 1979 at the Sabanitas (=Las Lomas in this study) locality in the Gatun Formation, he described the marine ichthyofauna, which included 11 shark taxa. In order to further elucidate the shark fossil record

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21 of the Gatun Formation, I reviewed and re-descr ibed all relevant fossil shark tooth material known. Additionally, we collected and have identi fied 247 new specimens to add to the record. The additional new specimens, which we collected between 2007 to 2009 by surface prospecting, were also compared to the original material collected and described (Gillette 1984) from the Gatun Formation. In doing so we sampled the different tooth size classes that regularly result when using these two different field tech niques. Therefore a bette r census of the ancient selachian biodiversity during th e late Miocene of Panama was completed, expanding our knowledge of ichthyofauna of the Gatun Formation. Over the past 20 years, the Gatun Formati on localities have been extensively used to extract sediment for construction. During the pa st 5 years, these extraction activities have increased substantially. Based on observations ma de while surface prospecting, I predict that these outcrops will soon likely be excavated comp letely. The objective of this work is to reconstruct the Gatun Formation shark fauna ba sed on the study of the new fossil material collected, the fossil material from previous work and the information available on extant related species. Using this information I will then eval uate the, ecology, taxonomic longevity, sizes and habitat preferences of the Gatun sharks to bett er understand the marine faunas of the ancient Neotropics prior to the formation of the Isthmus of Panama during the Pliocene. Geological, Paleontological, and Paleoecological Context The fossil shark teeth described in this Ch apter were collected from Neogene marine sediments of the Gatun Formation. This formati on crops out in a broad area of north-central Panama (Figure 1-1) extending along the northern shore of Lake Gatun ca. 15 km northward to the Caribbean Sea, and east and west of Colon, w ithin the Panama Canal structural basin. In the current study area, the gently dipping (i.e., 5 to 10o) Gatun Formation, overlies either unnamed

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22 Cretaceous volcanics or the upper Oligocene sedi ments and volcanics of the Caimito Formation depending upon the specific location (Woodring 1957; Coates et al. 1992; Coates 1996a). The Gatun Formation, with a composite out crop and subsurface thickness of 500 m, consists of three described members. Of relevance to this research, most of the fossils collected during our study, and likely those of Gillettes (1 984) from Sabanitas (= Las Lomas, also see detailed locality information below), occur within the lower member of the stratotype (section 1, Sabanita-Payardi) and referred sections (Coates 1996a, Text-f ig. 4; 1996b). The lithology of these sections characteristically consists of ma ssive, gray-green clayey siltstone and interbedded, more indurated concretions. This part of the Gatun Formation is highly fossiliferous, with diverse molluscan (up to 259 genera and 359 spec ies listed for the middle Gatun, Jackson et al., 1996) assemblages that are classically descri bed in the literature (e.g., Woodring 1957, 1959 & 1964). At some localities within the Gatun Form ation (e.g., Las Lomas located ~12 km southeast of Colon in Figure 1-1 the highly fossiliferous nature of the se diments exposed along weathered bedding planes results in pavements of macrofossils, i.e., primarily consisting of bivalves and gastropods. Within this taphonomic context, ve rtebrate macrofossils recovered by surface prospecting consist mostly of shark teeth and ray tooth plates, although osteichthyan (e.g., barracuda Sphyraena) teeth and turtle fragments are also common. In addition, screenwashing of the clastic sedimentary matrix yields rich microfossil assemblages, including ostracods (Borne et al. 1996; Hecht, work in progr ess), benthic foraminifera (C ollins 1996), bony fish otoliths (Aguilera & De Aguilera 1996), and many of the smaller shark taxa reported by Gillette (1984). Multiple lines of biostratigraphic evidence from the rich marine invertebrate fauna indicate that the Gatun Formation is late Miocene in age, with a total range represented by the composite stratigraphic section spanning from about 12 until 8.4 million years ago (Coates 1996a). In terms

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23 of comparisons with other similarly diverse and relatively well-s ampled marine faunas in the coastal regions in the western hemisphere, several faunas bracket those of the Gatun Formation: (a) Older, early-middle Miocene assemblages c ontaining sharks include the Pungo River (Ward & Bohaska 2008), Agricola Fauna, Florida (Morgan 1994), Calvert Fauna, Maryland (Tedford et al. 2004); Domo de Zaza, Cuba (MacPhee & Itur ralde-Vinent 1994); the Cantaure Formation, Venezuela (Lxico Estratigrfico de Venezuel a 1997); the Grand Bay Formation of Carriacou, the Grenadines, Lesser Antilles (Donovan et al. 2003) and the Uscari Formation, Costa Rica (Pizarro 1986); (b) rough ly contemporaneous late Miocene as semblages include the Love Bone Bed Local Fauna (L.F.) and McGehee L.F., Florida (Hulbert 2001), St Marys Formation, Maryland, the Canmar Formation, Cuba (It urralde-Vinent, 1969) and the Rio Banano Formation, Costa Rica (Taylor 1975); and (3) yo unger, early Pliocene as semblages include the Yorktown, North Carolina (Ward & Bohaska 2008), Bone Valley, Florida (Morgan 1994; Tedford et al. 2004), upper Pisco, Peru (D e Muizon & DeVries 1985) and the Cubagua Formation, Venezuela (Lxico Estr atigrfico de Venezuela 1997). With regard to paleoecology and paleogeogra phy of the Gatun Formation, the foraminifera (Collins 1996), ostracodes (Borne et al. 1996), an d fish otoliths (Aguilera & De Aguilera 1996) all indicate a shallow-water marine shelf neri tic environment with a depth between 20 to 40 m (Teranes et al., 1996). Studies of oxygen isotope ratios preserved in mollusk shells from the Gatun Formation indicate that salinity, annual temperature vari ations, relative seasonality and productivity were more pronounced during the late Miocene relative to those of today (Teranes et al. 1996). The Gatun Formation and its faunas were located in a productive shallow marine seaway that connected a broad and unified fauna province during the late Miocene, ~10 million years ago. Thus, the Gatun marine faunas exis ted during a time of active transoceanic

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24 interchange and dispersal (Col lins et al. 1996; Newkirk & Ma rtin 2009) within the Central American Gateway (e.g., Gussione et al. 2004) or Central American Seaway (Newkirk & Martin 2009) before the time of the full closure of th e Isthmus about 3.5 to 4 million years ago (Coates & Obando 1996; Gussione et al. 2004; Huag et al. 2001). It is well documented in the literature that the closing of the Isthmus resulted in the Great American Interchange on land (Stelhi & Webb 1985), as well as biogeographi c separation (vicariance ev ent) of the once continuous marine distribution, resulting in the precursors of the modern-day Caribbean and Pacific marine faunal provinces. Methodology Materials Relevant specim ens from the UF and SMU vertebrate paleontology collections were examined during this study. The following codes ar e used in the text: UF locality YPA017, Las Lomas (9.66N, 79.34W); YPA020, Banco EE (9 59.11N, 79 5.36W); YPA021, Isla Payardi (9.18N, 79.50 W); YPA022, Cuatro Altos (9.08N, 79.80W). The UF material was collected by surface pr ospecting from the late Miocene Gatun Formation, Panama, between August 2007 and March 2009 from four different localities (Figure 1-1) by the Panama Canal Project Field Team of the Center of Tropical Paleobiology and Archaeology of STRI, as well as by UF scientis ts. In total, 247 isolated shark teeth were collected by UF-STRI Panama Cana l Project Field Team and are de signated with a UF catalogue number, with each number corresponding to one sp ecimen, which are also are available in our online data base [ http://www.flmnh.ufl.edu/databases/VP/intro.htm ]. The m aterial borrowed from the SMU Vertebra te Paleontology collection was recovered in 1978 and 1979 in an exposure that measured ~200 x 400 m from a single lo cality (equivalent to

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25 Las Lomas (YPA017)) also called Sabanitas This collection method consisted of screenwashing ~900 kg of sediment using traditi onal wet-sieving methods (for more detailed information see Gillette, 1984). A total of 157 is olated shark teeth were borrowed and studied from SMU, every tooth is designated with a SM U catalogue number, however several teeth have been designated to the same number, i.e., they were catalogued as lots. Given the fact that surface prospecting was done by the research team, and also that the SMU specimens that were collected by screenwashing (Gillette 1984) were studied, the different size classes that regularly result from these two different field techniques have been sampled and therefore better census ancient selachian biodiversity during th e late Miocene of Panama was constructed. Updated distribution and age range data for each extinct taxa were taken among other scientific references, from the Paleobiol ogy Database [www.paleodb.org], as listed in the Systematic Paleontology section below. Likewise distributional data fr om extant selachians were taken from Compagno, 1984 and FishBase [ http://www.fishbase.org ]. Thus, a total of 387 isolated teeth from both UF a nd SMU collections from the Gatun Formation were identified and studied. Specimens were first identified using comparative collections available at UF. Our identifications were then verified with the collaboration of Dr. Gordon Hubbell in his private collection in Gaines ville, Florida. Tooth terminology follows the work of Shimada (2002). Appendix A describes th e relevant diagnostic characters used to identify the material as well as the meas urement dimensions. Tooth measurements (in millimeters) can bee seen in Table 2-1. These measurements were compared with previous works on the Neogene sharks of the Pungo River Formation (middle Miocene) and the Yorktown Formation (early Pliocene) at Lee Creek Mine, North Carolina (Purdy et al., 2001), which are

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26 respectively younger and older th an Gatun. Common names were taken from Cocke (2002) for extinct species and Compagno (1984) for extant speci es so this study can also be useful for fossil collectors. Sampling Strategy Fossil shark teeth are oftentimes collected casually and as such do not represent a systematic sampling that is necessary to understand and reconstruct, to the best of our ability, the ancient taxonomic biodiversity repr esented in the fossil record. The goal of this study is to assess ancient selachian biodiversity as fully as possible. In doing so, a total of 387 isolat ed shark teeth were collected and identified from the late Miocene Gatun Formation in Panama. Of the 159 teeth recovered from Gillette's (1984) work (screenwashing, 1 locality), I identified 8 shark taxa. In addition, from the 230 teeth collected by our team (surface prospecting, 4 loca lities) I identified 13 shark taxa (Table 2-1) for a total of 16. Both methods proved useful in find certain taxa (Figure 2-1). Small teeth such as those from Rhizoprionodon sp. and Sphyrna lewini were only found when screen washing. Taxa with a broad tooth size range such as Sphyrna sp, Carcharhinus sp. and Negaprion brevirostris were found with both screenwashing and surface prospecting techniques. The remaining taxa (the largest teeth) were found only when surface prospecting. Comparisons with the SMU collections were im portant for the identification of 3 taxa. In contrast, by surface prospecting I was able to identify approximat ely 80% of the total selachian fauna. By combining these two methodologies, I am reducing the collecting bias. On the other hand, since shark teeth do not distribute uniform ly in the sediment (as opposed to rays) (O. Aguilera, Pers. Comm., 2009), I highly recommend surface prospecting rather than screenwashing when collecting shark teeth.

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27 Systematic Paleontology Class CHONDRICHTHYES Huxley 1880 Subclass EL ASMOBRANCHII Bonaparte 1838 Order ORECTOLOBIFORMES Applegate 1974 Family ORECTOLOBIDAE Jordan & Fowler 1903 Genus GINGLYMOSTOMA Mller & Henle 1838 GINGLYMOSTOMA DELFORTRIEI Daimeries 1889 Common name: Extinct nurse shark Referred specimens: Three isolated teeth; indeterminate position: SMU 76460 and SMU 76470. Described in Gillette (1984). Specific locality: YPA017. Distribution: Miocene, from Costa Rica and Florida; early Miocene of Venezuela and Guinea; and middle Miocene of France and Portug al, late Miocene of Panama (Cappetta 1987; Gillette 1984; Laurito 1999; Aguilera & De Aguilera 2001; Hulbert et al. 2001). Description: The only unbroken G. delfortriei tooth from the Gatun Formation measures 5.0 mm in CH and 8.4 mm in W (Figure 2-2). For a detailed description see Gillette, 1984. Discussion: The dentition of G. delfortriei is adapted for clutching, which is useful for feeding on fish, mollusks, corals, sea urchins and tunicates (Kent 1994). Ex tant species of the genus Ginglymostoma are reef associated, near-shore, bot tom dwelling sharks that inhabit temperate and tropical waters at a depth range of 0 130 m. They al so nurse in estuarine or nearshore shallow environments (McCandless et al. 2007). Order LAMNIFORMES Berg 1958 Family OTODONTIDAE Glckman 1964 Genus CARCHAROCLES Jordan & Hannibal 1923

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28 CARCHAROCLES MEGALODON Agassiz 1843 Procarcharodon megalodon megalodon (Gillette 1984:176) Carcharodon megalodon (Blake, 1862:316) Carcharodon megalodon (Aguilera & De Aguilera, 2004:370) Common name: Megalodon Referred specimens: 16 isolated teeth; upper anteriors: UF 237898, UF 237949, UF 237955 and UF 242804; lower anteriors: UF 237950 and UF 237959; upper laterals: UF 237914, UF 237951 237952 and UF 242802 242803; lower lateral: UF 237953; upper posterior: UF 237957; lower posterior: 237956; indeterminant position: UF 242801. Specific localities: YPA017 and YPA021. Distribution: Cosmopolitan, ranges from the Miocene to the Pliocene, including the Miocene of Japan, USA (Florida, Maryland, New Je rsey, California, Virginia, North and South Carolina), Madagascar, Australia (Victoria), India, Slovakia, Austria, Italy, Portugal (Lisbon Province), France (Aquitaine Region), South Afri ca (KwaZulu-Natal), Mexico (Baja California), Chile, Panama, Venezuela, Peru, Ecuador, Costa Rica, Cuba, Puerto Rico, The Grenadines and Jamaica. Pliocene of Australia (Victoria), USA (Florida and North Caro lina), and New Zealand (Hawera) (Blake 1862; Longbottom 1979; Gill ette 1984; De Muizon and DeVries 1985; Long 1993; Iturralde-Vinent 1996; Laurito 1999; Aguilera and De Aguilera 2001; Donovan and Gunter 2001; Hulbert et al. 2001; Nieves-Rivera 2003; Portel l et al. 2008; www.paleodb.org, 26 March 2009, using the name Carcharodon megalodon). Description: The diagno stic characters of C. megalodon teeth include large size, triangular shape, broad serrated crown, lingual face convex, labial face flat, large neck, robust, thick, angled or U-shaped root with disp ersed foramina. Juvenile teeth of C. megalodon can present

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29 cusplets (Ward & Bonavia 2001). C. megalodon differs from C. carcharias by lacking a labiolingually flattened crown (Purdy et al. 2001), havi ng larger roots and finer, more regular and lobed serrations (Nyberg et al. 2 006) and the presence of a neck. The C. megalodon teeth from the Gatun Formation range in size from 16.0 to 54.2 mm in CH and from 16.1 to 47.7 mm in W. Anterior teeth are symmetrical (Figure 23A and C), whereas the laterals are distally inclined (Figure 2-3B), UF 237914 also presents lateral cusplets indica ting a juvenile stage. Discussion: C. megalodon is the largest macropredatory shar k to have ever lived and is among the largest known fishes. Teeth from C. megalodon can reach 168 mm in CH and TL is estimated to have been over 15 m (Gottfried 199 6). The teeth from the early Pliocene Yorktown Formation at Lee Creek Mine range in size from 60.0 to 150.0 mm in CH (Purdy et al. 2001). C. megalodon has a wide occurrence in tropical to temperat e latitudes of the ancient oceans, with an apparent preference for coastal ha bitats (Gottfried el al.1996). Purdy (1996) proposed nursery areas for Carcharocles based on the abundance of juvenile teeth accompanied by primitive odontocete and sma ll mysticete skulls in Chandler Bridge Formation of South Carolina. Based on the extant white shark and fossil evidence, Purdy (1996) also inferred that they used warm-water ar eas for nurseries. The relatively small size of C. megalodon teeth from the Gatun Formation (Figure 23) compared with other localities is notable; Blake (1862) also noticed this in his publication and will be th e topic of another study (Pimiento et al., in progress). Order CARCHARHINIFORMES Compagno 1977 Family HEMIGALEIDAE Compagno 1984 Genus HEMIPRISTIS Agassiz 1843 HEMIPRISTIS SERRA Agassiz 1843

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30 Common name: Snaggletooth shark Referred specimens: 54 isolated teeth; uppers: UF 237919 237948, UF 241803 241808, UF 241835 and UF 242810 242817; lowers: UF 241801-241802, UF 242805 -242809 and SMU 76467. Specific localities: YPA017, YPA020 and YPA022. Distribution : Miocene to Pliocene. Miocene of USA (South Carolina, New Jersey, Virginia and Maryland), Italy, Germany, Fiji, Saudi Arabia, India, Pakistan, Madagascar, Australia, Java, Zaire, Japan, Venezuela, Cuba, Peru (Ica), Costa Rica, Panama, The Grenadines, Mexico (Baja California and Yucatan), Argentina (Entre Rios), Saudi Arabia, India, Pakistan, Madagascar, Australia, Java, Zaire and Japan. Pliocene of USA (Florida and North Carolina), Angola and Zanzibar (Cappetta 1987; Iturra lde-Vinent et al. 1996; Laurito 1999; Purdy et al. 2001; MacPhee et al. 2003; Aguilera & De Aguilera 2001, 2004; Portell et al. 2008; www.paleodb.org, 6 April 2009, using the name H. serra ). Description: Teeth of H. serra from the Gatun Formation demonstrate diagnostic characters of the species such as dignathic heterodonty (Figure 2-4). Upper Teeth: Crown curved distally, oblique coarse serrations, serrations do not continue to the apex, mesial cutting edge rectilinear at its base, distal cutting edge concave and with fewer serrations; root high and compressed with a lingu al protuberance forming a Z-shape. Teeth are generally broader than the correspo nding lowers (Figure 2-4A and B). Lower Teeth: Long pointed crown, lingually slanted or inclined, labial face convex, no serrations on the crown, small se rrations or cusplets near the ba se, bilobated root with a lingual protuberance (Figure 2-4C and D)

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31 Upper teeth of H. serra differ from Carcharhinus by having a distinctively smooth apex and oblique serrations; lower teeth differ from the genus Carcharias by having incomplete cutting edges on both mesial and distal side marg ins that are limited to approximately the apical third of the crown (Kent 1994). The dentition of H. serra differs from adult females of the extant species, H. elongatus, by having more straight crowns in their upper te eth (Purdy et al., 2001). This species is very common from the Gatun Formation selachian fauna and vary greatly in size, from 5.4 to 21.6 mm in CH and 5.2 to 29.0 mm in W (Figure 2-4). Discussion: The large size of H. serra teeth (up to 45.0 mm) sugge sts that this species reached total lengths much greater than the living H. elongatus, perhaps up to 6 m (Kent 1994). Based on its large upper teet h (presumably analogous to those of the tiger shark, Galeocerdo cuvier ), H. serra was able to catch large prey (Kent 1994). H. serra seems to increase in size through its evolutionary history (Purdy et al. 2001). Adult teeth of H. serra teeth from Pungo River Formation range between 14.1 and 29.1 mm in CH and from 12.3 to 35.5 mm in W (Purdy et al. 2001) as opposed to the teeth from the Gatun Formation which are much smaller. With regard to the ecology of H. serra, it is particularly abundant in neritic deposits containing warm-water faunas and scarce in deposits with cold-a dapted species (Cappetta 1987). The extant H. elongatus is a tropical coastal shark that inhabits in-shore and off-shore waters from 1 to 30 m depth (Compagno 1984). Family CARCHARHINIDAE Jordan & Evermann 1896 Genus GALEOCERDO Mller & Henle 1837 GALEOCERDO CUVIER Peron & Lesueur 1822 Common name: Tiger shark

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32 Referred Specimens: 18 isolated teeth; indeterminate position: UF 237901 237907, UF 241809 241812, UF 242818 242822, SMU 76456 and SMU 76466. Specific Locality: YPA017. Distribution: Miocene to recent. Miocene of USA (North Carolina and Florida), Brazil, Venezuela and Panama (this study). Pliocene of Italy, South Africa, and USA (North Carolina and Florida). Pleistocene of Celebes and Pleistocene of USA (Georgia). Extant G. cuvier has a cosmopolitan distribution (Compagno 1984; Cappetta 1987; Purdy et al. 2001; Aguilera & De Aguilera, 2001 2004; Dos Reis 2005; www.paleodb.org, 31 March 2009, using the name G. cuvier ). Description: The diagno stic characters of G. cuvier teeth include large and robust size and crown or apex slightly slanted; mesial edge rounded, with serrations at the base of crown, which is basally and apically straight, forming an obtuse angle; distal e dge has a pronounced notch, coarser serrations on the heel and base; V-shaped root, no central foramen (Figure 2-5). G. cuvier teeth are similar to those from Physogaleus aduncus but have a broader and larger crown and a more strongl y convex mesial cutting edge. G. cuvier teeth differ from Physogaleus contortus by the absence of very pronounced transverse groove and a thicker crown. G. cuvier teeth from the Gatun Formation meas ure 7.4 to 17.8 mm in CH and from 14.4 to 24.5 mm in W. A transverse groove is present in some, but not all teeth. Discussion: Extant Galeocerdo cuvier can reach lengths up to 7.5 m TL (Compagno 1984). Based on fossil material, G. cuvier probably grew to less than half this length in the past (Kent 1994). The teeth collected in the Yorktown Form ation, at Lee Creek Mine, North Carolina range from 13.5 to 29.1 mm in CH and 24.4 to 33.0 mm in W (Purdy et al. 2001), wh ich are larger than those found in the Gatun Formation.

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33 Regarding its ecology, G. cuvier is an opportunistic feeder; it eats a wide variety of marine life as well as taking carrion a nd a variety of inedible object s (Compagno 1984). Prey items vary from fish, marine reptiles, sea birds, marine mammals, and mollusks (Compagno 1988). Morphological features of its te eth, including its coarse serrati ons, are likely adaptations for slicing and ripping (Frazzetta 1988). G. cuvier is a coastal-pelagic tropical and warm -temperature shark (Compagno 1988), with tolerance for different marine ha bitats at depths from 0 to 140 m (Compagno 1984). It is very common in shallow waters during the night (Randall, 1992). Extant G. cuvier use shallow nearshore and offshore and estuarine waters as nursery areas (McC andless et al. 2007). Genus PHYSOGALEUS Cappetta 1980 PHYSOGALEUS CONTORTUS Gibbes 1849 Galeocerdo contortus (Gillette, 1984:177.) Galeocerdo contortus (Purdy et al. 2001:146) Common Name: Longtooth tiger shark Referred Specimen: One isolated toot h; indeterminate position: UF 237908. Specific Locality: YPA017. Distribution : Early to middle Miocene of USA (North Carolina. Maryland, Florida and Virginia), Italy (Marsili, 2007) and Panama (C appetta, 1987; Gillette, 1984; Hulbert et al., 2001; www.paleodb.org, 6 April 2009, using the name G. contortus ). Description: Teeth are very similar to the genus Galeocerdo with finely serrated, long, thick and warped crowns, pronounced notch and small serrations on heel of distal side; undulating margin and fine serrations on mesi al edge; U-shaped root with prominent protuberance on lingual face and tran sverse groove (Figure 2-6).

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34 P. contortus differs from the genus Galeocerdo by having a very prominent and bulging root with the deep notch. From lateral vi ew the expansion is much more erect in P. contortus teeth than Galeocerdo teeth (Leder 2005). P. contortus differs from P. aduncus in having a narrower, more apically erect a nd slightly twisted cusp and fine r distal serrations; a very large lingual protuberance and a flat basal surf ace on the tooth (Ward & Bonavia 2001).The P. contortus tooth from the Gatun Formation is 11.1 mm in CH and 15.5 mm in W. Discussion. P. contortus from Pungo River at Lee Creek Mine, North Carolina, range from 12 to 19 mm in CH. This species always occurs with Galeocerdo in Neogene localities along the east coast of the United States. Counts of specimens collected in Lee Creek Mine indicate that it is twice as common as Galeocerdo (Purdy et al. 2001). This is very different from the Gatun Formation where only one specimen ha s been identified. The occurrence of this species within the Gatun Formation extends its temporal range into the late Miocene. Purdy et al. (2001) compared the dentition of both P. contortus and Galeocerdo sp. and concluded that both species inha bited the same environments but did not compete for the same food resources. Both probably fed on a variety of bony fishes and rays, similar to lemon sharks ( Negaprion ), while the Galeocerdo fed on larger animals. Genus CARCHARHINUS Blainville 1816 CARCHARHINUS SP. Referred Specimens: 160 isolated te eth; uppers: UF 237990 237999, UF 238001 238018, UF 238020 238025, UF 238032, UF 24 1823 241825, UF 241827, UF 242825 242826, UF 242829, UF 242832, UF 242871; lowers : UF 241828, UF 241831 241832, UF 242823 242824, UF 242827 242828, UF 242830 242831, UF 242833, UF 242836, UF 242871, UF 237992, UF 237995, UF 237998 UF 237999; lateral: SMU 76475; indeterminate

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35 position: UF 238019, UF 241826, SMU 76457 76459, SMU 76463, SMU 76465, SMU 76469 and SMU 76472 76475 Specific Localities: YPA017, YPA020, YPA021 and YPA022. Distribution: The range of this genus extends from the early Eocene to Recent. Eocene of Pakistan, USA (Texas) and Egypt. Oligocene of USA (Florida) and Australia (Victoria). Miocene of Colombia (Pimiento, personal obser vation) Europe, North and West Africa, USA (California, Virginia, Maryland and Florida), Australia (Victori a), Japan (Shimane Prefecture), Panama, Mexico (Baja California), Argentina (Entre Rios), Peru (Ica), Venezuela (Falcon) and India (Gujarat). Pliocene of Australia (Tasmani a), Peru, Brazil, Pleist ocene of USA (Florida, California, and Georgia) Recent in all tr opical and temperate seas (Cappetta 1987; www.paleodb.org, 1 April 2009, using the name Carcharhinus sp.). Description: Diagnostic characte rs of upper teeth of the genus Carcharhinus include triangular shape, straight crown in anterior teeth a nd curved in laterals, flat labial face, slightly convex lingual face, serrated cutting edges, cusps separated or not from h eels; root can present a clear transverse groove in small forms (Figure 2-7A and B). Lower teeth have narrower cusps, crown well separated from heel, cutting edges serr ated, with a clear transverse groove (Figure 27C). Lower teeth of the genus Carcharhinus differ from Negaprion by having serrated cutting edges, Carcharhinus teeth differ from Sphyrna by having a thinner root and the lack of an expanded lingual heel. Carcharhinus differs from Galeocerdo by the absence of a strongly contorted crown, the lack of a large difference be tween mesial and distal cutting edge thickness and lengths, the absence of coar se serration in heels, and a thinner and non-bulged root. This

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36 genus is abundant in the Gatun Formation with teeth ranging greatly in sizes, from1.9 to 12.9 mm in CH and 4.1 to 17.6 mm in W (Figure 2-7). Discussion. Most species of Carcharhinus have teeth adapted for cutting and grasping (Kent 1994). Much taxonomic confusion exists within this genus (P urdy et al., 2001). The identification of individual Carcharhinus species based solely on is olated teeth is extremely difficult given the degree of convergence in toot h morphology. This problem is particularly acute in lower teeth, which are very similar among most species (Kent 1994). Factors influencing variation in tooth shape within the genus Carcharhinus include : variation among species, variation within a species, differences within individuals of a species (Naylor & Marcus 1994) and within a tooth row. Upper teeth have been documented up to 20 mm in CH (Cappetta 1987). CARCHARHINUS FALCIFORMIS Bibron 1841 (in Muller & Henle 1839-1841) Common name: Silky shark Referred Specimens: One isolated upper tooth: UF 241817. Specific Locality: YPA017. Distribution : Middle Miocene to Recent. Middle Miocene of USA (North Carolina). Miocene of Costa Rica and Pa nama (this study). Extant C. falciformis has a circumtropical distribution (Compagno1984; Laur ito 1999; Purdy et al. 2001; www.paleodb.org, 2 April 2009, using the name C. falciformis). Description: UF 241817 displays diagnostic ch aracters including triangular, narrow cusp, distal edge with angular notch pe rpendicular to the base with fine serratio ns; mesial edge is straight with a gap lack ing serrations at mid point, coarser se rrations at the base finer serrations at the apex, and root with well deve loped transverse gr oove (Figure 2-8).

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37 C. falciformis differs from other species of Carcharhinus by having a gap lacking serrations at the mid point of the mesial cutting edge. The C. falciformis specimen from the Gatun Formation is 7.2 mm in CH and ~6.4 mm in W. Even when this specimen has the edges a bit broken, it is possible to dist inguish a serrations gap (Figure 28) at the base of mesial side confirming the identification of this tooth as C. falciformis. Discussion: Purdy (2001) re ported this species from the middle Miocene Pungo River Formation at Lee Creek Mine, North Carolina. The only tooth described measured 14.2 mm in CH and 15.0 mm in W, which is twice as la rge as the Gatun specimen. Teeth in extant individuals vary in morphology, with some individuals not exhibiti ng the mid point gap discussed above (Figure 2-8) (Purdy et al. 2001). Regarding the ecology of extant C. falciformis, it is a large epipelagic shark that inhabits near shore, warm-shallow waters, from 18 to 500 m depth (Compagno 1984; Purdy et al. 2001). Females use shallow coastal waters as nursery areas (Alejo-Plata 2007). This species feeds mostly on bony fishes (Compagno 1984). CARCHARHINUS LEUCAS Valenciennes 1839 (in Muller & Henle 1839-1841) Common name: Bull shark Referred Specimens: 25 isolated teeth; uppers: UF 237979 237989, UF 237981, UF 237983 237989, UF 241829 241830 and UF 242838; lowers: UF 237980, UF 237982 and UF 237984. Specific Localities: YPA017 and YPA022. Distribution : Middle Miocene to Recent. Middle Miocene of USA (North Carolina and Florida). Late Miocene of Panama (this study). Pliocene of USA (Florida and North Carolina). Pleistocene of USA (Flori da and Georgia). Extant C. leucas with a circumtropical distribution

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38 (Compagno, 1984; Hulbert et al., 2001; www .paleodb.org, 2 April 2009, using the name C. leucas). Description: C. leucas teeth exhibit diagnostic characte rs including triangular, finely serrated crowns, serrations that become progressively coarser near the base of crown, mesial edge straight or slightly convex with a shallow or absent notch; distal edge more concave with a shallow notch, U-shaped root (Figure 2-9). C. leucas differs from other Carcharhinus species in having a mo re equilateral crown shape. C. leucas differs from C. longimanus by having a less elongated a nd thinner crown in the upper teeth and by having more sy mmetrical lower teeth. Some teeth have a well developed transverse groove. Lower teeth have thick crowns and cutting edges are finely serrated (Purdy et al. 2001). C. leucas from the Gatun Formation measure 7.5 to 10.7 mm in CH and 13.6 to 14.2 mm in W. Discussion: C. leucas from Pungo River Formation at Lee Creek Mine, North Carolina ranges from 17.0 to 20.0 mm in CH and 16.0 to 22.0 mm in W. These probably belong to individuals that were 2 to 3 m TL (Purdy et al., 2001), which are larger than individuals from the Gatun Formation. The extant C. leucas is a large epipelagic shark that is widespread in warm oceans, and also rivers and lakes (Compa gno 1988). It inhabits shallow (> 30 m depth) tropical and subtropical waters and feeds on bony fishes (Compagno 1984). C. leucas use shallow, low salinity, freshwater environments and estuar ies as nursery areas (Steiner et al. 2007). CARCHARHINUS OBSCURUS Lesueur 1818 Common name: Dusky shark

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39 Referred Specimens: Seven isolated teeth; uppers: UF 237915, UF 237917 237918 and UF 241818; lowers: UF 237916 and UF 242839. Specific Locality: YPA017. Distribution : Early Miocene to Recent. Early Miocen e of Venezuela, the Grenadines and Cuba. Middle Miocene of USA (Florida). Late Miocene of Panama (this study). Early Pliocene of USA (North Carolina). Late Pleistocen e of USA (Florida and Georgia). Extant C. obscurus is distributed in the Western and Eastern Atlant ic Ocean, the Mediterran ean, Indo-West Pacific Eastern Pacific: southern Califor nia, USA to Gulf of California (Hulbert et al. 2001; MacPhee et al. 2003; Portell et al. 2008; www.paleodb.org, 2 April 2009; www.fishbase.org, 3 of April 2009, using the name C. obscurus ). Description: C. obscurus teeth exhibit diagnostic characte rs including upper teeth with basal crown serrations coarser than the apex, nearly vertical dist al cutting edge, distal edge concave with convex apex and inclined distally (F igure 2-10). Lower teeth with erect crowns and straight or moderately arched root lobes. C. obscurus differs from other species of Carcharhinus by having coarser serrations at the base of the crown. C. obscurus have a thick root with a tran sverse groove and a broad crown. The lingual surface is flat whereas the labial surface is convex a nd they do not have cusplets. C. obscurus from the Gatun Formation measure from 7.7 to 10.1 mm in CH and from 11.2 to 16.28 mm in W. Discussion: C. obscurus from Yorktown Formation at Lee Creek Mine, North Carolina measure 17 to 22 mm in CH and from 18 to 25 mm in W. In extant individuals, sharks with corresponding tooth sizes are ~3 m TL (Purdy et al. 2001), suggesting that C. obscurus from the Gatun Formation were smaller in size.

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40 Regarding the ecology of this species, C. obscurus is common in coastal and pelagic, inshore and offshore, warm temperate and tropical shark of the continental and insular shelves and oceanic waters of 0 400 m of depth and feeds on bony fishes, other sharks, and invertebrates (Compagno 1984). Nursery areas are in shallow near-shore environments and occasionally estuaries (McCandless et al. 2007). CARCHARHINUS PEREZI Poey 1876 Common name: Caribbean reef shark Referred Specimens: 24 isolated teeth; uppers: UF 241819241820, UF 241822, UF 242840 242842, UF 242844 242846, UF 242848 242853, UF 242855 242857; lowers: UF 242845242846; indeterminate position: UF 241821, UF 241843, UF 241847 and UF 241854. Specific Localities: YPA017, and YPA022. Distribution: Early Miocene to Recent. Mi ocene of Brazil and the Grenadines. Early Miocene of Venezuela. Middle Miocene and USA (North Carolina). Late Miocene of Panama (this study). Early Pliocene of USA (North Carolina). Its extant distribution is restricted to the Caribbean (Compagno 1984; Dos Reis, 2005; Po rtell et al. 2008; www.paleodb.org, 2 April 2009, using the name C. perezi ). Description: C. perezi teeth demonstrate diagnostic charac ters that include high, narrow crown; distal edge inclined, well developed angular or rounded not ch; mesial edge straight or slightly convex, medium to coarse serrations (Figure 2-11). Lower teeth with straight crowns, finely serrated cutting edges a nd nearly straight root edges. C. perezi differs from other Carcharhinus species by having a coarsely serrated crown, an inclined distal side, and a straight mesial side. C. perezi have straight or oblique crowns, no cusplets, transverse groove weakly present. Some lateral teeth are slightly straight making them

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41 difficult to differentiate from lower teeth. C. perezi from the Gatun Formation range between 5.8 to 10.8 mm in CH and from 10.6 to 16.9 mm in W. Discussion: C. perezi from Lee Creek Mine, North Ca rolina measure 13.0 to 18.0 mm in CH and from 13.0 to 22.0 mm in W, which corresponds to sharks of 2 m TL (Purdy et al. 2001). This difference suggests that C. perezi from the Gatun Formation were represented by smaller individuals. Regarding the ecology of this species, extant C. perezi feeds on bony fishes (Purdy et al. 2001). They are reported from tropical waters f ound inshore of continenta l and insular shelves down to at least 30 m depth (Compagno 1984). C. perezi uses insular shallow reef systems as nursery areas (Garla et al. 2006). CARCHARHINUS PLUMBEUS Nardo 1827 Common name: Sandbar shark Referred Specimens: Five isolat ed teeth; uppers: UF 242858 242862 Specific Locality: YPA017. Distribution: Early Miocene to Recent. Early Miocene of Saudi Arabia. Middle Miocene of USA (North Carolina and Florida). Late Miocene of Panama (this study). Early Pliocene of USA (North Carolina). Early Pleisto cene of USA (Florida). Extant C. plumbeus has a circumtropical distribution (Compagno 1984; Hulbert et al 2001; www.paleodb.org, 3 April 2009, using the name C. plumbeus ). Description: C. plumbeus teeth exhibit diagnostic characters including: broad narrow crown, apically convex, fine to moderate serrations on edges, distal edge inclined with a well developed angular or rounded notch ; mesial edge straight or s lightly convex and thick root (Figure 2-12).

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42 C. plumbeus teeth are very similar to those from C. obscurus, but differ in having apical convexity in cutting ed ges (Purdy et al. 2001). C. plumbeus differs from C. albimarginatus by the absence of a hook at the apex (Purdy et al. 2001). C. plumbeus differs from C. perezi by having finer serrations and apical convexity. C. plumbeus may present a well developed transverse groove or a central foramen and a Ushaped root. Specimens from the Gatun Formation measure 6.8 and 10.6 mm in CH and 10.3 and 6.1 mm in W respectively. Discussion: C. plumbeus teeth from the Lee Creek Mine, North Carolina measure 14.0 to 19.0 mm in CH. Teeth of this si ze correspond to sharks of 2 m TL (Purdy et al. 2001). This suggests that C. plumbeus from the Gatun Formation were represented by smaller individuals. Regarding the ecology of this species, extant C. plumbeus individuals are coastal-pelagic sharks of warm temperate and tropical waters, found in insular and continental shelves and deep waters adjacent to them; and range from intert idal waters to 280 m in depth (Compagno 1984). C. plumbeus use estuarine or near-shore shallow warm waters for nurseries (McCandless et al. 2007). Genus NEGAPRION Whitley 1940 NEGAPRION BREVIROSTRIS Poey 1868 Negaprion eurybathrodon (Aguilera & De Aguilera, 2004:735) Common name: Lemon shark Referred specimens: 63 isolated teeth; indeterminate position: UF 237961 237978, UF 241813 241816, UF 241833241834, UF 242863242867, SMU 76455, SMU 76458 76459, SMU 76465, SMU 76469 and SMU 76474 76475. Specific localities: YPA017, and YPA020.

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43 Distribution: Eocene to Recent. Eocene of Pakistan and USA (Georgia). Miocene of Cuba, Italy, Saudi Arabia and USA (Nor th Carolina and Florida), Nigeri a, France, Portugal Venezuela, Ecuador and Panama (this study). Pliocene of USA (North Carolina, Georgia and Florida). Extant N. brevirostris is distributed in the Atlantic, incl uding the Gulf of Mexico and the Caribbean, and Eastern Pacific (Longbottom 1979; Cappetta 1987; Aguilera & De Aguilera 2001 and 2004; www.paleodb.org, 3 April 2009, using the names N. brevirostris and N. eurybathrodon; www.fishbase.org, 5 April 2009, using the name N. brevirostris ). Description: Teeth of N. brevirostris from the Gatun Formation demonstrate diagnostic characters including: a T-shaped, narrow crown perpendicular to th e root, crown not serrated, flat roots and transverse groove pr esent. Moderate ontogenetic he terodonty is observed in this species with smaller specimens lacking serrations on heels (Figure 2-13) while larger individuals exhibit them (Compagno 1984; Purdy 2001). Lower teeth of N. brevirostris differ from Carcharhinus by not having serrations on the crown. N. brevirostris can also demonstrate a slightly cu rved, inclined crown, elongated root lobes, strongly obtuse basal root angle, lingual face flat and labial face slightly convex. N. brevirostris from the Gatun Formation measure 3.7 to 13.7 mm in CH and from 4.3 to 16.3 mm in W. Discussion: Cappetta (1987) establishe d the maximum crown height of for Negaprion to be 20 mm. Purdy (2001) reported teeth in Lee Cr eek Mine, North Carolina measuring from 14 to 21 mm in CH and stated that in extant N. brevirostris teeth of this size are found in sharks 2.1 to 3 m TL, which is the size range for mature adults according to Compagno (1984). This suggests that sharks from the Gatun Formation were juve niles. In addition the lack of serrations on the heels of some specimens co rroborates this hypothesis.

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44 Regarding the ecology of this species, N. brevirostris inhabits inshore tropical and temperate estuarine and marine waters (Kent 1994). It occurs in intertidal zone down to at least 92 m depth. Prey items include bony fishes, stin grays, sea birds and invertebrates (Compagno 1984). This is a reef-associate d species that occurs on cont inental and insular shelves. N. brevirostris uses estuarine or near-shore, shallow, warm waters such as swamps or mangroves for nursery areas (McCandless et al. 2007). Genus RHIZOPRIONODON Whitley 1929 Isistius sp. (Gillette, 1984:179) Common name: Sharpnose shark Referred specimens: Three isolated teeth; indeterminate pos ition: SMU 76461, SMU 76464 and SMU 76475. Specific Locality: YPA017. Distribution : The range of this genus goes from the Eocene to Recent. Eocene of Pakistan, Egypt, Jordan and USA (Alabama, Georgia). Oligocene of USA (Florida). Miocene of USA (North Carolina), Venezuela and Costa Rica. Pliocene of USA (Florida). Recent species distributions in western Atlantic (including the Caribbean), easter n Atlantic and eastern Pacific (Compagno 1984; Laurito 1999; Hulbert et al 2001; Aguilera & De Aguilera 2004; www.paleodb.org, 6 of April 2009, using the name Rhizoprionodon sp.). Description: Rhizoprionodon sp. teeth display diagnostic ch aracters including: a slightly recurved crown, cutting edges finely serrated or smooth, mesial edge curved, distal heel with a notable notch, roots straight, low with a deep, transverse groove present (Figure 2-14).

PAGE 45

45 Rhizoprionodon sp. differs from Sphyrna by having a notch in di stal heel and shorter crown. Rhizoprionodon sp. from the Gatun Formation m easures between 2.5 and 3.3 mm in CH and 3.9 and 5.6 mm in W. Discussion: Cappetta (1987) stated that teeth from Rhizoprionodon are less than 4 mm in CH. Although, teeth from Lee Creek Mine measur ed 3.2 to 5.2 mm in CH and from 4.3 to 5.7 mm in W (Purdy et al. 2001). Total length in ex tant adult individuals averages about 1 m TL (Compagno 1984). This genus shows marked sexual dimorphism in body size, even though tooth morphology is not affected (Cappetta 1987). Species of this genus are main ly distributed in the Atlantic Ocean (together with the Caribbean Sea), including R. lalandii, R. porosus, and R. terranoenovae) (Compagno 1984). Regarding the ecology of this genus, based on the extant R. terranoenovae, it inhabits coastal warm, temperate, and tr opical waters, usually less than 10 m in depth (Compagno 1984). Nursery areas for this species are estuarin e, near-shore, warm, shallow environments (McCandless et al. 2007). Family SPHYRNIDAE Gill 1872 Genus SPHYRNA Rafinesque 1810 SPHYRNA SP. Common name: Hammerhead shark Referred specimens: 16 isolated teet h; upper: UF 242868; lower: UF 238020; indeterminate position: UF 242869 242870, SMU 76459, SMU 76463, SMU 76465 and SMU 76475. Specific Locality: YPA017.

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46 Distribution : The range of this genus goes from the Paleocene to Recent. Paleocene of USA (Maryland). Eocene of Pakistan and Togo. Mi ocene of USA (Florida, Maryland), Australia, Saudi Arabia, Mexico (Baja, Calif ornia), Austria, India (Orissa), Brazil, Venezuela and Panama (this study). Pliocene of USA (California) and Australia (South Au stralia). Recent distribution in all temperate and tropical seas (Cappetta 1987; Aguilera & De Aguilera 2004; Dos Reis 2005; Adnet et al. 2007; www.paleodb.org, 5 April 2009, using the name Sphyrna sp.). Description: Sphyrna teeth demonstrate diagnostic characters including crown labiolingually flattened, finely serrate d crown, apex inclined or slan ted distally, acute notch, thick, bulky root, deep transverse groove (Figure 2-15). Sphyrna sp. differs from Carcharhinus by having a thick bulky root. The mesial cutting edge of Sphyrna sp. is generally convex and slightly sigmoid. Cusps are slender and almost needlelike. Sphyrna sp. from the Gatun Formation has a thicker crown than the S. lewini and weaker serrations. This taxas measurements range from 3.1 to 8.9 mm in CH and 7.4 and 10.6 mm in W. Discussion: Cappetta (1987) established the maximum tooth si ze for this genus to be 20 mm in CH. This suggests that individuals from th e Gatun Formation were small. Extant species inhabit all temperate and tropical seas. They are found mostly in coastal waters and have a diet consisting of skates, rays, small sharks and bony fishes (Compagno 1988). SPHYRNA LEWINI Griffith & Smith 1834 Sphryna zygaena (Gillette, 1984:179) Common name: Scalloped hammerhead shark Referred specimens: Four isolated teeth; uppers: SMU 76454, SMU 76458 and SMU 76462; lowers: SMU 76449.

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47 Distribution: Middle Miocene to Recent. Middle Miocene of India. Late Miocene of Panama (this study). Pleistocene of USA (North Carolina). Extant S. lewini has a cosmopolitan distribution (Compagno 1984; www.paleodb.or g, 06 April 2009, using the name S. lewini ). Description: S. lewini displays diagnostic characters including: stout to slender crown, cutting edges either smooth or weakly serrate d, thick and bulky root and a deep transverse groove (Figure 2-16). S. lewini is differentiated from other Sphyrna species by having smooth to weakly serrated cutting edges. The S. lewini specimens from the Gatun Formation have a well-developed notch on the distal edges and the crowns are inclined. The teeth measurements range between 2.7 and 5.4 mm in CH and 5.2 to 11.0 mm in W. Discussion: This species is probably the most abundant hammerhead shark that occurs in coastal warm-temperate and tropical seas, ranging from the surface to at least 275 m in depth (Compagno 1984). Juvenile S. lewini usually occur close inshor e (Compagno 1984). Juveniles use estuarine or near-shore warm shallow wa ters as nurseries (McC andless et al. 2007). SPHYRNA MOKARRAN Rppell 1837 Common name: Great hammerhead shark Referred specimens: Four isolated teeth; uppers: UF 237909 UF 237912. Specific Locality: YPA017. Distribution: Early Miocene to Recent. Early Miocene of Cuba. Late Miocene of Panama (this study). Extant S. mokarran has a circumtropical distribution (Compagno 1984; www.paleodb.org, 6 April 2009, using the name S. mokarran).

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48 Description: S. mokarran exhibits diagnostic characters in cluding: triangular shaped, increasingly oblique crown, strongly serrated cu tting edges, thick and bulky root, and deep transverse groove (Figure 2-17). S. mokarran differs from other species of Sphyrna by having one heel more pronounced than the other. S. mokarran teeth from the Gatun Formation measure 7.6 to 9.4 mm in CH and from 9.6 to 16.4 mm in W. Discussion: This species is not well documented in the fossil record. It has only previously been reported from the Miocene of Cuba, although there is no desc ription of the specimens (MacPhee 2003). Regarding its ecology, this spec ies inhabits coastal-pelagic and semi-oceanic, tropical habitats. Nursery areas for S. mokarran are typically shallow and warm, estuarine or near-shore waters (McCandless et al. 2007). Discussion While our id entifications are consistent with those of Gillette (1984), there are a number of key differences and additions that expand our knowledge of ichthyofauna of the Gatun Formation. The presence of Ginglymostoma delfortriei, Carcharocles megalodon, Hemipristis serra Carcharhinus sp. and Physogaleus contortus are in agreement with th e descriptions of Gillette (1984). While no other Ginglymostoma teeth were collected duri ng the present study, the SMU specimens confirm their presence in the Gatun Fo rmation and agree with other reports from the Caribbean (Aguilera & De Agu ilera 2001; Laurito 1999). The fact that no other teeth were recovered during this study is not surprising, co nsidering that these t eeth are small and not typically found during surface collecting.

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49 Additional C. megalodon specimens were collected in the Gatun Formation during this study. The cosmopolitan nature of the species is documented by the presence of C megalodon teeth worldwide (Cappetta 1987; Purdy 1996; Pu rdy et al. 2001) including the Neotropics (Iturralde-Vinent 1996; Laurito 1999; Donovan & Gunter 2001; Nieves-Rivera 2003; Aguilera & De Aguilera 2001; Portell et al. 2008). The relatively small size of all the specimens found in Panama is notable, and will be addressed in future research (Pimiento et al., in progress). H. serra teeth are one of the most common shark fo ssils in the Gatun Formation; this is also consistent with other record s for the species, which is abunda nt in the Miocene and Pliocene of the Atlantic and Pacific basins (Cappetta 1987; Iturralde-Vinent et al. 1996; Laurito 1999; Purdy et al. 2001; MacPhee et al. 2003; Aguilera & De Aguilera 2001, 2004; Portell et al. 2008). The most common shark fossils found in the Gatun belongs to the genus Carcharhinus sp.; which is also reported in Venezuela (Aguilera & De Aguilera 2001) and Jamaica (Underwood & Mitchell 2004). This genus varies greatly in si ze and morphology being difficult to identify it to the species level. The presence Physogaleus ( Galeocerdo) contortus as reported by Gillette (1984) was confirmed by the collection of another specimen in this study. It should be noted, however that the specimens described in Gillette's work were not present in the SMU collection for comparison. This species is not very common in the Neotropics, although it has been reported in Cuba (Iturralde-Vinent et al. 1996) and the genus Physogaleus in Costa Rica (Laurito 1999). All of the species reported in this study that are consis tent with Gillette (1984 ), are also consistent with other Miocene assembla ges in the Caribbean Region. There are a number of key differences and additions to the icht hyofauna of the Gatun Formation resulting from this study. G illette (1984) identified one white shark (Carcharodon

PAGE 50

50 carcharias) tooth, describing it as being highly worn, missing its edges and serrations. However, this specimen was also missing from the SM U collection and I was unable to confirm his identification. Regardless, the presence of a whit e shark tooth in the late Miocene is unlikely, because C. carcharias specimens do not become common in the fossil record until the Pliocene (Ehret et al. 2009). Without being able to view the specimen, it is difficult to speculate what species is represented by this tooth. The original description lacks enough de tail to be confident, but it could be also at tributable to a small C megalodon or perhaps Cosmopolitodus ( Isurus ) hastalis, although the latter species lacks serrations. The current hypothesis regarding the evolution of the white shark places C hastalis as an ancestral taxon to C carcharias One of the most obvious morphological diffe rences between the taxa is the lack of serrations in C hastalis and the presence of coarse serrations in C carcharias Transitional forms between the two are found throughout the Pacific Basin during the la test Miocene (De Muizon & DeVries 1985; Ehret et al. In Prep.). In the Neotropics during the Miocene, Cosmopolitodus ( Isurus) hastalis has been reported in the Cuba (Iturralde-Vinent et al. 1996); Isurus sp. in Venezuela (Aguilera & De Aguilera 2001), C. retroflexus in Costa Rica (Laurito 1999) and I. oxyrinchus in the Grenadines (Portell et al. 2008). However, neither Cosmopolitodus nor Isurus has been recovered from Panama. The absence of this taxon in the sha llow-water Gatun Formation may be due to the bathyal or mesopelagic depth range of th is species (Aguilera & De Aguilera 2001). Additional omissions in our study relative to Gillettes (1984) original description include the absences of the species Physogaleus ( Galeocerdo) aduncus, Sphyrna arambourgi Sphyrna zygaena and Isistius sp. These differences reflect the reanalysis and re-description of the original materials. The teeth from the SMU collecti on w ere not catalogued until this study, making the identification of the individual specimens desc ribed by Gillette (1984) somewhat problematic.

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51 The teeth that Gillette (1984) referred to as S. arambourgi and S. zygeana have been reidentified as S. lewini in this study. The shape and characteri stics of these fossil teeth are more consistent with S. l ewini than either S arambourgi or S. zygaena. Finally, the presence of Isistius sp. in the Gatun Formation is refuted. The specimens referred to Isistius sp. by Gillette (1984) belong to the sharpnose shark, Rhizoprionodon. While lower Isistius teeth are present in the Miocene of Ve nezuela (Aguilera & De Aguilera 2001) and in the Pliocene of North Carolina (Purdy et al. 2001) and Florida (G. Hubbell, Pers. Comm., 2009), no upper teeth have been described from the fossil record, which may be related to their weaker mineralization (Cappetta 1987). Th e re-identification of these teeth to Rhizoprionodon is also more consistent with the habitat reconstruction of the Gatun Formation. Rhizoprionodon has been reported from the Miocene of the Caribbe an (Aguilera & De Aguilera 2004; Laurito 1999); in addition, it inhabits coas tal, warm waters, whereas Isistius tends to be an oceanic, epipelagic to bathypelagic shark (Compagno 1984; Purdy et al. 2001). Therefore, given what is known of the other taxa of invertebrates and sharks, its presence in the Gatun Formation would be highly irregular. Additional species that have been identified from the Gatun Formation of Panama (see in Table 2-2) are mostly shared with other Miocene assemblages in the Caribbean region and include: G. cuvier, also reported in the Miocene of Ven ezuela (Aguilera & De Aguilera 2001); C. falciformis also reported in Costa Rica (Laurito 1999); C leucas ; C obscurus also reported in Cuba (Iturralde-Vinent et al. 1996 ; MacPhee et al. 2006) and the Gr enadines (Portell et al. 2008); C perezi also reported in the Grenadines (Portell et al. 2008); C plumbeus; Negaprion brevirostris also reported in Venezuela (Aguilera & De Aguilera 2001) and Cuba (IturraldeVinent et al. 1996; M acPhee et al. 2006); Sphyrna sp., also reported in Venezuela (Aguilera &

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52 De Aguilera 2001); S. lewini and S. mokorran, also reported in the Mi ocene of Cuba (IturraldeVinent et al. 1996; MacPhee et al. 2006). Based on the time distribution of the taxa found in the Gatun Formation, their teeth measurements (Table 2-1) and their ecology (Tab le 2-2); different assumptions can be made regarding their longe vity, sizes and habitat preferences. Taxonomic Longevity W ithin the 16 taxa identified (Table 2-2) from the ~10 million years old late Miocene Gatun Formation, four species ar e now extinct (see in Table 22) and the remaining 12 still exist today; the latter indicating the presence of relatively long-lived taxa. Sharks are very successful group that have been common in our oceans for 400 million years (Hubbell 1996). Some of the genera represented in the Gatun Formation first appe ar in the fossil record in the Paleocene (~65 Ma), others in the Eocene (~ 55 Ma) and the largest number have been around since the Miocene (~20 Ma). Those taxa have no t changed for several million years and at least their tooth morphology remains sim ilar to extant individuals. The closure of the Isthmus of Panama ~4 m illion years ago resulted in a major geographic and environmental changes, and consequent vica riance of once continuous faunas. This was a key event for tropical biotic ev olution, allowing for the interchange of terrestrial species between North and South America and also isolating Pacific and Atlantic marine organisms (Cronin & Dowsett 1996). The late Miocene Gatun Formati on is represented by many long-lived shark species that survived the formation of the Isthmu s of Panama, as opposed to several other species of that became extinct due to the effects of this event (O'd ea et al. 2007; Budd et al. 1996). Size The tooth-size com parisons were made when possible with measurements of specimens from two formations within the Lee Creek Mine Aurora, North Carolina (Purdy et al. 2001): The

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53 Pungo River Formation (middle Miocene) and the Yorktown Formation (early Pliocene; Ward & Bohaska 2008). These formations are respectiv ely older and younger than the late Miocene Gatun Formation age range (12-8.4 million years ago; Coates 1996a), and consequently reduce any potential variation arising from macroe volutionary shifts in body sizes through time. Based on the size of the isolat ed teeth found within the Gatun Formation, I interpret that the sharks inhabiting Panama during the late Mioc ene were small overall. Extant related species use shallow environments similar to the late Mi ocene Gatun Formation as nursery area (Table 22); however, I cannot conclude they were all juveniles usi ng this area as a nursery ground without studying the ont ogenetic changes of every species (i.e. lateral teeth of juvenile Hemipristis serra have reduced or no serrations in th e mesial edge and an unserrated tip (Compagno 1988)). Habitat Preferences Previous studies of the Gatun Formation indica te that this area was a shallow-water seaway between the Pacific Ocean and th e Caribbean Sea, with depths between 20 to 40 m and salinity conditions similar to those found in large bays (Coates & Obando 1996; Teranes et al. 1996). Based on depth preferences of extant and relate d shark species to those occurring in the Gatun Formation, I also believe that this area was a shallow environment during the late Miocene (Figure 2-18). Many of the shark sp ecies that inhabited this envir onment occurred in the nerictic zone, below 150 m depth (dashed line). Taxa with depth preferences deeper than 150 m are not commonly found in the Gat un Formation including C. falciformis (1 specimen), C. obscurus (6 specimens), C. plumbeus (5 specimens), and S. lewini (4 specimens). In addition, the absence of other pelagic fauna commonly found in Mioc ene assemblages of the region such as Alopias, Cosmopolitodus and odontaspids (Portell et al. 2008; Aguilera & De Aguilera 2001; Ward &

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54 Bonavia 2001; Iturralde et al. 1996; Laurito 1999) in the Gatun Formation also supports the hypothesis of the shallow-water seaway. Studies of benthic foraminifera (Collins et al. 1996) from the Gatun Formation show a strong Caribbean affinity. However, most of the shark genera found in the Gatun Formation have related modern species that ar e found in both the Pacific Ocean and the Caribbean Sea (Gillette 1984). On the other hand, one species described here ( C. perezi) is currently restricted to the Caribbean Sea (Compagno 1984). This sa me trend is also apparent in Rhizoprionodon ; the genus has extant representatives mainly distributed in the Atlantic Ocean ( R. terranovae, R. lalandii, and R. porosus ) (Compagno 1984). These sharks inhabited the shallow seaway that was located in what is today Panama during the late Miocene and were able to move freely between the Caribbean and the Pacific. After the formati on of the Isthmus of Pa nama during the early Pliocene, ~3.5 to 4 million years ago they then became restricted to the Caribbean Sea. The closure of the isthmus was not a single event and its biological effects on marine organisms are likely to have occurred over several million years (Coates & Obando 1996). After the formation of the Isthmus of Panama, diversifi cation influenced by the increase of the habitat complexity associated with this event occu rred (Jackson & Budd 1996). In this study, 16 fossil taxa that lived in the shallow seaway that was located in Panama during the late Miocene were identified. Today, approximately 46 shark species are found on both side s of the Isthmus of Panama (data retrieved from FishBase, see Ap endix 1). The results shown in this study significantly improve our knowledge on the Neotropics shark fauna and provide a guideline to address further questions about the sharks biodi versity of Neotropics and the effects of the formation of the Panamanian isthmus on sharks fauna.

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55 Figure 2-1. Graph showing the number of teet h collected in the Gatun Formation using 2 different techniques. Every number in the xaxis represents a ta xon (see Table 2-1) ordered from the smallest to the larger teeth. White columns are the teeth collected by surface prospecting. Black columns are the te eth collected by Gillette (1984) using screenwashing.

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56 Figure 2-2. Ginglymostoma delfortriei from the late Miocene Gatun Formation, Panama, SMU 76470, indeterminate position. Figure 2-3. Carcharocles megalodon from the late Miocene Gat un Formation, Panama. A. UF 237950, largest anterior tooth. B. UF 237914, lateral tooth of a juvenile (with cusplets). C. UF 237959, sm allest anterior tooth.

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57 Figure 2-4. Hemipristis serra from the late Miocene Gatun Formation, Panama. A. UF 237941, upper largest tooth. B. UF 237924, upper smallest tooth. C. UF 242806, largest complete lower tooth. D. SMU 76467, smallest lower tooth. Figure 2-5. Galeocerdo cuvier from the late Miocene Ga tun Formation, Panama, UF 237902, indeterminate position. Figure 2-6. Physogaleus contortus from the late Miocene Gat un Formation, Panama, UF 237908, indeterminate position.

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58 Figure 2-7. Carcharhinus sp. from the late Miocene Ga tun Formation, Panama 1. UF 232004, upper tooth. 2. SMU 76475, smallest tooth (lateral). 3. UF 281828, lower tooth. Figure 2-8. Carcharhinus falciformis from the late Miocene Ga tun Formation, Panama, UF 241817, upper tooth. Gap of serrations in mesial side is diagnostic for this species.

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59 Figure 2-9. Carcharhinus leucas from the late Miocene Gatun Formation, Panama, UF 241829, upper tooth. Figure 2-10. Carcharhinus obscurus from the late Miocene Gatun Formation, Panama, UF 242839, upper tooth. Figure 2-11. Carcharhinus perezi from the late Miocene Gatun Formation, Panama, UF 242851, upper tooth.

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60 Figure 2-12. Carcharhinus plumbeus from the late Miocene Ga tun Formation, Panama, UF 242860, upper tooth. Figure 2-13. Negaprion brevirostris from the late Miocene Gatun Formation, Panama, UF 241814, indeterminate position. Figure 2-14. Rhizoprionodon sp. from the late Miocene Gatun Formation, Panama, SMU 76475, indeterminate position.

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61 Figure 2-15. Sphyrna sp. from the late Miocene Gat un Formation, Panama, UF 242868, upper tooth. Figure 2-16. Sphyrna lewini from the late Miocene Gatun Formation, Panama, SMU 76458, upper tooth. Figure 2-17. Sphyrna mokarran from the late Miocene Ga tun Formation, Panama, UF 237912, upper tooth.

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62 Figure 2-18. Estimated paleodepth of the Gatun Fo rmation based on depth preferences of extant and related shark species. Many of the shark species occurred below the 150 m (dashed line), i.e., all in th e neritic zone. Taxon number refers to the numbers in Table 2-2 ordered as appear in text.

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63 Table 2-1. Number of specimens when two diffe rent collection methods employed in relation with teeth CH. Taxa CH Size range (mm) # Prospecting # Screenwashing Total 1 Carcharhinus sp 1.9-12.9 58 98 156 2 Rhizoprionodon sp 2.5 3.3 0 3 3 3 Sphyrna lewini 2.7 5.4 0 4 4 4 Sphyrna sp. 3.1 8.9 4 12 16 5 Negaprion brevirostris 3.7 13.7 29 34 63 6 Ginglymostoma delfortriei 5 0 3 3 7 Hemipristis serra 5.4-21.6 52 1 53 8 Carcharhinus perezi 5.8 10.8 22 0 22 9 Carcharhinus plumbeus 6.8 10.6 5 0 5 10 Carcharhinus falciformis 7.2 1 0 1 11 Galeocerdo cuvier 7.4-17.8 15 2 17 12 Carcharhinus leucas 7.5-10.7 14 0 14 13 Sphyrna mokarran 7.6 9.4 4 0 4 14 Carcharhinus obscurus 7.7 10.1 6 0 6 15 Physogaleus contortus 11 1 0 1 16 Carcharocles megalodon 16-54 19 0 19 Total 230 157 387 Taxa numbers ordered from the smallest to the largest teeth

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64 Table 2-2. Paleoecology and inferred habitats of the elasmobranch fauna from the Gatun Formation; late Miocene of Panama. Ecology Taxa Time Distribution Habitat Nursery areas 1 Ginglymostoma delfortriei Miocene Near-shore, 0 to 130 m Estuarine or near-shore, shallow environments 2 Carcharocles megalodon Miocene to Pliocene Coastal habitats Warm-water areas 3 Hemipristis serra Miocene to Pliocene Neritic, warm waters, 1 to 30 m Not known 4 Galeocerdo cuvier* Miocene to Recent Coastal-pelagic, warm waters, 0 to 140 m Shallow near-shore and offshore and estuarine waters 5 Physogaleus contortus Early to middle Miocene Coastal-pelagic, warm waters, assumed to be same as G. cuvier Not known or assumed to be same as G. cuvier 6 Carcharhinus Early Eocene to Recent Shallow waters Not applicable 7 Carcharhinus falciformis* Middle Miocene to Recent Epipelagic, near shore, warm-shallow waters, 18 to 500 m Shallow coastal waters 8 Carcharhinus leucas* Middle Miocene to Recent Epipelagic, rivers and lakes, warm waters, 0 to 30 m Shallow coastal waters 9 Carcharhinus obscurus* Early Miocene to Recent Coastal and pelagic, warm waters, 0 400 m Near shore, shallow environments and occasionally estuaries 10 Carcharhinus perezi* Early Miocene to Recent Inshore of continental and insular shelves, warm waters, 0 -30 m Insular shallow reef systems 11 Carcharhinus plumbeus* Early Miocene to Recent Coastal-pelagic, warm waters, 0 280 m Estuarine or near-shore, shallow, warm waters 12 Negaprion brevirostris* Eocene to Recent Inshore, estuarine and marine waters, 0 92 m Estuarine or near-shore, shallow, warm waters such as swamps or mangroves 13 Rhizoprionodon* Eocene to Recent Coastal warm waters, usually less than 10 m Estuarine, near-shore, warm, shallow environments 14 Sphyrna* Paleocene to Recent Coastal waters Not applicable 15 Sphyrna lewini* Middle Miocene to Recent Coastal warm waters, 0 275 m Estuarine or near-shore shallow, warm waters 16 Sphyrna mokarran* Early Miocene to Recent Coastal-pelagic and semi-oceanic, warm waters 1 80 m Estuarine or near-shore shallow, warm waters Indicates new reports for Panama. Taxa numbers ordered in phylogenetic order as it is in text.

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65 CHAPTER 3 ANCIENT NURSERY AREA FOR THE EXTINCT GIANT SHARK MEGALODON ( CARCHAROCLES MEGALODON ) IN THE MIOCENE OF PANAMA Introduction Sharks, especially large s pecies, are highly m obile organisms with a complex life history and wide distribution. During their lifetime they generally utilize three types of areas: adult feeding, reproduction and nurseries (Plata et al. 2007). In modern species, nursery areas are historically defined by the presen ce of gravid females and free-swim ming neonates. It is also an area that can be shared by several shark spec ies, where young sharks spend their first weeks, months or years (Castro 1993). More recent studie s have defined nursery areas as geographically discrete essential zones for sh ark survival that provides them with two types of benefits: protection from predation (mainly larger sharks (Castro 1993)); and abundant food resources (Heupel et al. 2007). Productive, shallow-water ecosystems thus provide sharks significant protection from larger predators a nd/or abundant food (Heithaus 2007). The Gatun is a highly fossiliferous Neogene formation located in the Isthmus of Panama (Figure 1-1) with a diverse fauna of sharks (B lake 1862; Gillette 1984; Pimiento et al. 2010). Studies of different taxa, including the exceedingl y diverse molluscan fauna, indicate that it was a shallow-water ecosystem (~ 25 m depth) wi th higher salinity, mean annual temperature variations, seasonality and productivity relative to modern sy stems in this region (~10Ma) (Coates 1996a). Studies of differe nt taxa indicate that it was a shallow-water ecosystem (~ 25 m depth) with higher salinity, mean annual temper ature variations, seasonality and productivity relative to modern systems in this region (Collins et al. 1996; Coates & Obando 1996; Teranes et al. 1996; Gussone et al. 2004; Haug et al. 2001). Over the past 20 years, the Gatun Formation localities have been extensivel y used to extract sediment fo r construction. During the more recent years, these extraction ac tivities have increased substantially. Based on our observations

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66 made during the two past years of fieldwork, we predict that these outcrops will soon likely be excavated completely. Therefore it is timely and urgent to study the fossils occurring in these outcrops before they are no l onger available to science. Fossil sharks were first reported from Pa nama in 1862 (Blake 1862). In 1984, the first description of the elasmobranchs from the Ga tun Formation was published (Gillette 1984). More recently, the biodiversity of the fossil sharks from the Gatun is documented on a large new collection consisting of 16 recognizable taxa. Th is work also included paleoecological and paleodepth analyses that supported the interpreta tion of the paleocology of the Gatun Formation as shallow-water habitat (Pimiento et al. 2010). Although is not very common, the extinct Carcharocles megalodon (Agassiz 1843) is one of the species that occurs in the Gatun Formation. The taxonomic assignment of this species has been debated for nearly a centur y, and there are three possible in terpretations: (1) Some authors place C. megalodon and other megatoothed sharks with the extant white shark ( Carcharodon carcharias ) in the same genus ( Carcharodon) and therefore the same family (Lamnidae) (Applegate & Espinosa-Arrubarren a 1996; Gottfried et al. 1996; Purdy 1996). (2) Other authors place C. megalodon and megatoothed sharks in a different genus (Carcharocles) and family (Otodontidae) (Jordan & Hannibal 1923; Casier 1960; Gluckman 1964; Cappetta 1987, Ward & Bonavia 2001; Nyberg et al. 2006; Ehret et al. 2009). Although minority po ints of view, some workers recognize (3) megatoothed sharks as a series of chronospecies of the genus Otodus and place all megatoothed sharks except C megalodon in this genus. Furthermore, C megalodon is assigned to the genus Megaselachus, based on the loss of lateral cusplets (Zhelezko & Kozlov 1999). Of relevance of this study, we follow the second hypothesis; that Carcharocles megalodon and Carcharodon carcharias belong to separate genera in different families.

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67 However, both species belong to the order Lamnif ormes, and in the absence of living members of the Otodontidae, C carcharias should be regarded as an analogous species to C. megalodon. We base this analogy on the presumed similariti es in body shape, feeding habits, and overall tooth and vertebra l centrum morphology. C. megalodon is widely regarded as the largest sh ark to have ever lived. Based on tooth crown height (CH), this giant r eached a total length (TL) of more than 16 m. One single tooth can exceed more than 168 mm of total height (Gottfried et al. 1996). The diagnostic characters of C. megalodon teeth include: large size, triangular shape, fine serrati ons on the cutting edges, a convex lingual face, a slightly convex to flat labi al face, and a large neck (Pimiento et al. 2010). Juvenile specimens of C. megalodon can have lateral cusple ts (Applegate & EspinosaArrubarrena 1996), or not (Ward & Bonavia 2001). Th e size and shape of the teeth vary within the jaw: Anterior teeth are large and symmet rical whereas the latero-posterior teeth are asymmetrical with slanted crowns Moving antero-posteri orly through the jaw, there is a slight initial increase in size on either side of the mid-line, followed by a progressive decrease that continues to the last tooth (e.g. Purdy et al. 2001) (Appendix C). Fossil teeth of C. megalodon range in age from 17 to 2 Ma (middle Miocene to Pleistocene) and have a cosmopolitan distribution (Pimiento et al. 2010; Gottfried et al. 1996; Purdy 1996). It has been suggested the megatoothed Carcharocles used warm-water areas for nurseries (Purdy 1996). Two nursery areas have previously been proposed for this genus: the late Oligocene Chandler Bridge Formation of South Carolina, based on the abundance of juvenile Carcharocles teeth, accompanied by fossils of presumed prey species (Purdy 1996); and the Paleocene Williamsburg Formation of South Ca rolina, based on the presence of juvenile C. orientalis teeth in a shallow marine environmen t (Purdy 1998). However, neither of the

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68 collections form these two localities have been rigorously analyzed and thus the presence of paleo-nurseries remained anecdotal until the present report. Previously proposed nursery areas for the mega-toothed Carcharocles have been mainly assigned based on the presence of juvenile teeth along with small odontocete and mysticete skulls, which are assumed to be their prey species (Purdy 1996). De spite extensive field collecting, marine mammals have not been found in the Gatun Formation so far. Thus I assert that the small size of teeth found in the Gatun Fo rmation may also relate to the absence of large prey species that would have likely been required for larger indivi duals to have existed in this shallow-water habitat. The presence of mammals as potential prey do es not represent an evidence of a shark nursery area. As is known from modern studies of sharks, the main purpose of the nursery areas is not feeding (Castro 1993; He ithaus 2007; Heupel et al. 2007; Pl ata et al. 2007). Studies have shown that some shark species do not consume large quantities of food during their juvenile stages (Bush & Holland 2002; Lowe 2002). Even when nursery areas provide ample food resources for juvenile sharks, some species select these habitats more for predator avoidance and not food consumption (Heupel et al. 2007; Heithaus 2007). Furthermore, some shark species (Lowe et al. 1996; Yamaguchi & Taniuchi T 2000 ; Ebert 2002; McElroy et al. 2006) present an ontogenetic shift in its feeding patterns. For example, the lamnoid white shark ( C. carcharias ) (Tricas & McCosker 1984; Estrada 2006) feeds on fishes during their juvenile stage and on mammals during their adult stage. Marine mammals have not been found in the Gatun Formation so far. On the other hand, bony fish otoliths are abundant and represent a food source for the marine fauna that lived in this diverse environment (Aguilera & De Aguilera 1996).

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69 In this study, Carcharocles megalodon teeth were collected and measured from two localities within the Gatun Formation of Pana ma. Surprisingly, large teeth are uncommon with specimens recovered having crow n heights ranging between 16 to 72 mm. The objective of this work is to determine if the late Miocene Gatun Formation was used as a nursery area by young C. megalodon. Accordingly, we compared the tooth sizes from the Gatun Formation with those found in older and younger formations to determin e if the smaller size di stribution observed is unique to the species duri ng the late Miocene. In addition, we compared these sizes with tooth sets from individuals of different life stages to determine if the small size observed is related to age, or position within the jaw. Finally, we calculated the total length of all C. megalodon individuals based on tooth crown height from the Gatun Formation to estimate the life stage based on overall body size. The results obtaine d in this study from tooth measurement comparisons and individual total length estimates allowed us to determine the age class/size of individuals that inhabited the sh allow-water habitats of the late Miocene Gatun Formation, ~10 million years ago. Materials and Methods Carcharocles megalodon teeth are relatively rare in th e Gatun Form ation. Of more than 400 teeth of fossil sharks collected from the Gatun Formation between 2007 and 2009 representing 16 taxa, a total of 28 specimens (Appendix D) of C. megalodon have been collected. Fossils do not provide a record of life as comp lete as when studying living organisms. For that reason and also because of the rar ity of this species in the area of study, we consider our sample size adequate. In addition, it is urge nt to study the fossils of a form ation that will soon disappear due to the increasing excavations. The two localities studied in the Neogene ma rine sediments of the Gatun Formation of Panama (Figure 1-1), crop out in a broad area in north-central Pa nama and has been proposed to

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70 be late Miocene, spanning from about 12 to 8.4 Ma (Collins et al. 1996 ). The materials were collected mainly by surface pros pecting by the Panama Canal Proj ect Field Team of the Center of Tropical Paleobiology and Archaeology (CTPA) of the Smithsonian Tropical Research Institute (STRI), as well as the University of Florida (UF) scientists. Some of the specimens collected are deposited in the Florida Museum of Natural History (FLMNH) and are designated with a UF catalogue number which are available in its database: http://www.flmnh.ufl.edu/databases/VP/intro.htm The remaining specimens are designated with a CTPA or AT number and are part of the STRI collection. Crown height (CH) and width (W) of all spec imens were measured in millimeters (Figure 2-1, Table 3-1). In order to calculate dimensions of inco mplete specimens, W vs. CH measurements were plotted and a line regres sion was calculated (Appendix E). Measurements were then compared with isolated teeth from geologically younger and older collections and finally the specimens total lengths were calculated based on their CH. Temporal Comparisons of Similar Faunas Isolated teeth from the younger Bone Valley Fo rmation, Florida (early Pliocene, ~5 Ma) (Morgan 1994; Tedford et al. 2004), from the Vertebrate Paleontology Co llection at the FLMNH in Gainesville, Florida; were measured (A ppendix F) and compared with the Gatun teeth. Additionally, isolated teeth from the older Ca lvert Formation, Maryland (middle Miocene, ~14 Ma) (Morgan 1994), from the Vertebrate Paleonto logy Collection at the NMNH, in Washington, D.C.; were also measured (Appendix G) and then compared with the Gatun Formation teeth. Life Stage Comparisons Two C. megalodon associated tooth sets of different life stages from the Hubbell collection at Gainesville, FL were measured and compared with tooth sizes of the Ga tun isolated teeth. The juvenile tooth set is from the Bone Valley Fo rmation, Florida (early Pliocene) (Morgan 1994;

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71 Tedford et al. 2004) (Appendix H) The adult tooth set is from the Yorktown Formation, North Carolina (early Pliocene) (Ward & Bohanska 2008) (Appendinx I). Total Length Estimates As described above, the extant white shark ( Carcharodon carcharias), h as been used as a general morphological analog for the extinct Carcharocles megalodon. Likewise, previous studies have asserted that teeth of C. carcharias can be used to estimat e the total length of C megalodon (Gottfried et al. 1996; Shimada 2003). Based on C. carcharias tooth height and total length ratios, I have measured C. megalodon crown height to extrapolate its total length estimates based on the work of Shimada ( 2006), where every tooth position in the jaw corresponds to one regression e quation that calculates its bod y size (Appendix J). I assigned a range of possible positions to the Gatun teeth and estimated the TL of every specimen by calculating it from the average among the differe nt positions where every tooth could have belonged (Mean TL, Table 3-1). Furthermor e, I inferred the life stage of every C. megalodon, by extrapolating it from the relationship between body size and life stage in C. carcharias following Gottfried et al. (1996). I based our C. megalodon estimates on extrapolations from the extant C. carcharias given their similarities in body shape, feeding habits, and tooth and vertebral morphology. In addition, both species belong to the same order (Lamniformes), and in the absence of living members of C. megalodons family (Otodontidae), C carcharias is the only analogous species available. Results and Discussion Temporal Comparisons of Similar Faunas In m any clades represented in the fossil r ecord, animals oftentimes show a general tendency to become larger through time, i.e., also called Copes Rule (MacFadden 1992; Hone & Benton). For example, there is a trend toward s increasing size of species within the genus

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72 Carcharocles from C. auriculatus to C. agustidensis to its larger form, C. megalodon (Purdy 1996). However, there is no evidence of such a microevolutionary trend in the single species C. megalodon through time, as is shown below. In order to know if the small size observed in the fossil C. megalodon from the Gatun Formation is a special feature during the late Miocene in a potentially chronoclinally evolving species, we performed tooth size comparisons through time within ot her marine faunas that have sufficiently large numbers of specimens of C. megalodon. Given the fact that the C. megalodon from the Calvert Formation of Ma ryland are older (~14 Ma) and the C. megalodon from the Bone Valley Formation of Florida are younger (~5 Ma), comparing these populations with C. megalodon from the Gatun Formation can determine if there is a long-term, chronoclinal trend for size increase, or if C. megalodon from the Gatun Formation are unusually small. Figure 3-1 shows that both large and small tooth sizes are found in the faunas older and younger than the Gatun Formation, and thus there is no observed microevolutionary trend for increased size in C. megalodon over time. I therefore assert that the sma ll size observed in the Gatun Formation is not related to microevolutionary shifts in body size. Consequently, I demonstrate stasis in body size within the species C. megalodon, which provides us important context in which to compare ancient populations from th e localities described above. Life Stage Comparisons Is it known that within an individual, C. megaoldon teeth vary in size within the jaw (e.g. Applegate & Espinosa-Arrubarrena 1996; Purdy 1996; Purdy et al. 2001) (Appendix C). It could therefore b e argued that the small size observe d in the Gatun Formati on is related to tooth position, rather than juvenile life st age of the individuals. In order to test this, we compared tooth sizes of the Gatun Formation specimens with associ ated tooth sets from individuals of different life stages (juvenile and adult) fr om other localities. Our results i ndicate that most teeth from the

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73 Gatun Formation are close to the observed range of a juvenile de ntition (Figure 3-2), regardless of tooth position within the jaw. Comparing the Gatuns isolated teeth with t ooth sets of individuals from different life stages helps to determine if th e tooth size observed is related w ith tooth position. Nevertheless, in order to determine the life stage of those an imals were neonates, juve niles or adults; it is necessary to establish total length estimates as well, as presented below. Total Length Estimations The tooth size com parisons made in this research suggest that the small size of C. megalodon teeth from the Gatun Formation is not re lated to temporal differences within a chronoclinally evolving species (a s described above), but rather they may belong to juvenile sharks. When only the teeth of a shark species are preserved, life stages of individuals can be predicted in two different ways: (1) studying mor phological features of the teeth during juvenile stages; and (2) extrapolating total length us ing the relationship betw een body size and crown height. (1) In C. megalodon teeth of juveniles sometimes dem onstrate lateral cusplets (Applegate & Espinosa-Arrubarrena 1996; Ehret et al. 2009). For example, UF 237914 (a lateral tooth) exhibits lateral cu splets and is assumed to be from a juvenile. On the other hand, UF 237959 (a lower anterior tooth) and UF 23794 9 (an upper anterior) are both very small teeth that exhibit no lateral cusplets (Appendix D). The latter teeth are thick, heart-shaped, and are considered to represent embryonic Megalodon teeth (G. Hubbell, pers. communication). These teeth retain the morphology of the species even at small sizes and do no demonstrate late ral cusplets (Ward & Bonavia 2001).

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74 (2) Gottfried et al. (1996) made inferences about the skeletal anatomy of C. megalodon based on comparisons with ontogene tic trends in the white shark, C. carcharias. They deduced that a C. megalodon fetus could reach ~ 4 m, juveniles ~14 m, and adults ~17 m. Based on crown heights and following the work of Shimad a (2003), I estimate th e total lengths of C. megalodon specimens from the Gatun Formation (Table 3-1). Based on Gottfried et al.'s inferences, the total length estimations made in this research suggest that the C. megalodon specimens from the Gatun Formation represent mostly juveniles, with total lengths less than 14m, while one specimen is interpreted as an adult, with an estimated total length of 17m (Figure 3-3). Concluding Remarks: Nursery Area Hypothesis In this study I show that th e sm all tooth size observed in C. megalodon from the Gatun Formation is not related to its temporal positi on within a chronoclinally evolving species, or paucity of large prey species. Thus, the C. megalodon from the Gatun Formation indicates the dominant juvenile life stage of individua ls present from this fossil locality. The C. megalodon and associated marine invertebra te and vertebrate faunas from th e late Miocene Gatun Formation of Panama presents the typical characteristics of a shark nursery area: a shallow, productive environment that contains juveniles and neonates. I therefore pr opose the Miocene Gatun Formation, as a nursery area that offered juvenile C. megalodon protection from larger predators and ample food resources (i.e. fishes). This study represents the first definitive eviden ce of an ancient shark nursery area from the Neotropics. Sharks are a very su ccessful group that ha s been common in our oceans for at least 400 million years (Hubbell 1996). This research pres ents evidence that sharks have used nursery areas since ancient times, i.e., for at least 10 m illion years, and therefore extends the record of this behavior and adaptive strategy based on fossil evidence. Nursery areas are critical habitats for the success of extant shark species (Heithaus 2007) Currently, several sharks populations

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75 have declined due to human impact (Myers & Worm 2003; Myers et al. 2007). In planning adequate conservation strategies for sharks, it is important to understand the particular habitats, including those not typical for adults, that are e ssential to the maintenan ce of their populations. Figure 3-1. Temporal comparisons of similar faunas. Comparisons of Carcharocles megalodon tooth measurements (CH: crown height, CW : crown width), in millimeters) from the Gatun Formation (late Miocene), with is olated teeth from a younger (Bone Valley, early Pliocene) and an older formation (C alvert, middle Miocene), which represent three localities form which this species is relatively abundant. Figure 3-2. Life stage comp arisons. Comparisons of Ca rcharocles megalodon tooth measurements (CH: crown height, CW: crow n width) from the Gatun Formation with tooth sets of: a juvenile from the Bone Valley Formation and an adult from the Yorktown Formation. Note the size differen ce in relation with the tooth positions: larger teeth are the most anterior (e.g. A 1, A2, L1, L2) whereas smaller teeth are the most lateral (e.g. L8, L9, l7, l8, l9). For more details on tooth positions, see Appendix C.

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76 Figure 3-3. Total length histogram. Frequency of Carcharocles megalodon individuals at different life stages based on Gottf ried et al [14]. Neonates of C. megalodon reach until 4 m; juveniles until 14 m, and adults more than 17 m.

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77 Table 3-1. Carcharocles megalodon isolated teeth from the Gatun Formation, Panama Specimen CW (mm) CH (mm) Position**Mean TL (m)*** UF 237898 53.0 50.0* A1-A2 5.9 UF 237914 31.4 46.4 L1-L5 8.0 UF 237949 35.7 32.9 A1-A2 3.9 UF 237950 47.7 54.2 a2 7.3 UF 237951 26.8 17.6 L1-L5 3.1 UF 237952 43.2 31.3 L1-L5 5.4 UF 237953 30.9 24.5 l1-l5 7.2 UF 237954 41.7 41.2 A1-A2 4.9 UF 237955 28.4 28.5 A1-A2 3.4 UF 237956 44.9 28.1 l4-l6 16.8 UF 237957 26.7* 19.4 L6-L9 13.8 UF 237959 16.1 16.0 a1-a2 2.2 UF 242801 31.2 27.5* L1-L5, l1-l56.4 UF 242802 45.1 41.0 L1-L5 7.1 UF 242803 40.8 34.7 L1-L5 6.0 AT04-17-1 43.2 43.8 a1-12 6.2 AT04-41-2 60.3 56.4 A1-A2 6.7 AT06-9-1 57.7 60.1 A1-A2 7.1 UF 245844 20.6 11.2 l5-l7 10.0 UF 245852 73.2 70.9* L2-L4 10.8 UF 245885 39.6 36.6 L1-L3 5.2 UF 245886 45.6 40.5 L1-L5 7.0 UF 245996 31.8* 25.9 l3-l6 13.1 UF 245995 62.2 63.2 a3 11.0 UF 246002 35.0 24.5 L7-L9 11.5 UF 246003 52.4 45.4 L1-L3 6.4 UF 245925 23.2 19.2* L6-L9 13.7 CTPA 6671 74.7 72.3 A1-A2 8.6 Incomplete specimens. Measurement predicted using the line equation: y=mx+b (see Appendix E). ** Range of possible positions where every tooth could have belonged (see Appendix C for position details). *** Mean TL estimated based on Shimada (2003) (see Appendix H). Mean calculated from the average among the different positions where every tooth could have belonged.

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78 CHAPTER 4 BROADER IMPACT COMPONENT: ENGAGING YOUNG LEARNERS IN SCIENCE THROUGH A W EBSITE ON FOSSIL SHARKS FROM PANAMA Introduction After the above studies on the ancient sharks of the Neotropics, one m ay wonder: why is this subject important? As scie ntist, we know that understanding the past can help us to comprehend the present and predict the future. We also know that science knowledge seeks to improve human life in fundamental ways; e.g. de veloping treatment for diseases, technologies for distributing clean water in arid environm ents, building systems for enhancing national security and building computers models that help track the impact of human behavior on the environment (Michaels et al. 2008). What we do not necessarily know quite well as scientists is how to convey scientific knowledge to the general public, and part icularly children, nor how to create appropriate opportunities to engage young learners in the scientific enterprise. But why is it important to engage young l earners in science? Generating scientific productivity requires the workforce not only of scientist, but also journalists, teachers, politicians, and the broader network of people who ma ke critical contributions to science. It is essential to engage children to science, not only because they will be the scientists, journalists, teachers and politicians of the futu re; but also because science is a critical factor in maintaining and improving the quality of life; we live in a sc ientific and technological driven society and its population will need to be f unctionally literate in scie nce (Michaels et al. 2008). Engaging young learners in auth entic science allows the development of a foundation for continued science learning. Young learners who learn to communicate with their peers in a scientific way (following logical connections among ideas, and ev idencing and criticizing them) may use these skills in other professional fiel ds (Michaels et al. 2008) Science learning also provides children the opportunity to think critically, giving th em tools to become functional

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79 members of society rather than mere observers. In summary, science is a resource of becoming better citizens. Problem Even when som etimes, scientists do not know how to engage young learners to science; parents, teachers and the genera l population do not either. Someti mes, the media do not send the right message to young learners. In television (the grea test source of information for children), the image of a scientist is often the mad scientis t, neglected, reclusive, and in a white lab coat (usually a white male), whose job is to invent things without applic ation. Other times, the scientist is a wicked man, whose discoveries or inventions are evil for humanity (Massarini 1999). That is a negative view of scie nce and is not engaging at all. As an example of the disengagement to knowledge, statistics from the UNESCO reveal that in Panama for instance, about 98% of ch ildren receive primary education. However, only 65% continue their secondary education; 45% of young people continue to higher education and of these, less than 8% have level of expert ise or PhD (UNESCO. Institute for statistics 2009). Today, the Internet has become a growing a nd powerful communication medium that provides new opportunities as a teaching tool for the citizens of the future. Objective The objective of this work is to develop a kid-friendly and bilingual website about fossil sharks from Panama hosted by the STRI kids webpage, to engage young learners to science learning. This website will promote scie nce and technology and young learners will: Learn what species of sharks existed in Pa nama before the formation of the Isthmus 4 million years ago, Learn about the present and futu re of extant shark species. Learn concepts on biology, eco logy, geology and paleontology.

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80 Background Learning is more than th e tr ansfer of knowledge from teacher to student in a formal learning environment. It is also a social proc ess that includes on diffe rent individuals with different experiences and social environmen ts (Vygotsky 1978). Beyond the schools, there are several opportunities for learning informally. Each year, tens of millions of Americans of all ages, explore and learn about sc ience by visiting informal learni ng institutions, participating in programs, and using media to pursue their interests (NRC, 2009). The purpose of informal science education programs is to help the public to improve their understanding of science and to promote lifelong learning. But, does people actually learn science on informal settings? The Committee on Learning Science in Informal Environments of the US National Academic Council (NRC) concluded that in everyday experiences, designed settings, and programs, individuals of all ages learn science. Today, popular media, in the form of radio, televi sion and the Internet, make science information gradually more available to people across venue s for science learning. These media are shaping peoples relationship with science and are prov iding new means of supporting science learning. Unlike the formal programs (in classrooms), in formal programs focused on a much broader and diverse audience (different ag e ranges, ethnicities, scientific training, etc.), (Wheaton and Ash 2008). This is why it is very important to recognize the richness and complexity of the audience before designing a program of info rmal education as a website. For instance, preconceptions (prior learning that can act as barrier to learning) needs to be known given that it will significantly shape how they make sense of what they are taught. Preconceptions are a powerful support of for further leaning and if they are not addressed properly, they will memorize the content rather th an understand it (NRC, 2000).

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81 Studies in learning theory (Screven 1990) have indicated that audience interviews during front-end evaluation before beginning the design of an informal program will generate essential information to guide the development of the prog ram. For instance, is important to evaluate audiences knowledge, which is what visito rs consciously know, and their engagement, excitement and involvement in science (Friedman 2008). Moreover, other research has shown that the us e of two languages in informal education is very useful for students to access science (W heaton and Ash 2008). In the case of Panama, bilingual schools teach sc ience in English, while some young learners speak Spanish at home. Conversely, other schools teach classes in Span ish and young learners learn science in their native language; however, these young learners also need to learn a second language. In the case of young learners learning science in Englis h, bilingual education programs provide them informal opportunities to join their knowledge in both languages and thus improve their vocabulary; in the case of young learners learning science in Spanish, they can also learn vocabulary and reinforce and/or learn English. Young elementary school children reason bi ologically, rather than exclusively psychologically (Evans et al. 2009). Studies have shown th at even the youngest have sophisticated ways of thinking about the na tural world: Based on experience with the environment and in their pursuit of understa nd the world around them ; children develop scientific ideas. Moreover, young learners who attend informal education programs (online or traditional) are more predisposed to form scientific skills (Michaels et al. 2008). The Internet offers a new way to teach scie nce so that young learners can learn both science ideas and skills. The in teractivity of Web 2.0 technologie s allows children to create, share and edit scientific content as well as to comment about it. Contrary to the static textbooks

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82 that teach science in a linear fashion, with the Internet, scientific concepts can be communicated in a dynamic and creative way, which is closer to how science really works. This turns out to be more attractive and less intimidating for both stud ents and teachers and does not ignore fun (Sanders 2009). The findings from current research of the impor tance of the Internet in supporting informal learning have resulted in recommendations to create quality online experiences (Soren 2004, Soren and Network 2005, Alwi, A and McKa, E. 2009) for both adults and children of all ages. The recommendations include for example, to share information, learn through experience, explore databases, exchange ideas, offer signifi cant content, and use friendly formats that facilitate comparisons with different learning styles. With the advent of Web 2.0, the Internet is more than pages with information young learners read. It provides child ren the opportunities to become We b-creators; they publish their thoughts, respond to others, post pictures, share f iles, and contribute to the content available online, that is, they are part of the Read/Wr ite Web and they have fun doing so. Young learners are building vast social networks with no adult guidance, and teachers and parents on the other hand, have been slow in to adapt to thes e new tools and potentials (Richardson 2009). There are a growing number of Web 2.0 tools that young learners are using every day that have great potential for science education. In this project, diffe rent Web 2.0 tools are used to integrate children to the content of the website. They are among others (Richardson 2009): Social Networks: Web spaces where people can connect with friends and friends of their friends [e.g. www.facebook.com and www.twitter.com ]. Online photo galleries: Web-based communities were photo graphers share their photos, ideas and experiences [e.g. www.flickr.com ]. Blogs: It is an easily created, easily updateab le, Websites that allows authors to publish instantly to the Internet, like a journal [e.g. www.blogger.com ].

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83 Wikis: It is a collaborative Web space wh ere anyone can add or edit content [e.g. www.wikipedia.com ]. Podcasts: S ites where people can easily produce and publish audio and videos [e.g. www.youtube.com ]. Fossil Sharks from Panama as a Science-Engaging Tool Why Fossil Sharks? In the geologic record, shark teeth are th e m ost abundant vertebrate fossils present worldwide (Hubbell 1996) and today they fascinate collectors, scientists, and the general public. Evaluations of audience preferen ces in museums have revealed that fossil sharks are very attractive for young learners as well (MacFadden 2006) (Figure 4-1) Fossil shark teeth permit the understanding of the composition of ancient faunas as well as the environmental conditions that helps to comprehend the climate changes that have occurred in earths history. Thus the history of fossil sharks allows understanding numerous im portant STEM areas of natural sciences such as biology, ecology, geology and paleontology. Fossil sharks causes young learners curiosity and in turn leads to education in the sciences. Why Panama? The Isthm us of Panama was completely formed in the Pliocene (~ 4 Ma) (Cronin et al. 1996) separating the Caribbean Sea and Pacific Ocean. Before this event, the two seas converged in the region forming the Central America Seaw ay (Collins 1996). The abundant fossil record in this area indicates that before the formation of the isthmus, during the Miocene, numerous shark species inhabited the area (Gille tte 1984, Pimiento et al. 2009). For this Masters research, and in collaborat ion with STRI and the FLMNH we collected approximately 400 new fossil shark teeth specimens from the Miocene Gatun Formation of Panama. Over the past 20 years, the Gatun Formation localities ha ve been extensively used to

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84 extract sediment for construction and we predict that these outcrops will soon likely be excavated completely. We therefore capit alized on this current opportunity before these fossils are no longer available for collection in the field. This large collection has a great potential to be used not only with scientific proposes, but also, as a teaching tool for young learners. Panama nian young learners would be more appealing to learn about fossil sharks from Panama. This is what is called placed-based learning; an educational philosophy that promotes learning that is rooted in what is local. One of the strengths of this type of education is that it can adapt to the exclusive characteristics of particular places and in this way, it helps to overc ome the disjuncture between school and real life (Smith G. A. 2002). Given the fact that a large percentage of young learners from Panama are bilingual, the science-engaging product should be bilingual as we ll, and therefore, more attractive for a broader audience around the world, which is a great advantage. English is the most used language in the Internet with 478 million users, and Spanish the third most used with 138 million users. Another advantage of Panama is the collaboration with STRI (Smithsonian Tropical Research Institute). STRI is a bureau of the Smithsonian Institution based in Panama, dedicated to understanding biological dive rsity. The institute not only of fers unique opportunities for longterm ecological studies in the tropics, but also different informal educational programs, including Punta Culebra. Punta Culebra Marine Center is a hands-on and open-air museum for kids that is focused mainly on marine science, education, conser vation and interpretation of marine coastal environments. More than 700,000 students and vi sitors have visited Punta Culebra since it opened in 1996, and hundreds of schools have taken part in its educational program.

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85 The Marine Center is a place where indi viduals can increase their awareness and appreciation of coastal and ma rine environments in Panama and nearby regions of South and Central America. Its goal is to increase public understanding of Panama s past and present coastal environments, promoting their conservati on. It is also meant to show how scientific discoveries improve our understanding and deep ens our appreciation of the natural world [ http://www.stri.org/english/visit_us/culebra/ ]. STRI also offers an engaging W ebsite, in cluding a site specially for young learners [ www.stri.org/kids ] where kids can learn about th e Panam anian biodiversity by doing experiments and playing games. Front-End Evaluation: Learning from and about the Audience Research indicates that in developing inform al learning exp eriences, front-end evaluations can provide important informati on about the learners knowledge and also gauge the programs development. Young learners from 3 to 15 years old were randomly chosen from two bilingual schools in Panama City (Figure 4-2): The Isa ac Rabin and The Balboa Academy. In each school and were involved in focus groups interviews. In each school, principals asked parents for permission to have their students involved. Af ter they received parent al consent, around 10 groups of 4-6 learners answered a survey (Appe ndix B); their answers we re archived with a voice recorder. All questions inquired to investigate the stat e of knowledge on the i ssues intended to be addressed in the Website, what they would like to know, their misconceptions, how to make the Website attractive to them and th e group of ages the Website should be addressed to. It should be noted, however, that information was not used to conduct statistical analyses in a research. The data from these surveys was used to improve the design and learning go als of the Website and are described as follows:

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86 Young learners want to learn, by using: Short text A lot of photos and figures A lot of videos Fun fonts for texts Brilliant colors Accurate and specific information (to the point) A character (avatar) that can guide young learners throughout the site. Other linked resources, for example, Wikipedia and National Geographic What they already know: What a fossil shark Fossil sharks teeth look darker than living sharks teeth What is a fossil shark Sharks are marine animals Sharks live in the sea Extinction is the end of a species Dinosaurs became extinct 65 Ma Megalodon is an ancient shark Fossil shark teeth have different co lors as opposed to living sharks Shark skeletons are composed of cartilage Scientist know about ancient species because they can find their fossils What they want to kn ow about fossil sharks: How long did a shark lived? Different shark tooth morphologies How many fossil sharks are found in Panama? Are extant sharks in danger? What do sharks eat? What did Megalodon eat? Ancient sharks sizes Do sharks eat people? How did fossil sharks loose their teeth? How big was Megalodon? Who was the first shark? How old is the first shark? Where did Megalodon live? Where do fossil sharks come from?

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87 Misconceptions: Sharks eat people Sharks eat only meat Geologic time goes to trillion years Evolution=improvement Humans are responsible for Megalodon extinction Dinosaurs appeared before sharks Fossil sharks go extinct Fossil means in the time of dinosaurs Fossils are 1000-3000 years old Evolution=Evolution of humans Sharks have infinite number of teeth Fossil shark teeth are 10 years old Fossils shark teeth are from living organisms Fossils shark teeth are no older than 90 years old Websites young learners visit: Youtube Facebook Wikipedia Google National Geographic Grades range: Young learners are more interested in fossil shark teeth from 2nd grade to 6th grade. Kindergarteners and 1st graders did not show too much interest. Even when older kids (from 6th to 9th grade) were interested on the subject, they were not on learning on a Website for especially made for kids. Based on this findi ng, in this study, the ta rget audience is young learners from 2nd to 6th grade. Title for the website: The title young learners like the most was: Fossil Sharks from Panama Website Design Formative Evaluation After the focus groups survey, I designed the f our m ain sections in paper. STRI graphic designer (Ricardo Chong) prepared all graphs, while STRI Webmaster (Marisol Lopez) put all

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88 the material together in a digita l offline format. This first draft was then shown to a group of 6th graders after a class field trip to one of Gatun Formations localities, where they collected and identified several fossil shark specimens. The young learners pointed out the main issues they considered could be a problem when using the We bsite (Figure 4-3). Some of these issues were difficulties to find some of sections and lack of guidance while navigating on the Website. Particular attention was made to their reaction when finding two languages in each text; young learners found it advantageous for their lear ning. Negative issues we re addressed and the Website was developed [ http://stri.org/e nglish/kids/sharks/ ]. Web 2.0 Facebook: T he Website is connected to Facebook throughout a page called Fossil Sharks of Panama with information and news about th e fossil sharks and news about the Website in general. In this page, young learners also can post anything they want, including thoughts, videos, photos, songs, notes, etc. Young learners can become fans of this page; then other young learners see that in the newsfeed of their frie nds, and become fans as well, thus increasing the number of participants accessi ng the Website. Therefore, the Fo ssil Sharks of Panama Facebook page is also a way to promote the Webs ite. This page is completely bilingual. Blog: The Website has its own Blog hosted by Google. In this Blog, news about the site is posted, and young learners can respond to it with ideas, recommendations and com plaints. They can also start a new subject to be discussed. Th e name of the Blog is: Fossil Sharks of Panama and is completely bilingual. Wiki: The Website is linked to a Wiki hosted by W ikispaces. This is a tool were young learners can add or edit informa tion that is also found in the Webs ite. The idea is to have little information in the Wiki so young learners can complete it using the Website as a source of information. This Wiki called sharkspanama is a al so great tool to be use in formal educational

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89 settings (i.e. can be used as a fun assignment for kids to comple te at home, for group project or as classroom activity). The Wiki have some pages in English and others in Spanish. Youtube: Several videos are part of the W ebsite content. All these videos are downloadable via Youtube. Flickr: Several im ages are part of the Website c ontent. All these figures and pictures are posted in Flickr where young learners can comment about them and also share them with their friends. Flickr is therefore a tool to promote the Website. Website Sections Every W ebsite section covers different subjec ts on fossil sharks from Panama. However, all sections have common design elements, including: a cartoon (avatar) who will guide young learners while navigating on the Web; key wo rds linked to Wikipedia; a self-assessment questionnaire where the target audience will test wh at they have learned, and also, questions that encourage them to do more research; links with more information and finally, video-interviews to experts in each subject. The content of each section was chosen based on the front-end survey. Geologic time The objectiv e of the section is the target audien ce to realize the magn itude of the geologic time and recognize major evolutionary events so they can properly place in temporal context the rest of the content of the Website. This was select ed as the first section because the majority of misconceptions were related with this issue. In this section, young learners will learn about the different forms of life that exist in the fossil record through the geologic time from the earliest forms that appear in the Cambrian, to the more complex forms (i.e. humans) that first appear during the Quaternary. Young learners will lear n the dimension of the geologic time by comparing it with a virtual trip through the Pa nama Canal (Figure 4-4), where every number in

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90 the tour represents a period; by clicking on every nu mber, images of the forms of life that appear in these periods will be displayed. Fossil sharks In this section, the target a udience will learn about the shar ks species inhabited Panam a when it was covered by water before the formation of the isthmus. The section is divided into 2 main parts. The first is an introductory section where the target audience learns about fossils in general (i.e. what they are, how they form a nd how they are found) (Figure 4-5A). The second section is more like a cyber-exhibit where young lear ners some fossil sharks taxa that have been discovered in the Gatun Formation from Panama (Figure 4-5B). Here, young learners will learn about their teeth morphology, maximum total length a nd diet. In addition to this, this section has a picture of a tooth of every species, a picture of th e shark if it is an extinct species, or a video of the animal if it is an extant species (Figure 4-5C). Megalodon This section is about the biggest sharks that have ever lived: Megalodon ( Cacharocles megalodon). The study of this species was a very im portant research component of this thesis. Furthermore, the front-end evaluation indicated that it is also the specie s that kids are more interested. In this section young lear ners will learn the most importa nt facts about this fascinating creature and will clarify some misconceptions that young learners and general public may have regarding this species. The content of this section will answer the following questions: How big was it? When did it live? How long did it live? What did it eat? What did it do in Panama? Why did it become extinct ? and Why is it important? (Figure 4-6). Present and future The objective of this section is to bring young learners back to the present and look outside the box to the f uture. Here the target audience will learn important facts about living

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91 sharks in general, but also, they will be able to realize how threatened shar ks are currently due to the harmful activities of humans. An additional a nd also most important objective of this section is to clarify that sharks are not man-eaters. The content of this section will answer the following questions: What is a shark? What is the origin of sharks? Where do sharks live? How do they reproduce? What do they eat? Ar e they dangerous to humans? and Are humans dangerous to sharks? (Figure 4-7). Recommendations and Best Practices In this p roject, I built a Website specially ma de for young learners. In the process, I learned a lot about this new way to communicate scie nce, especially about 4 main issues: Communication with the Team As recomm ended by Soren (2004), the constant communication with every member of the team, helped to the appropriate development of th e Website. It is important for every member to be in the same line of thinking, so the different parts of the Webs ite are showed in a integrated way, and not like if every person had a different ve rsion of how the website should be. To avoid this, regular meetings were held at different stages of the de velopment of the Website. During these meetings we discussed our ideas and each time a product was completed, team members were engaged in reviewed before moving to the next phase. Keep it Simple For the developm ent of the Website, the simple we kept the design, the better. When doing the front-end and formative evaluations, I notic ed that young learners appreciated when the format was kept simple, rather than too sophistic ated. For example, when just one click reveals the question they want to an swer, rather than a whole path of different clicks.

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92 Short Texts Keeping the texts short, was a quite a challe nge. From the evaluations I learned that young learners would not read more than a paragraph and that they w ould prefer looking at the graphs and other pictorial presentations. In order to give them all the information in one paragraph or less, I limited that information to what I learne d during the front-end eval uation about what they actually wanted to know about fossil sharks. When extra information was pertinent, the Website provided two types of links: one with more info rmation about that topic in the segment More info of every section, and other to Wikipedia wh en I considered they needed a definition of certain word. Evaluations Mean Everything To know the audiences preferen ces was essential for the devel opm ent of this website. The interviews to young learners gave us beneficial information (such as what questions they have about sharks, what they already know, how they wa nt to website to be, etc). This information was used to shape the design and content of th e site. Without this information, I would do a completely different version of the site such for example; I would focus more on morphology of the fossil teeth. We simply do not know what young learners want, we simply cannot think as a young learner, therefore the information needed will have to be elicited from using such methods as focus groups interviews The Future of the Website The objective of this section of m y master thesis was to pres ent the process If developing a fun, kid-friendly and bilingual Website on fossil sharks from Panama. My goal was to achive the broader educational impact of an activity that integrates the res earch and educational content of my thesis. However, this project as an outre ach activity will continue to foster young learners curiosity and provide co ntinued information.

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93 Even when the website will be self-promote d throughout the different social networking applications, other plans for continuity will include a dissemination campaign to be conducted via presentations to teachers, students and parents from different schools in Panama so they can know about the site and also how to use it. A teac hers guide will be prepared with the help of middle-school educators so they can use the Website as part of their curriculum. I will also give talks about this project at prof essional scientific, educational, and /or museum meetings. And finally, press releases in di fferent newspaper will be done to promote this activity. The website will be permanently displayed in th e Culebra Nature Center. Here a panel is devoted to fossils from Panama and young learners play as paleontologist s, digging out fossils and then identifying them. In the case of fossil shark teeth, they use the Website to identify the species the found and to answer guided questions which at the same time a great venue for further research. Summative evaluations after young learners use the Website w ill be conducted to reflect and evaluate the successes of the Websites for online users. Based on the findings of these evaluations, I am planning to write a manuscript to be published in a specialized journal. In addition, user statistics, feedback messages a nd blog, wiki, and networking activity will be a Website assessment. In addition, it will likely be necessary to update content, building different generations of sections, connect the Website with the Web 2.0 app lications of the future, and to offer different levels of design to ensure that users keep coming back to the Website

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94 A. B. C. Figure 4-1. Young learners find collecting fossil sh arks a fascinating subject. Families and school groups often go to collect fossil sharks teet h at Las Lomas, a well-known locality in the Gatun Formation. A. Three 4th grade learners from the Balboa Academy find a fossil shark tooth. B. Two 4th grade girls also from the Balboa Academy look for fossil sharks. C. A young enthusiast finds a shark tooth wh en looking for fossils with his family.

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95 A. B. C. Figure 4-2. A-C. Young learners from the Is aac Rabin School answered a survey after they observed a fossil shark tooth. They were allowed to take the tooth home.

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96 Figure 4-3. Formative evaluation: A dr aft of the Website was showed to 6th grade young learners form the Balboa Academy. The children pointed out the main issues they considered could be a problem when using the Website. Figure 4-4. Geologic Time. A virtua l trip thru the Panama Canal, as an analogy of the geologic time. Every number represents a period, where 1 is the Cambrian and 11 is the Quaternary period. By clicking on every numbe r, images of the forms of life that appear in these periods will be displayed ( http://stri.org/englis h/kids/sharks/tiempo.ht ml).

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97 A. B. C. Figure 4-5. Fossils. A. In this se ction young learners learn what is a fossil, how they are formed and how can they be found. B. Some of the 16 taxa that were identified in the Gatun formation during this research. C. Informa tion about every species: time range, tooth morphology, maximum total length and diet ( http://stri.org/english/kids/shark s/acerca_fosiles.html ).

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98 A. B. C. D. E. F. G. Figure 4-6. Megalodon. A. Size. B. Time Range. C. Longevity. D. Diet. E. Nursery Area in Panama. F. Extinction. G. Importance ( http://stri.org/english/ki ds/sharks/megalodon_intro.htm l ).

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99 A. B. D. C. F. E. G. Figure 4-7. Sharks Present and Future. A. Defi nition. B. Origin. C. Re production. D. Diet. E. Habitats. F. Danger to humans. G. Threats ( http://stri.org/english/kids/sharks/presFut_intro.htm l ).

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100 CHAPTER 5 GENERAL CONCLUSIONS This study contributes to the understanding of the an cient selachian biod iversity during the late Miocene of Pana ma, expanding our knowledge of the ichthyofauna of the Gatun Formation. Our field discoveries, further analysis of ex isting collections and ta xonomic identifications, indicate that the sharks from this unit consist of a relative diverse assembla ge of at least 16 taxa, including four species that are extinct today. The remaining portion of the total selachian biodiversity has taxonomic affinities with modern taxa, and indicate relativ ely long-lived species. These taxa demonstrate stasis for several million years and at least their tooth morphology re mains similar to extant individuals. They survived the formation of the Isthmus of Panama as opposed to several other species of that became extinct due to the effects of this event. Based on the known habitat preferences for modern selachians analog assemblages, the Gatun sharks were primarily adapted to shallow waters (i.e., between about 20 to 40 m depth) within the neritic zone. This paleodepth asse ssment is also consistent with previous interpretations based on the extensive marine invertebrate fauna from the Gatun Formation. Furthermore, in comparison with modern species, we infer that the Gatun shark fauna has mixed Pacific-Atlantic (Caribbean) biogeographic affi nities due to its centr al location between two ancient ocean basins. However, one species ( Carcharhinus perezi ) became restricted to the Caribbean Sea after the Isthmus closed. The comparisons of Gatun dental measurements with older and younger formations containing similar biodiversity suggest that ma ny of the species have an abundance of small individuals. This discovery is very interesting because based on ex tant species, juvenile sharks

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101 use shallow environments as nursery areas similar to those interpreted to have existed in the late Miocene Gatun Formation. Although not very common, one of the species present in the Gatun Formation, Carcharocles megalodon has surprisingly small fossil teeth. This extinct shark was the biggest shark that ever lived. In th is study I carefully studied C. megalodon dentition found in the Gatun Formation and calculated the total length of all C. megalodon individuals based on their crown height to estimate the life stage based on overall body size. These results confirm that the C. megalodon individuals from Gatun were mostly juveniles and neonates, with estimated body lengths between 2 and 14 meters. I therefore pr opose the Gatun Formation as a paleo-nursery area for young C. megalodon. Previous paleo-nursery areas proposed for this species were mostly anecdotal and based on the presence of juvenile foss il teeth accompanied by fossil marine mammals. However, none of these were subjected to rigorous analyses. In cont rast, the life stage of Gatuns individuals was not only inferred based on their body lengths in th is study, but also the t ooth sizes from this formation was compared with those found in older and younger formations to determine if the small size observed is unique to th e species during the late Miocene. I found that there is no tende ncy for increased size in C. megalodon over time, and that the small size observed in the Gatun Formation is ther efore not related to micr oevolutionary shifts in body size or with the tooth position within the jaw. Finally I conclude that C. megalodon from the Gatun Formation fed on the abundant fishes o ccurring in this shallow environment and that the small size observed is not due to a scarcity of large prey items. The results obtained in this research, along w ith previous knowledge of the paleoecology of the Gatun Formation (a shallow-water productiv e marine environment) demonstrate that the

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102 Gatun Formation was used as a nurse ry area during the late Miocene by C. megalodon, and consequently show that sharks have used nursery areas for millions of years as an adaptive strategy during their life histories; extending the timing of this behavior based on the fossil record. For this Masters research, and in collaborati on with STRI and the FLMNH we collected a total of approximately 400 new fossil shark teet h specimens from the Miocene Gatun Formation of Panama. This large collection has the great potential to be used not only for scientific research, but also as a teaching tool for young le arners. Evaluations of audience preferences in museums have revealed that fossil sharks ar e very attractive for young learners. Additionally, fossil shark teeth permit the understanding of the composition of ancient faunas as well as the environmental conditions that helps the public to comprehend the climate changes that have occurred during earth history, and therefore allows understanding numerous important STEM concepts of natural sciences. In addition to the scientific research conducte d during this master project, a broader impact deliverable was produced. A kid-fr iendly and bilingual website about fossil sharks from Panama: Fossil sharks from Panama [ http://stri.org/english/kids/sharks/ ], was developed with a target audience of young learners to engage them to scie nce. The site was designed to create a quality online experience based on evaluations to differe nt-aged young learners and following the best practices. The website incorporates differe nt Web 2.0 applications, as well as four main sections that covers different subjects on fossil sharks fr om Panama. All sections have common design elements, including: a cartoon (a vatar) who guides young learners while navigating on the Web, key words linked to Wikipedia, a self-assessment questionnaire, links with more information and

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103 finally, video-interviews with experts in each su bject. In the different sections, young learners learn about: (1) geologic time, (2) major evolutio nary events, (3) general concepts about fossils, (4) ancient sharks that inhabited Panama befo re the formation of the isthmus (teeth morphology description, total length of the animal and diet), (5) important facts about Megalodon (what it ate, how big was it, how long did it liv ed, why did become extinct, etc. ), and (6) living sharks (what is shark, what do they eat, how they reproduce, etc.). In summary, this masters research contri butes to the unde rstanding of the systematics, paleobiology, and paleoecology of late Miocen e sharks from panama and integrates an educational component, conveying scientific knowledge to the gene ral public, and particularly children, hopefully engaging them in science learning.

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104 APPENDIX A CHAPTER 2 TOOTH DIAGNOSTIC CHARAC TERS AND DIMENSIONS A Tooth diagnostic characters as these pertain to the fossil shar ks described in this study. B. Tooth measurement codes and dimensions.

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105 APPENDIX B CHAPTER 2 DATA Extant shark species occurring in Isthm us of Panama. Indicat es species also present in the Gatun Formation fossil record. Species Common name Distribution Alopias pelagicus Pelagic thresher Pacific Alopias superciliosus Bigeye thresher Caribbean/Pacific Alopias vulpinus Thresher shark Caribbean/Pacific Carcharhinus acronotus Blacknose shark Caribbean Carcharhinus albimarginatus Silvertip shark Pacific Carcharhinus altimus Bignose shark Caribbean Carcharhinus falciformis* Silky shark Caribbean/Pacific Carcharhinus galapagensis Galapagos shark Pacific Carcharhinus leucas* Bull shark Pacific/Caribbean Carcharhinus limbatus Blacktip shark Pacific and Caribbean Carcharhinus longimanus Oceanic whitetip shark Pacific and Caribbean Carcharhinus obscurus* Dusky shark Pacific/Caribbean Carcharhinus perezi* Caribbean reef shark Caribbean Carcharhinus porosus Smalltail shark Caribbean/Pacific Carcharhinus plumbeus* Sandbar shark Caribbean/Pacific Carcharias taurus Sand tiger shark Caribbean Carcharodon carcharias Great white shark Caribbean/Pacific Galeocerdo cuvier* Tiger shark Pacific/Caribbean Ginglymostoma cirratum Nurse shark Pacific/Caribbean Heptranchias perlo Sharpnose sevengill shark Caribbean/Pacific Heterodontus mexicanus Mexican hornshark Pacific Heterodontus quoyi Galapagos bullhead shark Pacific Isurus oxyrinchus Shortfin mako Caribbean/Pacific Mustelus canis Smooth dogfish Caribbean Mustelus dorsalis Sharptooth smooth-hound Pacific Mustelus minicanis Houndshark Caribbean Mustelus norrisi Narrowfin smooth-hound Caribbean Mustelus lunulatus Brown smooth-hound Pacific Nasolamia velox Whitenose shark Pacific Negaprion brevirostris* Lemon shark Pacific/Caribbean

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106 Appendix B Continued. Species Common name Distribution Odontaspis ferox Smalltooth sand tiger Caribbean/Paific Prionace glauca Blue shark Caribbean/Pacific Pseudocarcharias kamoharai Crocodile shark Caribbean/Pacific Rhincodon typus Whale shark Caribbean/Pacific Rhizoprionodon lalandei Brazilian sharpnose shark Caribbean Rhizoprionodon longurio Pacific sharpnose shark Pacific Rhizoprionodon porosus Caribbean sharpnose shark Caribbean Rhizoprionodon terraenovae Atlantic sharpnose shark Caribbean Sphyrna mokarran* Great hammerhead Caribbean/Pacific Sphyrna tiburo Bonnethead Caribbean/Pacific Sphyrna tudes Smalleye hammerhead Caribbean/Pacific Sphyrna zygaena Smooth hammerhead Caribbean/Pacific Sphyrna corona Scalloped bonnethead shark Pacific Sphyrna lewini* Scalloped hammerhead shark Caribbean/Pacific Sphyrna media Scoophead shark Caribbean and Pacific Triaenodon obesus Whitetip reef shark Pacific

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107 APPENDIX C CHAPTER 3 REPRESENTATION OF A CARCHAROCLES MEGALODON DENTITION Tooth size and shape varies greatly within the ja w. Left side, adapted from Gottfried et al. (1996).

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108 APPENDIX D CHAPTER 3 CARCHAROCLES M EGALODON COLLECTION FROM THE GATUN FORMATION The 28 Carcharocles megalodon specimens colle cted with its collection number. CTPA 6671 was not available to photograph.

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109 APPENDIX E CHAPTER 3 LINE REGRESSIONS FOR TOOTH MEASUREMENTS. A. Known CW. Line regression calculated when is possible to measure the CW (i.e. CW in the x or independent axes) but the CH is unknown due to fossil preservation. B. Known CH. Line regression calculated when is possible to m easure the CH (i.e. CH in the x or independent axes) but the CH is unknown due to fossil preservation.

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110 APPENDIX F CHAPTER 3 MEASUREMENTS FROM BONE VALLEY FORMATION C archarocles megalodon isolated teeth m easurements, fr om the Bone Valley Formation, Florida, USA. Specimen CW (mm) CH (mm) UF 217225 69.8 67.3 UF 300 70.7 73.7 UF 234583 79.8 81.1 UF 217140 78.7 75.2 UF 209170 59.8 55.8 UF 228480 56.5 50.6 UF 17850 53.4 49.4 UF 17980 44.0 47.0 UF 17850 48.9 46.1 UF 228479 46.1 42.8 UF 209164 46.4 40.7 UF 17839 37.2 32.5 UF 17839 33.7 30.8 UF 24715 46.4 45.9 UF 24715 41.4 44.6 UF 24715 43.1 41.3 UF 24715 38.4 38.2 UF 24715 33.2 35.6 UF 24715 43.7 31.9 UF 17872 54.0 45.8 UF 17872 44.9 38.3 UF 17872 40.0 31.4 UF 17872 36.2 33.6 UF 17872 46.2 36.1 UF 17872 34.1 35.4 UF 17872 31.9 20.8 UF 17872 25.8 24.6 UF 17872 26.6 23.4 UF 17872 31.5 31.7 UF 55973 38.7 35.2 UF 55973 35.1 29.6 UF 17840 46.9 42.1 UF 17840 33.2 27.0

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111 Appendix F Continued. Specimen CW (mm) CH (mm) UF 17840 40.3 35.0 UF 17840 21.8 16.6 UF 132595 33.3 35.2 UF 132588 31.7 29.4 UF 132593 30.3 33.4 UF 229807 33.4 33.7 UF 229804 29.9 20.8

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112 APPENDIX G CHAPTER 3 MEASUREMENTS FR OM THE CALVERT FORMATI ON Carcharocles megalodon isolated teeth, from the Calvert Formation, Maryland, USA. Specimen CW (mm) CH (mm) USNM 457364 32.2 26.9 DJB 2152 55.8 36.0 USNM 494369 44.4 45.0 USNM 489141 55.5 47.1 USNM 475347 52.3 48.8 USNM unnumbered 67.7 63.9 USNM 489136 86.8 68.1 USNM 494370 102.6 71.8 DJB 1029 27.1 26.6 DJB 1566 29.4 26.2 USNM 489137 43.9 45.6 DJB 850 57.3 55.5 DJB 1860 64.5 52.7 DJB 1933 62.2 79.9 DJB 1766 36.8 34.6 DJB 1061 36.0 29.8 DJB 1564 35.6 33.9 ACC NO. 418873 30.1 19.8 ACC NO. 413905 43.6 35.6 DJB 1975 59.8 55.6 DJB 934 26.9 21.4 DJB 2009 25.0 17.5 R.O. 411148 32.3 21.3 USNM unnumbered 47.1 33.5 USNM 475303 34.4 38.1 USNM 475306 39.8 30.5 USNM 475299 30.4 33.0 USNM unnumbered 23.7 24.8 USNM 475304 30.7 36.8 USNM 473302 31.3 30.2 USNM 475290 30.6 27.4 USNM475297 34.0 19.3 DJB 2090 67.8 68.8 USNM4 95294 39.5 38.1 PAL 535357 32.1 27.6

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113 Appendix G Continued. Specimen CW (mm) CH (mm) USNM 26189 36.3 39.8 USNM 171153 59.7 47.6 USNM 171156 73.8 50.8 USNM 24956 23.8 22.1 USNM 24956 61.2 52.7 USNM 171182 35.9 31.3 USNM 337208 39.1 26.4 USNM 171170 22.3 14.8

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114 APPENDIX H CHAPTER 3 MEASUREMENTS JUVENILE TOOTH SET Juvenile Carcharocles megalodon associated tooth set, from the Bone Valley Form ation, Florida, USA. Position* CW (mm) CH (mm) A1 82.7 82.3 A2 78.8 75.4 A3 76.7 80.2 L1 77.6 79.2 L2 77.5 87.8 L3 73.7 81.6 L4 68.2 71.7 L5 53.7 62.2 L6 36.3 50.6 L7 32.2 48.2 L8 19.9 34.1 L9 14.2 21.0 a1 68.7 59.8 a2 72.0 67.9 a3 74.0 64.7 l1 67.2 63.0 l2 67.7 66.8 l3 63.1 65.8 l4 55.8 63.9 l5 46.7 58.8 l6 34.4 48.4 l7 21.3 32.8 l8 10.8 22.2 For position details, see Appendix C

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115 APPENDIX I CHAPTER 3 MEASUREMENTS ADULT TOOTH SET Adult Carcharocles megalodon associated tooth set, from the Yorktown Formation, North Carolina, USA. Position* CW (mm) CH (mm) A1 107.3 104.6 A2 105.6 102.2 A3 103.5 99.3 L1 114.3 100.2 L2 112.3 97.8 L3 110.4 98.3 L4 109.0 95.7 L5 109.5 85.6 L6 89.7 64.6 L7 63.7 37.5 L8 56.8 28.3 L9 40.9 14.8 a1 84.5 81.8 a2 96.7 85.5 a3 95.0 91.0 l1 96.2 88.0 l2 90.5 83.6 l3 89.6 81.0 l4 90.0 75.5 l5 79.8 59.3 l6 62.3 39.0 l7 49.3 31.1 l8 39.3 15.6 For position details, see Appendix C.

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116 APPENDIX J CHAPTER 3 TOTAL LENGTH Total length regres sion based on CH of every tooth position, Shimada (2003). Position Regression Equation (x=CH) A1 TL= 5.234+11.522x A2 TL= -2.16+12.103x A3 TL= 19.162+15.738x L1 TL= 5.54+14.197x L2 TL= 4.911+13.433x L3 TL= 0.464+14.550x L4 TL= 5.569+17.658x L5 TL= -5.778+26.381x L6 TL= -71.915+50.205x L7 TL= -8.216+14.895x L8 TL= -7.643+13.597x L9 TL= -10.765+17.616x a1 TL= -8.216+14.895x a2 TL= -7.643+13.597x a3 TL= -10.765+17.616x l1 TL= 9.962+17.437x l2 TL= 1.131+19.204x l3 TL= -30.947+25.132x l4 TL= -51.765+35.210x l5 TL= -73.120+55.262x l6 TL= -117.456+96.971x l7 TL= -64.732+138.350x l8 TL= -137.583+231.411x

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117 APENDIX K CHAPTER 4 FOCUS GROUP SURVEY Objectives 1. To identify what they know about fossil sharks and m isconceptions. 2. To know what misconceptions and knowledge do they have regarding concepts such as biodiversity, extinction, e volution, conservation and th e nature of science. 3. To realize what to the want to know about fossil sharks 4. To find out the appealing features of the website that will cause they to enter. 5. To receive additional unanticipated (open-ended) feedback from the children as a result of the focus group brainstorming. Assent ScriptParent or Guardian of Minor My nam e is [insert interviewers name] and I am conducting a survey about web site on fossil sharks that Im planning to develop for the summer of 2009. Can I ask you some questions? This survey should take about 5 minutes to complete. All questi ons are answered anonymously. You do not have to answer any questions that y ou do not wish to answer. This is a voluntary survey, so you may withdraw from it at any time without consequences. Procedure Receive parental approv al Select various groups of 3-5 kids from different ages. Record the ages and grade. Give them a fossil shark tooth. Ask: 1. What is it? If dont know, explain it is a fossil shark teeth [O1] 2. What is a shark? [O1] 3. Where do they live? [O1] 4. What do sharks eat? [O1] 5. What is a fossil shark? [O1] 6. How old do you think are these teeth? [O1] 7. What comes to your mind when you hear the world evolution? [O2] 8. What came first dinosaurs, sharks or humans? [O2] 9. Why do scientists say that some sharks are in danger of extinction? [O2] 10. How scientists know that? [O2]

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118 11. What do you like to know about fossil sharks? [O3] 12. What you think is cool about fossil sharks? [O3, O4, O5also elsewhere] 13. Where do you learn about fossil sharks? In the web? [O4] 14. What web sites do you visit? Why? [O4, O5] 15. I am developing a kids web site on foss il sharkswhat do you think I should have on it? 16. What should it be called? [04]

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119 LIST OF REFERENCES Adnet, S., P O. Antoine, S. R. H. Baqri, J. Y. Crochet, L. Marivaux, J. L. Welcomme, and G. Metais. 2007. New tropical car charhinids (chondrichthyes, Ca rcharhiniformes) from the late Eocene-early Oligocene of Baluchistan, Pakistan: Paleoenvironmental and paleogeographic implications. Journal of Asian Earth Sciences, 30:303-323. Agassiz, L. 1833-1843. Recherches sur les poisons fossils. Neuchatel, Vol. 3, 390 p. Aguilera, O., and D. R. De Aguilera. 1996. Ba thymetric distribution of Miocene and Pliocene Caribbean teleostean fishes from the coast of Panama and Costa Rica. Pp. 251-270 in L. S. Collins and A. G. Coates, eds. A Paleobiotic Survey of Caribbean Faunas from the Neogene of the Isthmus of Panama. Bulletin 357, Pale ontological Research Institute, Ithaca, New York. Aguilera, O., and D. R. De Aguilera. 2001. An exceptional coastal upwelling fish assemblage in the Caribbean Neogene. Jour nal of Paleontology, 75:732-742. Aguilera, O., and D. R. De Aguilera. 2004. Gi ant-toothed white sharks and wide-toothed mako (Lamnidae) from the Venezuela Neogene: Thei r role in the Caribbean, shallow-water fish assemblage. Caribbean Journal of Science, 40:368-382. Alejo-Plata, C., J. L. Gomez-Ma rquez, S. Ramos, and E. Herr era. 2007. Presence of neonates and juvenile scalloped hammerhead sharks Sphyrna lewini (Griffith and Smith, 1834) and silky sharks Carcharhinus falciformis (Muller and Henle, 1839) in the Oaxaca coast, Mexico. Revista De Biologa Marina y Oceanografa, 42:403-413. Ameghino, F. 1906. Les formations sdimentai res du Crtac suprieur et du Tertiare de Patagonie avec un parallle entre leurs faune s mammalogiques et celles de lancien continent. Anales del Museo Naci onal de Buenos Aires, 3(15)8:1-508. Applegate, S. P. 1974. A revision of the higher taxa of Orectoloboids. Journal of the Marine Biological Association of India, 14:743-751. Applegate, S. P. and L. Espinosa-Arr ubarrena. 1996. The fossil history of Carcharodon and its possible ancestor, Cretolamna : a study in tooth id entification. Pp 19-36 in A. Klimley and D. Ainley, eds. Great Wh ite Sharks: the Biology of Carcharodon carcharias Academic Press, San Diego, California. Alwi, A., and E. McKay. 2009. Investigating online museum exhibits and personal cognitive learning preferences. Proceed ings ascilite Auckland 2009. Berg, L. S. 1958. System der rezenten und fossile n Fischartigen und Fische. Deutsche Verlag Wissenschaften, Berlin, Germany, 310 p. Blainville, H. M. D. 1816. Prodr ome dune nouvelle distribution sy stematique de regne animal. Bulletin de Sciences de la Socit Philomatique de Paris, Pt. 8:113-124.

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120 Blake, S. F. 1862. Fossil shark teeth at Panama. The geologist, 5: 316. Bonaparte, C. L. 1838. Selac horum tabula analytica. Nuovi Annali delle Scienze Naturali, Bologna, Ser. 1(2):195-214. Borne, P. F., T. M. Cronin, and J. E. Hazel. 1996. Neogene-Quaternary Ostracoda and paleoenvironments of the Limon Basin, Costa Rica, and Bocas del Toro Basin, Panama. Pp. 231-250 in L. S. Collins and A. G. Coates, eds. A Paleobiotic Survey of Caribbean Faunas from the Neogene of the Isthmus of Pana ma. Bulletin 357, Paleontological Research Institute, Ithaca, New York. Budd. A. F., K. G. Johnson and T. A. Stemann. 1996. Plio-Pleistocene Turnover and Extinction in the Caribbean Reef-Coral Fauna. Pp. 168-204 in J. B. C. Jackson, A. F. Budd, and A. G. Coates, eds. Evolution and environment in tropi cal America, University of Chicago Press, Chicago. Bush, A. and K. Holland. 2002. Food limitation in a nursery area: estimates of daily ration in juvenile scalloped hammerheads, Sphyrna lewi ni (Griffith and Smith, 1834) in Kane'ohe Bay, O'ahu, Hawai'i. Journal Experimental Marine Biology and Ecology, 278: 157-178. Cappetta, H. 1980. Modification du Satut Generique de queleques especes de slaciens crtacs et tertiares. Palae overtebrata, 10:29-42. Cappetta, H. 1987. Chondrichthyes II : Mesozoic and Cenozoic Elasmobranchii. G. Fischer Verlag, Stuttgart; New York, 193 p. Casier, E. 1960. Note sur la collection des poi ssons paleochnes et iochnes de l'Enclave de (Congo). Annales Museum Roya l Congo Belge (A.30) 1, 2:1-28. Castro, J. I. 1993. The shark nursery of Bulls ba y, South Carolina, with a review of the shark nurseries of the southeastern coast of the United States. Environmental Biology of Fishes, 38:37-48. Cione, A., J. A. Mennucci, F. Santalucita, C. Acosta Hospitaleche. 2007. Local extinction of sharks of genus Carcharias Rafinesque, 1810 (Elasmobranchii, Odontaspididae) in the eastern Pacific Ocean. Revista geologica de chile, 34:139-145. Coates, A. G. 1996a. Lithostratigraphy of the Ne ogene strata of the Caribbean coast from Limon, Costa Rica, to Colon, Panama. Pp. 17-38 in L. S. Collins and A. G. Coates, eds. A Paleobiotic Survey of Caribbean Faunas from the Neogene of the Isthmus of Panama. Bulletin 357, Paleontological Resear ch Institute, Ithaca, New York. Coates, A. G. 1996b. Appendix B Stratigraphic S ections. Pp. 299-348 in L. S. Collins and A. G. Coates, eds. A Paleobiotic Survey of Caribbean Faunas from the Neogene of the Isthmus of Panama. Bulletin 357, Paleontological Res earch Institute, Ithaca, New York.

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121 Coates, A. G., J. B. C. Jackson, L. S. Collins, T. M. Cronin, H. J. Dowsett, L. M. Bybell, P. Jung, and J. A. Obando. 1992. Closure of the Isthmus of Panama: The near-shore marine record of Costa Rica and western Panama. Geologica l Society of America Bulletin, 104:814-828. Coates, A. G., and J. A. Obando. 1996. The geologic evolution of the Central American Isthmus. Pp. 21-56 in J. B. C. Jackson, A. F. Budd, and A. G. Coates, eds. Evolution and environment in tropical America, Univ ersity of Chicago Press, Chicago. Cocke, J. 2002. Fossil shark teeth of the worl d: A collector's guide, Lamna Books, Torrance, California, 150 p. Collins, L. S. 1996. The Miocene to Recent dive rsity of Caribbean benthic foraminifera from the Central America Isthmus. Pp. 91-108 in L. S. Collins and A. G. Coates eds. A Paleobiotic Survey of Caribbean Faunas from the Neogene of the Isthmus of Panama. Bulletin 357, Paleontological Resear ch Institute, Ithaca, New York. Collins, L. S., A. G. Coates, W. A. Berggren, M. P. Aubry, and J. J. Zhang. 1996. The late Miocene Panama isthmian strait. Geology, 24:687-690. Compagno, L. J. V. 1977. Phylet ic relationships of living sharks and rays. American Zoologist, 17:303-322. Compagno, L. J. V. 1984. FAO species catalogue. Vol. 4. Sharks of the world. An annotated and illustrated catalogue of shark species known to date. Part 2. Carcharhiniformes. FAO Fisheries Synopsis, Pp. 251-655. Compagno, L. J. V. 1988. Sharks of the order Carcharhiniformes, Princeton University Press, Princeton, New Jersey, 486 p. Cronin, T. M. and H. J. Dowsett. 1996. Bio tic and oceanographic response to the Pliocene closing of the Central American Isthmus. Pp. 76-104 in J. B. C. Jackson, A. F. Budd, and A. G. Coates, eds. Evolution and environment in tropical America, University of Chicago Press, Chicago. Daimeries, A. 1889. Notes ichthyologiques. V. A nnales de la Societe Royale Malacologique de Belgique, Tome XXIV. Bull. de Seances p. XL Voir aussi, Bruxelles. De Muizon, C., and T. J. Devries. 1985. Ge ology and paleontology of late Cenozoic marine deposits in the Sacaco area (Peru). Geologische Rundschau, 74:547-563. Dos Reis, M. A. F. 2005. Chondrichthyan fa una from the Pirabas Formation, Miocene of northern Brazil, with comments on paleobiogeography. Anuri o do Instituto de Geociencias, 28:31-58. Donovan, S. K., and G. C. Gunter. 2001. Fossil shar ks from Jamaica. Bulletin of the Mizunami Fossil Museum, 28:211-215.

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122 Donovan, S. K., R. K. Pickerill, R. W. Portell, T. A. Jackson and D. A. T. Harper. 2003. The Miocene palaeobathymetry and palaeoenvironm ents of Carriacou, the Grenadines, Lesser Antilles. Lethaia, 36:255-272. Duque-Caro, E. 1990. Neogene stratigraphy paleoceanography and paleobiogeography in northwest South America and the evolution of the Panama seaway. Palaeogeography, Palaeoclimatology, Palaeoecology, 4:203-234. Ebert, D. A. 2002. Ontogenetic changes in the diet of the sevengill shark ( Notorynchus cepedianus) Marine Freshwater Research, 53:517-523. Ehret, D. J., H. Hubbell, and B. J. MacFadden. 2009. Exceptional preservation of the white shark Carcharodon (Lamniformes, Lamnidae) from the early Pliocene of Peru. Journal of Vertebrate Paleontology, 29:1-13. Estrada, J. A., A. N. Rice, L. J. Natanson, and G. B. Skomal. 2006. Use of isotopic analysis of vertebrae in reconstructing ontogenetic feeding ecology in white sharks. Ecology, 87:829834. Evans, E. M., A. N. Spiegel., W. Gram, B. N. Frazier, M. Tare, S. Thompson, and J. Diamond. 2009. A Conceptual Guide to Natural Hist ory Museum Visitors Understanding of Evolution. Journal of Research in Science Teaching Advance Online Publication. DOI 10.1002/tea.20337 18 November 2009. Frazzetta, T. H. 1988. The mechanics of cutting and the form of shark teeth (Chondrichthyes, Elasmobranchii). Zoomorphology, 108:93-107. Friedman, A. (Ed.). 2008. Framework for Evaluating Impacts of Informal Science Education Projects. Washington D.C.: National Science Foundation. 117 p. Garla, R. C., D. D. Chapman, M. S. Shivji, B. M. Wetherbee, and A. F. Amorim. 2006. Habitat of juvenile Caribbean reef sharks, Carcharhinus perezi at two oceanic insular marine protected areas in the southwes tern Atlantic Ocean: Fernando de Noronha Archipelago and Atol das Rocas, Brazil. Fi sheries Research, 81:236-241. Gibbes, R. W. 1848-1849. Monograph of the fossil Squalidae of the United States. Journal of the Academy of Natural Sciences of Philadelphia, Ser. 2, Pt. 1:139-206. Gill, T. 1872. Arrangement of the families of fi shes, or Classes Pisces, Marsupiobranchii, and Leptocardii. Smithsonian Mi scellaneous Collections, 230:1-49. Gillette, D. D. 1984. A marine ichthyofauna fr om the Miocene of Panama, and the Tertiary Caribbean faunal province. Journal of Vertebrate Paleontology, 4:172-186. Glckman, L. S. 1964. Sharks of the Paleogene and their stratigraphi c significance. Nauka Press, Moscow, 229 p. (In Russian).

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131 BIOGRAPHICAL SKETCH Catalina Pimiento is a Colombian biologist. She has worked with sharks since 2002; first in Mexico, where she did her undergraduate th esis on the population ecology of the whale sharks that occur in th e Contoy National Park in the Mexican Caribbean. For the last 5 years, Catalina has worked in Panama at the Smithsonian Tropical Research Institute, where she first worked at the Naos Marine Laboratory studding the migration patterns of whale sharks in Las Perlas Archipelago and the Central Pacific Ocean; and then at the Center for Archeology and Paleoecology (CTPA) as a labo ratory assistant. Catalina is currently a biology graduate student at the University of Florida with a minor in Science Education. She works as a researcher-curator of Florida Muse um of Natural History. Her current research has two main components, in one she studies the paleoecology of fossil sharks from Panama and in the other component, she develops Internet tools to engage children to science. After attending her first paleontol ogy meeting, the Discovery Channel News Website published a report about her research on the nursery area for the Megalodon in the Miocene of Panama. After she finishes her master, Catalina is looking forward to keep working not only on sharks paleoecology, evolution, biodiversity, development, migrations routes, and conservation; but also on the deliveri ng scientific information to children.