Building the Canal: Earth Science and Paleontology

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Building the Canal: Earth Science and Paleontology
Series Title:
Science Lesson Plans and Teacher Resources for Panama and Canal-related Stereographs
Grant, Claudia ( Author, Primary )
Hoffman, Robert ( Author, Primary )
Madden, Jill ( Author, Primary )
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Level 3 - a course, or set of lesson plans
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Interactivity Level:
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Subjects / Keywords:
Fossils ( lcsh )
Panama Canal (Panama) ( lcsh )
Panama Canal (Panama)--Construction. ( lcsh )
Forest biodiversity ( lcsh )
Engineering ( lcsh )
Paleontology ( lcsh )
Hydraulic engineering ( lcsh )
Science ( lcsh )
lesson plan ( aat )
serial ( sobekcm )
Spatial Coverage:
Panama -- Central America -- Panama Canal Zone
9.1110858 x -79.6993185


This set of lesson plans and teacher resources is intended to teach a variety of scientific concepts to students in grades 6-8. The lessons are related to the Panama Canal, including expansion, fossil excavation work, and history. The lesson plans can be used individually or as a larger set.

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University of Florida
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Panama Canal Museum Collection at the University of Florida
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Copyright Claudia Grant, Robert Hoffman, and Jill Madden. Permission granted to University of Florida to digitize and display this item for non-profit research and educational purposes. Any reuse of this item in excess of fair use or other copyright exemptions requires permission of the copyright holder.

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Panama and the Canal
University of Florida


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*denotes a required field *Lesson Title : Building the Canal Earth Science and Paleontology PREZI Presentations Introduction: L1A Building the Canal: Earth Science & Paleontology Extension: L1B Geological Timescale *Lesson Summ ary : This lesson will uncover the story of the evolution of life on earth as it is told through the geological time scale. The lesson will use specific examples of fossils found at the Panama Canal as evidence for the story. *Subjec t : Earth Science *Intended Audience/Grade Level: Middle School (6 8) *Time Frame : A. Prior Knowledge Piece ( approx. 15 min) B. Academic Language ( approx. 50 min. ) C. Reciprocal Team Work ( approx. 110 min. or 1 block period) D. Interactive Lecture (approx. 50 min. ) E. Peer Review Reflection (approx. 50 min. ) Standards and Purpose *Standards (link appropriate Common Core State Standards, Next Generation Sunshine State Standards, or other standards below ): MS ESS1 4. Construct a scientific explanation based on evidence from rock strata for how the g eologic time scale is used to organize Earths 4.6billion year old history. [Clarification Statement: Emphasis is on how analyses of rock formations and the fossils they contain are used to establish relative ages of major events in Earths history. Examples of Earths major events could range from being very recent (such as the l ast Ice Age or the earliest fossils of homo sapiens) to very old (such as the formation of Earth or the earliest evidence of life). Examples can include the formation of mountain chains and ocean basins,


*denotes a required field the evolution or extinction of particular living org anisms, or significant volcanic eruptions.] [Assessment Boundary: Assessment does not include recalling the names of specific periods or epochs and events within them.] MS ESS2 2. Construct an explanation based on evidence for how geoscience processes have changed Earths surface at varying time and spatial scales. [Clarification Statement: Emphasis is on how processes change Earths surface at time and spatial scales that can be large (such as slow plate motions or the uplift of large mountain ranges ) or small (such as rapid landslides or microscopic geochemical reactions), and how many geoscience processes (such as earthquakes, volcanoes, and meteor impacts) usually behave gradually but are punctuated by catastrophic events. Examples of geoscience pr ocesses include surface weathering and deposition by the movements of water, ice, and wind. Emphasis is on geoscience processes that shape local geographic features, where appropriate.] MS ESS2 3. Analyze and interpret data on the distribution of fossils and rocks, continental shapes, and seafloor structures to provide evidence of the past plate motions. [Clarification Statement: Examples of data include similarities of rock and fossil types on different continents, the shapes of the continents (including continental shelves), and the locations of ocean structures (such as ridges, fracture zones, and trenches).] [Assessment Boundary: Paleomagnetic anomalies in oceanic and continental crust are not assessed.] *UFDC Resources : www.ufdc.u OTHER RESOURCES 11415945 Guiding Question(s) : 1. What is the geological timescale and what does it tells us about the evolution of life on Earth? 2. What stories can be told from discovering remains of dead organisms? (What are fossils and how do scientists use them to better understan d the past?) *Objective s : 1. Identification and explanation of key academic science language used in the context of doing fossil research. 2. Doing scientific research from a textbook to understand what a fossil is and how scientists use them.


*denotes a required field A. Prior Knowledge Piece B. Academic Language C. Reciprocal Team Work D. Interactive Lecture E. Peer Review Reflection 3. Taking Cornell Notes 4. Reading a chart on the geological timescale. 5. Working in research teams doing cooperative work. Assessment (how will data be collected on student performance?) *Formative: Peer Review Reflection The peer review ref lection will be inserted toward the middle of the lessons activities at the discretion of the teacher as a way for the students to explore their meaning making of the content with their peers. It will allow the teacher to evaluate the student's construction of the new information. *Summative: Students will answer the following focus questions at the end of the lesson activities to demonstrate their understanding of the content. What is the geological timescale and what does it tell us about the evolution of life on Earth? What stories can be told about the changing ecosystems on our planet from discovering the remains of ancient organisms? How are the fossils found at the Panama Canal important to our understanding of the evolution of life on earth? Teaching Phase ( See attachments section ) *Activate/Build Prior knowledge: A. Prior Knowledge Piece *Direct Instruction: B. Academic Language : W orking in research teams students will review textbook pages 264 269, L ooking at Fossils and will scan the text for key science words critical to the understanding of the fossil content. They will identify 8 words and complete the vocabulary illustrated dictionary packet for their words. C. Reciprocal Team Work: T his activity has been designed to give students skills in extracting science information from grade level text and to record that information as Cornell Notes. The


*denotes a required field students will be coached in the process of Reciprocal Teamwork, the clarification of key academic language, and Cornell note taking. Each research team will work cooperatively to res earch content from textbook pages 264 269, Looking at Fossils. *Guided Practice: B. Academic Language C. Reciprocal Team Work D. Interactive Lecture *Independent Practice (reinforce the concepts and skills developed in the lesson) : Coloring pages of the Interactive Lecture *Closure : Refer to summative assessment Reading strategies: Reading with the purpose to complete the Cornell notes using a textbook. Writing strategies: Peer review reflections Speaking and listening strategie s: Reciprocal teamwork *Accommodations Special needs will be accommodated in a case by case situation based on the school policy and resources. Each lesson is designed to present the material through the different learning modalities (visual, auditory, kinesthetic). *Extensions Re Teaching: Teacher can expand on the importance of the Panama Canal expansion. This PREZI shows more images of the initial excavation of the canal, the main cuts where fossils have been found and closeup of fossil images. L1B Geological Timescale n=share&utm_medium=copy&rc=ex0share Enrichment: Who s on First, a Relative Dating Acti vity: SETA Lesson Plan: History of Life on Earth nt/d/18vnv4eu5X8EWXpdUMgtYGKDdjxlodV


*denotes a required field VgL2 9VDRGQ68/preview by Jason Borgen Google Certified Teache r *Materials Special materials/ preparation needed : Text book pages Worksheets Coloring pencils Suggested technology: Internet access to visit PREZI presentations Teacher Reflection (Questions to stimulate reflection on the process of teaching) Teacher learning: How did my students respond? What would I do differently next time? What would I keep the same? How will I use primary sources in the future? Attachments A. Prior Knowledge Piece Working as a science team students will fill out this T chart to record and share their prior knowledge. The left side is to be filled out by each individual student. The right side is to be filled out as the team shares what they knew with each other. This will be followed by a c lass share out which is recorded by the teacher on a wall chart.


*denotes a required field Fossils & Geological Time This is What I Know! This is What My Team Members Know!


*denotes a required field B. Academic Language Science Vocabulary: Name Those Hard Words! The Word I Know it Well: I could teach it to my team! I have Seen it or Heard it Before: I recognize it, but I need a r eview I dont Know What it Means Adapted from: Lenski, Susan. Reading and Learning Strategies from Middle and High School Students, pg. 38. The Language of Science! Complete each section for each of the words your team has selected for studying our unit. Science Word Explain the best meaning of the word. Illustrate the meaning of your word.


*denotes a required field C. Reciprocal Team Work Select a teacher: The teacher supports the team, selects who reads the text, takes all notes, & writes the summary statement for each segment of the research. Make a Prediction: Each team member reviews the text to be researched and is asked by the teacher to share their prediction of what they feel the text will be about. The teacher asks each team member to give the reasons for their predicti ons. Predictions are only made at the beginning of the session. Read the Piece of Selected Text: The teacher selects who will read the section of text being researched to the team. All other team members read along. Clarification: The teacher asks for words or ideas that the team would like clarified. At least 3 words must be clarified for each segment of text. The team works together to clarify the material. The teacher records it and all team members copy it on the back of their Cornell Notes. Cornell Notes and Questions: The teacher guides the teams to record at least 4 Cornell Notes and a corresponding Cornell Question for each segment of text. The teacher records this and the each team member copies it. Summary Statement: The teacher will write one sentence that best summarizes the main point of the text segment and each team member copies it. Cornell Notes Example Front of each page: Looking at Fossils Cornell Questions Cornell Notes How do fossils form? Fossils are formed from the hard parts of an organism in sedimentary rock. What happens if the body part of an organism does not decay? Fossils only form if the body doesnt decay. What are the best body parts to be fossilized? Body parts that are hard like shells, teeth, and bones; they are the easiest to preserve as fossils. Please note that the notes are written first and then the students write a question that has the note as its answer. Summary Statement: Fossils are the preserved body parts of organisms that are found in sedimentary rock if the hard parts of the body do not decay. (Pg. 264) Back of each page: Clarifying 1. Sediment: dirt, mud, sand found at the bottom of a body of water (ocean, pond, river).


*denotes a required field 2. Preserved: to keep the remains of an organism so that they stay in the shape they were. 3. Decay: when an organism dies and its body rots or decomposes. D. Interactive Learner See handouts below: Interactive_Lecture01, Interactive_Lecture02, and Interactive_Lecture03. E. Peer Review Reflection How to Write a Peer Review Reflection Writing your reflection: Date your reflection. Copy the title and the prompt for your reflection. Answer the prompt sharing your thoughts and ideas in at least 7 well written sentences. How to respond to a peer Read your peer's reflection. Write a sentence about something you found interesting in their reflection. Write a sentence telling them new information. Ask a science question that connects to the topic of the prompt. Sign your name and return the reflection to your peer. Title: The Geological Timescale and the Evolution of Life on Earth Prompt: Please describe how the fossil record is used by scientists to understand how the Earth's environments and the organisms that lived in them have changed over time.


EON ERA PERIOD/ SUBPERIOD EPOCH Age estimated in million years before present unless otherwise noted Phanerozoic Cenozoic (C z ) Quaternary (Q) Holocene Pleistocene Tertiary (T) Neogene (N) Pliocene Miocene Paleogene (P ) Oligocene Eocene Paleocene Mesozoic (Mz) Cretaceous (K) Jurassic (J) Triassic ( T R ) Paleozoic (P z ) Permian (P) Carboniferous (C) Pennsylvanian (IP) Mississippian (M) Devonian (D) Silurian (S) Ordovician (O) Cambrian (C) EON ERA PERIOD Age estimated in million years before present Proterozoic (P) Neoproterozoic (Z) Ediacaran Cryogenian Tonian Mesoproterozoic (Y) Stenian Ectasian Calymmian Paleoproterozoic (X) Statherian Orosirian Rhyacian Siderian Archean (A) Neoarchean Mesoarchean Paleoarchean Eoarchean Hadean ( p A) U.S. Department of the Interior U.S. Geological Survey 1ASKUSGS Ages shown for divisions of geologic time are general representations. For more specific age information, see U.S. Geological Survey Fact Sheet 2010. GIP 141 11,700 yr 2.588 5.332 23.03 33.9 55.8 65.5 145.5 199.6 251.0 299.0 318.1 359.2 416.0 443.7 488.3 542.0 635 850 1000 1200 1400 1600 1800 2050 2300 2500 2800 3200 3600 4000 4600 Continued on other side


KEY TO THE FOSSIL SHARKS OF THE GATUN FORMATION CLAVE PARA IDENTIFICAR TIBURONES FSILES DE LA FORMACIN GATUN MEGATOOTHED MEGADIENTES EXTINCT CARCHARHINIDS CARCHARHINIDOS EXTINTOSExtinct Tiger Shark Physogaleus contortus Snaggletoothed Shark Hemipristis serra EXTANT CARCHARHINIDS CARCHARHINIDOS ACTUALES Tiger Shark Galeocerdo cuvier Lemon Shark Negaprion brevisrostris Hammerhead Shark Sphyrna sp. Dusky Shark Carcharhinus obscurus Bull Shark Carcharhinus leucas Caribbean Reef Shark Carcharhinus perezi Upper Lower Megalodon Carcharocles megalodon RAY PLATES PLACAS DE RAYAS


56 SCIENCE SCOPE from and about the pastby Catalina Pimiento and Rose M. PringleHave you ever felt the excitement of school-aged children as they observe fossils in a museum? Children are usually enthusiastic to learn about prehistoric remains or fossils of both plants and animals. Recent studies on preferences in museums have revealed that children are fascinated by fossil sharksthe remains of sharks that inhabited the oceans of the past (MacFadden 2006). This has created new opportunities to connect informal science learning at museums to public school science curricula. By studying fossil sharks, children learn about the composition of ancient faunas and the geologic changes that have occurred in the Earths history. A study of fossil sharks can be tied to numerous important areas of natural (Earth) sciences such as geology, geography, and paleontology. Studies of fossil sharks can also be connected to science, technology, engineering, and mathematics (STEM) topics, such as evidence for evolution and climate change in the past. In this article, we describe a series of science activities for middle school students that focuses on the study of fossil sharks through an examination of the morphological characteristics of their teeth by using models, drawings, and websites. The activities presented are intended to guide students toward an understanding of timescales and fossils as providing important evidence of how life and environmental conditions have changed over time. The activities are presented in three sections. In the rst section, students will learn general concepts of fossils and identify fossil-shark species based on the morphological characteristics of their teeth. In this section, students will conclude that fossil sharks can be found on land, even though sharks are marine animals. Experiences in Section 2 will allow students to discover for themselves that the Earth is dynamic and continents are in constant dynamic movement. This will help students to understand how it is possible to nd the remains of sharks on land. Finally, in the last section, students will explore the dimension of geologic time and will integrate the knowledge and skills learned in the rst two sections. Sample of fossil shark teeth collected in Panama and Florida FIGURE 1 FLORIDA MUSEUM OF NATURAL HISTORY/SMITHSONIAN TROPICAL RESEARCH INSTITUTE SCIENCE SAMPLER


57 February 2011 BackgroundFossil shark teeth Sharks belong to the group of animals called vertebrates, animals with backbones and spinal (vertebral) columns. However, sharks are cartilaginous, which means their skeletons are made of cartilage rather than bones. Because they lack bones, teeth are the only shark remains hard enough to be preserved, and they are the most commonly found remains of vertebrates in the fossil record. Oftentimes, sharks fossils are found on land, indicating that in the past, that particular area was covered with water. Plate tectonicsScientic evidence indicates that the positions of continents have changed over geologic time as a result of plate tectonics. These Earth movements have resulted in the continents drifting apart and the formation of new landmasses. In support of this concept, scientists have cited similarities between fossils and living organisms found in North America and Europe and in South America and Africa.Geologic timeGeologic time is the framework for deciphering the history of our planet (Ogg, Ogg, and Gradstein 2008). The geologic timescale describes the timing of events occurring over the course of the history of the Earth by organizing the most important events in units such as epochs, eras, and periods, where every unit is related to certain fossils.Fossils tell important stories about plate tectonics. Related fossils are often discovered at varied geographic locations, demonstrating the dynamic nature of the continents. In this section, students will learn general concepts of fossils and why remains of marine organisms are often found on land. This learning task is supported by an engaging, student-friendly website about fossil sharks. In addition, students will work like paleontologists and identify fossil-shark species based on the morphological characteristics of shark teeth.MaterialsPictures of fossil shark teeth (Figure 1) Table to record observations (Figure 2) A geologic timescale featuring some of the major events in Earths history (Figure 3) Student questions (Figure 4) World map ( moll.jpg) Fossil shark website ( kids/sharks)Part 1: Shark teethHave students observe the pictures in Figure 1 (do not tell them they are shark teeth) and record the features of each specimen in Figure 2. Allow students to locate along the geologic timescale (Figure 3) the period of existence of each specimen (tooth) and its geographic location on a world map. Conduct a discussion on the identifying features listed in Figure 2 and establish that the pictures in Figure 1 are fossil shark teeth. Have students explore the fossil-shark website sections Fossils and Teeth and answer the questions in Figure 4. Students could be Features of the specimens What are these specimens? How did you come to this conclusion? observations of the species in Figure 1 FIGURE 2 SCIENCE SAMPLER


58 SCIENCE SCOPE paired to conduct this reading-comprehension activity, and responses can be elicited in a wholegroup discussion. In classrooms with limited availability of computers, a single computer and a projector can be used to engage a group of students or the whole class in exploring the website.Part 2: Students as paleontologistsWhen paleontologists identify shark species based on fossil teeth, they usually compare the teeths morphology (i.e., shape, color, structure, conguration, pattern, and size) with a catalog of previously identied teeth. A catalog could be an identication key or a collection housed in a museum. In this case, an online catalog is provided at dientes.html. In this part, students will use the catalog on the website to identify shark species based on the fossil teeth. The pictures in the catalog are clear and self-explanatory, thus affording ease of identication. Furthermore, the specimens from Figure 1 are very distinctive and unique for each organism. Clicking on each tooth on the website displays additional information about the species. If few computers are available, teachers can download the pictures and accompanying information from the website. These can be formatted into information cards and available as resources in the classroom. Ask students to observe the teeth in Figure 1 and make comparisons with the images from the website. Encourage students to consider their data on the features and differences they recorded in Figure 2, as well as the information provided on the website. Different claims may arisestudents may think that tooth c (tiger shark) is a longtooth tiger shark because of the similarities. Conduct a class discussion and have students articulate their reasoning for each of the responses. Encourage reexamination of the data if necessary, and through negotiation and consensus establish the following identications: (a) megalodon; (b) snaggletooth shark; (c) tiger shark; (d) hammerhead shark; (e) lemon shark. When the teeth have been identied, pose the following question to students: Where do sharks live? The expected answers are water, oceans, and Geologic timescale showing some of the major events in Earths history FIGURE 3 SCIENCE SAMPLER


59 February 2011 the sea. Using the maps and the locations where the shark teeth were found, encourage students to articulate possible questions they now have about the teeth, sharks, or where sharks live. Continue the whole-class discussion guided by either of the following questions: If sharks live in water, why were the shark teeth found on land? Why were these fossils found on land if sharks are aquatic animals? Elicit students responses before moving on to Section 2. Students can learn about the biggest sharks that ever lived (megalodon) and also about recent sharks by exploring the Present and Future sections of the website. through geologic timeFor centuries, scientists believed that continents were xed in their present positions. Over time, this claim was questioned in the face of new scientic evidence. Alfred Wegener, a German meteorologist and geophysicist, proposed in his book The Origin of Continents and Oceans (rst published in 1915) that all landmasses were originally joined in a single supercontinent named Pangaea (Wegener 1966). Wegener represented this concept of continental movement in a series of maps showing the breakup of Pangaea and the movement of the continents to their present-day locations. Wegener supported his continental-drift theory with a large amount of geologic, paleontologic, and climatologic evidence. However, most geologists refused to accept this idea until the 1960s, when oceanographic research provided convincing evidence that the continents had once been joined together and subsequently separated (Monroe and Wicander 2009). Development of plate-tectonics theoryBased on the early concepts of continental drift by Wegener, the modern theory of plate tectonics has evolved. Geologists now explain the mechanisms of geologic change (dynamism) in relation to at least 10 major plates making up the Earths surface (lithosphere) (Petersen and Rigby 1996). By completing Section 2, students will learn how the Earth has changed over geologic time. They will recognize that the some of the continents we now inhabit were once covered by water, or were positioned differently, supporting the theory that throughout geologic time, Earths continents and oceans have been in motion.Materials6 pictures of the Earth at different periods of time (one picture per student group; i.e., group 1: Earth 90 mya; group 2: Earth 65 mya; group 3: Earth 50 mya; group 4: Earth 35 mya; group 5: Earth 20 mya; and group 6: Earth 5 mya) (http://jan.ucc. (access is free) Question Answer (also found on the website) What is a fossil? Fossils are the remains of ancient plants and animals. Fossils can be shells, teeth, bones, and impressions of plants or animals preserved in the Earths crust. How are fossils formed? For fossilization to occur, the organism is buried in sediment. Then, chemical alterations occur for many years where minerals from the sediment ll empty spaces in the organism (bone, tooth), which cause it to turn to rock and fossilize. How do paleontologists nd fossils? When paleontologists look for fossils, they walk all over the area, looking closely at the ground. If the ground where the organism is buried is eroded, fossils can then be exposed. What are the main features of a shark tooth? Crown, root, edges, cusplets, neck, and heels Student questions for Section 1, with answers provided FIGURE 4 SCIENCE SAMPLER


60 SCIENCE SCOPE the following: (1) Continents have changed their positions or moved over time. (2) In the past, the ocean covered certain areas. Each group will make a presentation to communicate their explanation about the possible transformation the Earth experienced. Allow the class to question the presenting groups conclusions. Conduct a whole-group discussion and establish that the Earth has not been static, and the locations, shape, and orientation of the continents and oceans have changed over time. Show the animation that depicts the motion of the continents over time (see Materials list) and ensure that students note the dynamism of the Earths plates. In addition, reinforce the notion that the movement of the Earth occurs over a long period of time measured in millions of years. Pose the following question to make sure students are ready to move on: How can you explain that the shapes of Africa and South America seem to t together? of geologic timeIn order to understand the past, geologists deal with immense spans of time lines. This magnitude of geologic time can be problematic to the untrained. For children, the time between each birthday can seem like an eternity, while the ages of their grandparents represent the oldest they can imagine. Even for an adult, 10 years seems like a long time. In Section 2, duration of time was measured in millions of years. In this section, students will explore the dimension of geologic time and major evolutionary events such as the enormous time span between the formation of the Earth and the appearance of the major forms of life. An understanding of the magnitude of geologic time will further reinforce the occurrence of the Earths dynamic movements resulting in the drifting of continents explored in Section 2. Time (day)* Event in my day Geologic time (million of years)* Event in life history 8:00 a.m. 4,700 8:30 a.m. 4,600 9:00 a.m. 4,500 9:30 a.m. 4,400*30 minutes in everyday time represents 100 million years in geologic time time with geologic time FIGURE 5World map (from previous section, http://jan.ucc. Materials students need to make a group presentation Animation of the movement of continents ( www. visualizations/es0806/es0806page01.cfm?chapter_ no=visualization) (access is free)ProcedureOrganize the class into six groups and distribute to each group a picture of the Earth at different periods of time during the past 100 million years, and a picture of the Earth as it is today. Every group will analyze a different period of time (see Materials list above). Instruct students to explore the picture of the Earth from the past and compare it to one from the present. The following criteria can be used for the comparison: continent size, position, and shape; land area; presence or absence of countries or peninsulas; and distribution of the ocean. A designated group recorder will write down the key points emerging from the groups discussion. Allow students time to discuss among themselves and establish a plausible explanation about how the Earth has changed through time. This explanation should be recorded to be shared in the whole-group discussion that follows. Their explanation may include SCIENCE SAMPLER


61 February 2011 MaterialsA journal for one day Figure 3 Figure 5 Figure 1 ProcedureInstruct students to keep a journal for one day and to every 30 minutes document their activities. Suggest that students title the journal My one day in time. Provide students with Figure 3, a geologic timescale showing the major forms of life. Instruct students to use this gure and their journals to complete Figure 5, a table to compare the activities done in a day with the geologic time, where each 30-minute block of the day is compared with 100 million years in the geologic timescale. Figure 6 shows an example of a sixth-grade students response to Figure 5. Note this typical example where the student clearly notices a large period of time between the formation of the Earth and the rst fossils. In addition, the student records the appearance of humans during the last time interval. By completing this worksheet, students realize the dimension of geologic time. Allow students time (around 20 minutes) to analyze their results and answer the following questions in day time and geologic time (Figure 5): What is the time span between the formation of Earth and the rst appearance of humans? What is the time span between the formation of Earth and the rst shark? How much time is between the rst shark and the rst human? During what period was the last time that the sharks from the previous section (Section 1, Part 2) were able to swim in what it are today Florida and Panama? Worksheet (Figure 5) filled out by a sixth-grade student from the Balboa Academy, Panama FIGURE 6 Discuss students responses and establish that in geologic time, 100 million years are necessary for major events to occur, as opposed to everyday time, where duration of events is about 30 minutes.AssessmentStudents can visit the link sharks/tiempo.html to see a boat crossing the Panama SCIENCE SAMPLER


62 SCIENCE SCOPE Canal. Have students write a journal entry describing their virtual trip through geologic time as indicated on the boat ride. Instruct students to roll the cursor over each of the dots as a guide describing each of the events. With limited computers, you can download each of the pictures and provide the events on a continuum for students to observe and complete the assessment task. Remind students that the fossil record tells us a lot about our past. Ask them to identify two things we can learn from the fossil teeth of sharks and to explain each of their responses.ConclusionThe activities described can serve to introduce students to paleontology, the branch of science that studies the evolution, interactions, and environments of prehistoric organisms. In identifying fundamental concepts and principles that underlie the Earth and space science standard, the National Science Education Standards note that the presence of fossils indicates that many organisms that lived long ago are extinct (NRC 2000). While observing and studying fossils can be exciting to children, understanding the time span and -scale in Earths history can be abstract and requires a cognitive leap on the part of learners. Students involvement in the process as they observe, draw conclusions, and seek supportive data can make a difference in their understanding of abstract concepts that are necessary for further science learning. Acknowledgments This activity was possible thanks to the support of the U.S. National Science Foundation Partnerships in International Research and Education grant 0966884 (OISE, EAR, DRL), EAR 0824299, and EAR 0418042; the Mitchell Hope Scholarship; the Ken Ericson Scholarship; the Autoridad del Canal SCIENCE SAMPLER


63 February 2011 Catalina Pimiento ( is a graduate student in the Department of Biology at the University of Florida/Florida Museum of Natural History in Gainesville, Florida, and the Smithsonian Tropical Research Institute in Panama City, Panama. Rose M. Pringle is an associate professor in the Department of Teaching and Learning at the University of Florida in Gainesville, Florida. de Panama (ACP); the Mark Tupper Fellowship; Ricardo Perez SA; and the National Geographic Society. We also thank the Florida Museum of Natural History, the Smithsonian Tropical Research Institute, the Balboa Academy, B. MacFadden, M. Lopez, R. Chong, C. Jaramillo, L. Oviedo, D. Jones, M. Vallarino, C. Shibuta-Gough, and J. McLaughlin.ReferencesMacFadden, B.J. 2006. Sharks: Predators through time. Front end evaluation. Gainesville, FL: Florida Museum of Natural History. Monroe, J.S., and R. Wicander. 2009. The changing Earth: Exploring geology and evolution. Belmont, CA: Brooks/ Cole, Cengage Learning. National Research Council (NRC). 2000. Inquiry and the national science education standards: A guide for teaching and learning. Washington, DC: National Academies Press. Ogg, J.G., G. Ogg, and F.M. Gradstein. 2008. The concise geologic time scale New York: Cambridge University Press. Petersen M.S., and J.K. Rigby. 1996. Interpreting Earth history: A manual in historical geology. Dubuque, IA: Wm. C. Brown. Wegener, A. 1966. The origin of continents and oceans. Mineola, NY: Dover.ResourcesFossil sharks from Panama Mollewide plate tectonic maps http://jan.ucc.nau edu/~rcb7/mollglobe.html Explore the world of Earth science T oll Fr ee: 888-837-6437www .ver nier .comEnhance LEGO NXT Robotics with Ve rnier SensorsIs your r obotics team looking for deeper investigations and mor e cr eativity? Now you can expand your options beyond the basic sensors included with LEGO Mindstorms NXT Imagine the robotics projects your students could create using a V ernier Magnetic Field Sensor a Force Sensor or a Gas Pressure Sensor The NXT Sensor Adapter can be used with LEGO Mindstorms NXT robots and over 30 Ve r nier sensors for sensor -based control systems.Dozens of robotics videos available at www .ver nier .com/nxt Magnet Finder project: build a robot to detect a magnet hidden under one of three walnut shells. $39ORDER C ODEBT A-NXT SCIENCE SAMPLER


AncientNurseryAreafortheExtinctGiantShark MegalodonfromtheMioceneofPanamaCatalinaPimiento1,2,3* ,DanaJ.Ehret2,4,BruceJ.MacFadden2,5,GordonHubbell61 DepartmentofBiology,UniversityofFlorida,Gainesville,Florida,UnitedStatesofAmerica, 2 DivisionofVertebratePaleontology,FloridaMuseumofNaturalHistory, Gainesville,Florida,UnitedStatesofAmerica, 3 CenterofPaleoecologyandArchaeology,SmithsonianTropicalResearchInstitute,Panama,RepublicofPanama, 4 School ofNaturalResourcesandEnvironment,UniversityofFlorida,Gainesville,Florida,UnitedStatesofAmerica, 5 DivisionofResearchonLearning(DRL),EducationandHuman Resources(EHR),NationalScienceFoundation,Arlington,Virginia,UnitedStatesofAmerica, 6 JawsInternational,Gainesville,Florida,UnitedStatesofAmericaAbstractBackground:Asweknowfrommodernspecies,nurseryareasareessentialsharkhabitatsforvulnerableyoung.Nurseries aretypicallyhighlyproductive,shallow-waterhabitatsthatarecharacterizedbythepresenceofjuvenilesandneonates.It hasbeensuggestedthatintheseareas,sharkscanfindamplefoodresourcesandprotectionfrompredators.Basedonthe fossilrecord,weknowthattheextinct Carcharoclesmegalodon wasthebiggestsharkthateverlived.Previousproposed paleo-nurseryareasforthisspecieswerebasedontheanecdotalpresenceofjuvenilefossilteethaccompaniedbyfossil marinemammals.Wenowpresentthefirstdefinitiveevidenceofancientnurseriesfor C.megalodon fromthelateMiocene ofPanama,about10millionyearsago.Methodology/PrincipalFindings:Wecollectedandmeasuredfossilsharkteethof C.megalodon ,withinthehighly productive,shallowmarineGatunFormationfromtheMioceneofPanama.Surprisingly,andincontrasttootherfossil accumulations,themajorityoftheteethfromGatunareverysmall.HerewecomparethetoothsizesfromtheGatunwith specimensfromdifferent,butanalogouslocalities.Inadditionwecalculatethetotallengthoftheindividualsfoundin Gatun.ThesecomparisonsandestimatessuggestthatthesmallsizeofGatun’s C.megalodon isneitherrelatedtoasmall populationofthisspeciesnorthetoothpositionwithinthejaw.Thus,theindividualsfromGatunweremostlyjuvenilesand neonates,withestimatedbodylengthsbetween2and10.5meters.Conclusions/Significance:WeproposethattheMioceneGatunFormationrepresentsthefirstdocumentedpaleo-nursery areafor C.megalodon fromtheNeotropics,andoneofthefewrecordedinthefossilrecordforanextinctselachian.We thereforeshowthatsharkshaveusednurseryareasatleastfor10millionsofyearsasanadaptivestrategyduringtheirlife histories.Citation: PimientoC,EhretDJ,MacFaddenBJ,HubbellG(2010)AncientNurseryAreafortheExtinctGiantSharkMegalodonfromtheMioceneofPanama.PLoS ONE5(5):e10552.doi:10.1371/journal.pone.0010552 Editor: AnnaStepanova,PaleontologicalInstitute,RussianFederation Received February24,2010; Accepted April18,2010; Published May10,2010 Copyright: 2010Pimientoetal.Thisisanopen-accessarticledistributedunderthetermsoftheCreativeCommonsAttributionLicense,whichpermits unrestricteduse,distribution,andreproductioninanymedium,providedtheoriginalauthorandsourcearecredited. Funding: ThisprojectwasfundedbyNSFEAR0418042(,SigmaXiG2009100426( shtml),TheFloridaMuseumofNaturalHistory(,TheSmithsonianTropicalResearchInstitute(,TheMitchellHop eScholarship ( p.htm).Thefundershad noroleinstudydesign,datacollectionandanalysis,decisiontopublish,orpreparationofthemanuscript. CompetingInterests: Theauthorshavedeclaredthatnocompetinginterestsexist. *E-mail:pimientoc@ufl.eduIntroductionSharks,especiallylargespecies,arehighlymobileorganisms withacomplexlifehistoryandwidedistribution.Duringtheir lifetimetheygenerallyutilizethreetypesofareas:adultfeeding, reproductionandnurseries[1].Inmodernspecies,nurseryareas arehistoricallydefinedbythepresenceofgravidfemalesandfreeswimmingneonates.Itisalsoanareathatcanbesharedbyseveral sharkspecies,whereyoungsharksspendtheirfirstweeks,months oryears[2].Morerecentstudieshavedefinednurseryareasas geographicallydiscreteessentialzonesforsharksurvival[3]that providesthemwithtwotypesofbenefits:protectionfrom predation(mainlylargersharks[2])andabundantfoodresources. Productive,shallow-waterecosystemsthusprovidesharkssignificantprotectionfromlargerpredatorsand/orabundantfood resources,bothofwhichareessentialtosurvival[4]. TheGatunisahighlyfossiliferousNeogeneformationlocatedin theIsthmusofPanama(Figure1)withadiversefaunaofsharks [5–7].Itwaslocatedwithinamarinestraitthatconnectedthe PacificOceanandtheCaribbeanSeaduringthelateMiocene ( 10Ma)[8].Studiesofdifferenttaxa,includingtheexceedingly diversemolluscanfauna,indicatethatitwasashallow-water ecosystem( 25mdepth)withhighersalinity,meanannual temperaturevariations,seasonalityandproductivityrelativeto modernsystemsinthisregion[7,9–13].Overthepast20years,the GatunFormationlocalitieshavebeenextensivelyusedtoextract sedimentforconstruction.Duringthemorerecentyears,these extractionactivitieshaveincreasedsubstantially.Basedonour observationsmadeduringthetwopastyearsoffieldwork,wepredict thattheseoutcropswillsoonlikelybeexcavatedcompletely. Thereforeitistimelyandurgenttostudythefossilsoccurringin theseoutcropsbeforetheyarenolongeravailabletoscience. PLoSONE|www.plosone.org1May2010|Volume5|Issue5|e10552


FossilsharkswerefirstreportedfromPanamain1862[5].In 1984,thefirstdescriptionoftheelasmobranchsfromtheGatun Formationwaspublished[6].Morerecently,in2010the biodiversityofthefossilsharksfromtheGatunhasbeen documentedfromlargenewcollections,andcomprise16 recognizabletaxa.Thisworkalsoincludedpaleoecologicaland paleodepthanalysesthatsupportedtheinterpretationofthe paleoecologyoftheGatunFormationasshallow-waterhabitatina productiveenvironment[7]. Althoughitisnotverycommon,theextinct Carcharocles megalodon (Agassiz1843)isoneofthespeciesthatoccursinthe GatunFormation.Thetaxonomicassignmentofthisspecieshas beendebatedfornearlyacentury,andtherearethreepossible interpretations:(1)Someauthorsplace C.megalodon andother Figure1.Studyarea. A.LocationofPanamaandtheGatunFormation.TheshadedboxrepresentsthegeneralstudyareainnorthernPanama.B. Expandedgeologicalmap(from‘‘SeeBelow’’shadedboxinFig.A).ThismapshowstheexposuresoftheGatunFormationandsurroundingrock units(modifiedfromCoatesetal.,1992).ThetwofossillocalitiescollectedfromtheGatunFormationduringthisstudyinclude:(1)LasLomasand(2 ) IslaPayardi. doi:10.1371/journal.pone.0010552.g001 MegalodonNurseryArea PLoSONE|www.plosone.org2May2010|Volume5|Issue5|e10552


megatoothedsharkswiththeextantwhiteshark( Carcharodon carcharias )inthesamegenus( Carcharodon )andthereforethesame family(Lamnidae)[14–16].(2)Otherauthorsplace C.megalodon andmegatoothedsharksinadifferentgenus( Carcharocles )and family(Otodontidae)[17–23].Althoughaminoritypointof view,someworkersrecognize(3)megatoothedsharksasaseries ofchronospeciesofthegenus Otodus ,andplaceallmegatoothed sharksexcept C megalodon inthisgenus.Furthermore, C megalodon isassignedtothegenus Megaselachus ,basedonthe lossoflateralcusplets[24].Wefollowthesecondhypothesis; that Carcharoclesmegalodon and Carcharodoncarcharias belongto separategeneraindifferentfamilies.However,bothspecies belongtotheorderLamniformes,andintheabsenceofliving membersoftheOtodontidae, C carcharias shouldberegardedas ecologicallyanalogousspeciesto C.megalodon .Webasethis analogyonthefactthatbothspeciessharesimilarecological nicheswithpresumedsimilaritiesinbodyshape,feedinghabits, andoveralltoothandvertebralcentrummorphology.Even thoughthesespeciesarenotdirectrelatives,nootherextant lamniformspeciesshareasmanycharacteristicswith C.megalodon asdoes C.carcharias C.megalodon iswidelyregardedasthelargestsharktohaveever lived.Basedontoothcrownheight(CH),thisgiantreachedatotal length(TL)ofmorethan16m.Onesingletoothcanexceedmore than168mmoftotalheight[14].Thediagnosticcharactersof C. megalodon teethinclude:largesize,triangularshape,fineserrations onthecuttingedges,aconvexlingualface,aslightlyconvextoflat labialface,andalargev-shapedneck[7].Juvenilespecimensof C. megalodon canhavelateralcusplets[15],ornot[22].Thesizeand shapeoftheteethvarywithinthejaw:anteriorteetharelargeand symmetricalwhereasthelatero-posteriorteethareasymmetrical withslantedcrowns.Movingantero-posteriorlythroughthejaw, thereisaslightinitialincreaseinsizeoneithersideofthemid-line, followedbyaprogressivedecreasethatcontinuestothelasttooth, e.g.[25](FigureS1).Fossilteethof C.megalodon rangeinagefrom 17to2Ma(middleMiocenetoPleistocene)andhavea cosmopolitandistribution[7,14,16]. Ofrelevanceofthisstudy,twosharkpaleo-nurseryareashave previouslybeenproposed:thePaleoceneWilliamsburgFormation ofSouthCarolina,basedonthepresenceofjuvenileteethoffour lamnoidtaxa[26];andthelateOligoceneChandlerBridge FormationofSouthCarolina,basedontheabundanceofjuvenile Carcharocles teeth,accompaniedbysmallodontoceteandmysticete skulls,whichareassumedtobetheirpreyspecies[16].However, neitherofthecollectionsfromthesetwolocalitieshavebeen rigorouslyanalyzedandthusthepresenceofpaleo-nurseries remainedanecdotaluntilthepresentreport. Thepresenceofmammalsaspotentialpreydoesnot representevidenceofasharknurseryarea.Asknownfrom modernstudiesofsharks,themainpurposeofthenurseryareas isnotfeeding[1–4].Studieshaveshownthatsomesharkspecies donotconsumelargequantitiesoffoodduringtheirjuvenile stages[27–28].Evenwhenhigh-productivitynurseryareas provideamplefoodresourcesforjuvenilesharks,somespecies selectthesehabitatsmoreforpredatoravoidanceandnotfood consumption[3–4].Furthermore,somesharkspeciespresentan ontogeneticshiftinfeedingpatterns[29–32].Forexample,the lamnoidwhiteshark( C.carcharias )feedsmostlyonfishes (includingothersharks)duringtheirjuvenilestageandon mammalsduringtheiradultstage[33–35].Marinemammals arenotcommonlyfoundintheGatunFormation.Ontheother hand,bonyfishotoliths[36]andothersharkspecies[7]are abundant,representingafoodsourceforthemarinefaunathat livedinthisdiverseenvironment. Inthisstudy C.megalodon teethwerecollectedandmeasuredfromtwolocalitieswithintheGatunFormationofPanama (Figure1).Surprisingly,largeteethareuncommonwithspecimens recoveredhavingCHrangingbetween16to72mm(Figure2). TheobjectiveofthisworkistodetermineifthelateMiocene GatunFormationwasusedasanurseryareabyyoung C. megalodon .Accordingly,wecomparedthetoothsizesfromthe GatunFormationwiththosefoundinolderandyounger formationstodetermineifthesmallersizedistributionobserved isuniquetothespeciesduringthelateMiocene.Inaddition,we comparedthesesizeswithtoothsetsfromindividualsofdifferent lifestagestodetermineifthesmallsizeobservedisrelatedtoage, orpositionwithinthejaw.Finally,wecalculatedtheTLofall C. megalodon individualsfromtheGatunFormationtoestimatetheir lifestage.Theresultsobtainedinthisstudyfromtooth measurementcomparisonsandindividualtotallengthestimates allowedustodeterminetheageclass/sizeofindividualsthat inhabitedtheshallow-waterhabitatsofthelateMioceneGatun Formation, 10millionyearsago.ResultsandDiscussion TemporalcomparisonsofsimilarfaunasInmanycladesrepresentedinthefossilrecord,animals oftentimesshowageneraltendencytobecomelargerthrough time,i.e.,alsocalled‘‘Cope’sRule’’[37–38].Forexample,within lamnoidsharksthereisachronoclinaltrendtowardsincreasing sizeofspecieswithinthegenus Carcharocles from Carcharocles auriculatus to Carcharoclesangustidens toitslargerspecies, Carcharocles megalodon [16].However,thereisnoevidenceofsucha microevolutionarytrendwithinthesinglespecies C.megalodon throughtime,aswewillshowbelow. Inordertoknowifthesmallsizeobservedinthefossil C. megalodon fromtheGatunFormationisaspecialfeatureduringthe lateMioceneinapotentiallychronoclinallyevolvingspecies,we performedtoothsizecomparisonsthroughtimewithinother marinefaunasthathavesufficientlylargenumbersofspecimensof C.megalodon .Giventhefactthatthe C.megalodon fromtheCalvert FormationofMarylandareolder( 14Ma)andthe C.megalodon fromtheBoneValleyFormationofFloridaareyounger( 5Ma), comparingthesepopulationswith C.megalodon fromtheGatun Formationcandetermineifthereisalong-term,chronoclinal trendforsizeincrease,orif C.megalodon fromtheGatunFormation areunusuallysmall.Figure3showsthatbothlargeandsmalltooth sizesarefoundinthefaunasolderandyoungerthantheGatun Formation,andthusthereisnoobservedmicroevolutionarytrend forincreasedsizein C.megalodon overtime.Wethereforeassert thatthesmallsizeobservedintheGatunFormationisnotrelated tomicroevolutionaryshiftsinbodysize.Consequently,we demonstratestasisinbodysizewithinthespecies C.megalodon whichprovidesusimportantcontextinwhichtocompareancient populationsfromthelocalitiesdescribedabove.LifestagecomparisonsItisknownthatwithinanindividual, C.megalodon teethvary insizewithinthejaw,e.g.[15–16,25](FigureS1).Itcould thereforebearguedthatthesmallsizeobservedintheGatun Formationisrelatedtotoothposition,ratherthanjuvenilelife stageoftheindividuals.Inordertotestthis,wecomparedtooth sizesoftheGatunFormationspecimenswithassociatedtooth setsfromindividualsofdifferentlifestages(juvenileandadult) fromotherlocalities.Ourresultsindicatethatmostteethfrom theGatunFormationareclosetotheobservedrangeofaMegalodonNurseryArea PLoSONE|www.plosone.org3May2010|Volume5|Issue5|e10552


juveniledentition(Figure4),regardlessoftoothpositionwithin thejaw. ComparingtheGatunÂ’sisolatedteethwithtoothsetsof individualsfromdifferentlifestageshelpstodetermineifthe toothsizeobservedisrelatedwithtoothposition.Nevertheless,in ordertodeterminethelifestageofthoseanimalswereneonates, juvenilesoradults;itisnecessarytoestablishtotallengthestimates aswell,aspresentedbelow. Figure2.CarcharoclesmegalodoncollectionfromtheGatunFormation. Specimensandtheirrespectivecollectionnumbers.Onespecimen (CTPA6671)wasnotavailabletophotograph. doi:10.1371/journal.pone.0010552.g002 MegalodonNurseryArea PLoSONE|www.plosone.org4May2010|Volume5|Issue5|e10552


LifestageandtotallengthestimatesThetoothsizecomparisonsmadeinthisresearchsuggestthat thesmallsizeof C.megalodon teethfromtheGatunFormationisnot relatedtotemporaldifferenceswithinachronoclinallyevolving speciesortothetoothpositionwithinthejaw(asdescribedabove); butrathertheybelongtojuvenilesharks.Whenonlytheteethofa sharkspeciesarepreserved,life(ontogenetic)stagesofindividuals canbepredictedintwodifferentways:(1)studyingmorphological featuresoftheteethduringjuvenilestages;and(2)extrapolating totallengthusingtherelationshipbetweenbodysizeandtooth crownheight. (1)In C.megalodon ,teethofjuvenilessometimesdemonstratelateral cusplets[15]ornot[22].Forexample,UF237914(alateraltooth) exhibitslateralcuspletsandisassumedtobefromajuvenile.Onthe otherhand,UF237959(aloweranteriortooth)andUF237949(an upperanterior)arebothverysmallteeththatexhibitnolateral cusplets(Figure2).Thelatterteetharesmallthick,heart-shaped,and areconsideredtorepresentembryonic C megalodon teeth(Hubbell teeth).Theselatterteethretainthemorphologyofthespeciesevenat smallsizesanddonodemonstratelateralcusplets[22]. (2)Gottfriedetal.(1996)[14]madeinferencesaboutthe skeletalanatomyof C.megalodon basedoncomparisonswith ontogenetictrendsinthewhiteshark, Carcharodoncarcharias .They deducedthata C.megalodon fetuscouldreach 4m,juveniles 10.5m,andadultsmorethan10.5m( 17m).Basedon crownheights(CH)andfollowingtheworkofShimada(2003) [39],weestimatethetotallengths(TL)of C.megalodon specimens fromtheGatunFormation(Table1).BasedonGottfriedetal.Â’s inferences,thetotallengthestimatesmadeinthisresearchsuggest thatthe C.megalodon specimensfromtheGatunFormation representmostlyjuveniles(21individuals),withtotallengthsless than10.5m,whileafewspecimens(7individuals)areinterpreted asadults,withanestimatedtotallengthsbeyond10.5m (Figure5). Thereissomeexpectationtofindadultindividualsinsidea paleo-nurseryarea,alongwiththejuvenilesharksfortworeasons: (1)sharksconstantlyproduceandshedteeth[40],ifgravid femaleslaytheireggsorgivebirthinnurseryareas,onewould expecttofindsomelargerteeth;and(2)whilenurseryareasdo offersomeprotectionfromlargerpredators,theydonot Figure3.Temporalcomparisonsofsimilarfaunas. Comparisonsof Carcharoclesmegalodon toothmeasurements(CH:crownheight,CW: crownwidth),inmillimetersfromtheGatunFormation(lateMiocene),withisolatedteethfromayounger(BoneValley,earlyPliocene)andanolder formation(Calvert,middleMiocene),whichrepresentthreelocalitiesfromwhichthisspeciesisrelativelyabundant. doi:10.1371/journal.pone.0010552.g003 Figure4.Lifestagecomparisons. Comparisonsof Carcharoclesmegalodon toothmeasurements(CH:crownheight,CW:crownwidth)fromthe GatunFormationwithtoothsetsof:ajuvenilefromtheBoneValleyFormationandanadultfromtheYorktownFormation.Notethesizedifferencein relationwiththetoothpositions:largerteetharethemostanterior(e.g.A1,A2,L1,L2)whereassmallerteetharethemostlateral(e.g.L8,L9,l7,l 8,l9). Formoredetailsontoothpositions,seefigureS1. doi:10.1371/journal.pone.0010552.g004 MegalodonNurseryArea PLoSONE|www.plosone.org5May2010|Volume5|Issue5|e10552


necessarilykeepalllargeindividualsout[3],infact,nurseryareas areproductiveenvironmentswherecompetitionforfoodcanbe veryhigh[4].ConcludingRemarks:NurseryareahypothesisAsdescribedearlier,inadditiontonurseries,extantsharks utilizeadultfeedingandreproductionareas[1].Basedonwhatis knownaboutaggregationsoftheanalogousspecies,thewhite shark( C.carcharias ),wehavealsoconsideredthehypothesisthat thelateMioceneGatunFormationwasusedasanaggregationsite by C.megalodon forfeedingand/orreproductionratherthanasa nurseryarea.Followingtheiroceanicmigrations, C.carcharias individualsaggregateintheeasternPacific(alsocalledSOFAor SharkCafE ` )[41–42].Theyseasonallyreturntothispelagicarea thatissuggestedtobeusedforfeeding/foragingandmating [41–43].Furthermore, C.carcharias alsoaggregatesinvarious coastal‘‘hotspots’’wheretheyfeedaroundpinnipedcolonies [41–47].Nevertheless,basedonthepresenceofneonatesof C. megalodon ,thegenerallyhighproportionofjuvenileindividuals,the estimatedshallowdepthoftheGatunFormationandthescarcity oflargemammals,werejectthehypothesisoftheGatunasa primarilyareaforreproductionorfeeding. Inthisstudyweshowthattheabundanceofsmalltoothsize observedin C.megalodon specimensfromtheGatunFormationis notrelatedtoitstemporalpositionwithinachronoclinally evolvingspeciesortoothpositionwithinthejaw.Thus,the C. megalodon fromtheGatunFormationindicatesthedominant juvenilelifestageofindividualspresentfromthisfossillocality (withestimatedbodylengthsbetween2and10.5meters).The C. megalodon andassociatedmarineinvertebrateandvertebrate faunasfromthelateMioceneGatunFormationofPanama presentsthetypicalcharacteristicsofasharknurseryarea,i.e.,a shallow,productiveenvironmentthatcontainsjuvenilesand neonates(thelaterindicatingtheseindividualsprobablywere bornintheGatunarea).WethereforeproposetheMiocene GatunFormation,asanurseryareathatofferedjuvenile C. megalodon protectionfromlargerpredatorsandamplefood resources(i.e.fishes). Giventhat C.megalodon wasthelargestsharkthathaseverlived, itcouldbearguedthatthisspeciesmaynothaverepresenteda potentialpreyforothersharksandthereforenurseryareaswould notbeneeded.Inthisstudyhowever,wereportthatneonate individualsof C.megalodon fromthelateMioceneGatunFormation ofPanamacouldbeassmallas2mlong.Furthermore,many othersharkspeciesintheGatunFormationapparentlywere sympatricwithjuvenile C.megalodon ,includingpotentialpredators thatcanreachmorethan6moftotallength(e.g.thegreat hammerheadshark( Sphyrnamokarran )andtheextinctsnaggletooth shark( Hemipristisserra ))[7].Moreover,inspiteofajuvenile dominance,adultindividualsof C.megalodon (reachinguntil 17m ofTL)arealsofoundintheGatunFormation,representing additionalpotentialpredators.Withregardtomodernspecies, large-bodiedsharkssuchasthetigershark( Galeocerdocuvier )andthe greathammerhead( S.mokarran )alsousenurseryareas[48]. Additionally,ithasbeendemonstratedthatthemodernapexshark predatoroftheoceans(andtheanalogousspeciesof C.megalodon in thisstudy),thewhiteshark,usestheSouthernCaliforniaBightasa nurseryground[49]. Insummary,thisstudyrepresentsthefirstdefinitiveevidenceof anancientsharknurseryareafromtheNeotropics.Sharksarea verysuccessfulgroupthathasbeencommoninouroceansforat least400millionyears[40].Thisresearchpresentsevidencethat sharkshaveusednurseryareassinceancienttimes,i.e.,foratleast 10millionyears,andthereforeextendstherecordofthisbehavior andadaptivestrategybasedonfossilevidence. Figure5.Totallengthhistogram. Frequencyof Carcharoclesmegalodon individualsatdifferentlifestagesbasedonGottfriedetal.[14].Neonates of C.megalodon reachuntil4m;juvenilesuntil10.5m,andadultsmorethan10.5m. doi:10.1371/journal.pone.0010552.g005 MegalodonNurseryArea PLoSONE|www.plosone.org6May2010|Volume5|Issue5|e10552


MaterialsandMethodsCarcharoclesmegalodon teetharerelativelyrareintheGatun Formation.Ofmorethan400teethoffossilsharkscollectedfrom theGatunFormationbetween2007and2009representing16 taxa,atotalof28specimens(Figure2)of C.megalodon havebeen collected.Fossilsdonotprovidearecordoflifeascompleteas whenstudyinglivingorganisms.Forthatreasonandalsobecause oftherarityofthisspeciesintheareaofstudy,weconsiderour samplesizeadequate.Inaddition,itisurgenttostudythefossilsof aformationthatwillsoondisappearduetotheincreasing excavations. ThetwolocalitiesstudiedintheNeogenemarinesedimentsof theGatunFormationofPanama(Figure1),cropoutinabroad areainnorth-centralPanamaandhavebeenproposedtobelate Miocene,spanningfromabout12to8.4Ma[9].Thematerials werecollectedmainlybysurfaceprospectingbythePanama CanalProjectFieldTeamoftheCenterofTropicalPaleobiology andArchaeology(CTPA)oftheSmithsonianTropicalResearch Institute(STRI),aswellastheUniversityofFlorida(UF)scientists. SomeofthespecimenscollectedaredepositedintheFlorida MuseumofNaturalHistory(FLMNH)andaredesignatedwitha UFcataloguenumberwhichareavailableinitsdatabase:http:// specimensaredesignatedwithaCTPAorATnumberandare partoftheSTRIcollection. Crownheight(CH)andwidth(CW)(FigureS2)ofallspecimens weremeasured(Table1,S1,S2,S3andS4)usingdigitalcalipers. Inordertocalculatedimensionsofincompletespecimens,CWvs. CHdatawereplottedandalineregressionwascalculated(Figure S3).Measurementswerethencomparedwithisolatedteethfrom geologicallyyoungerandoldercollectionsandwithdifferenttooth setsfromindividualsofdifferentlifestages.Thespecimens’total lengths(TL)werecalculatedbasedontheirCH.TemporalcomparisonsofsimilarfaunasIsolatedteethfromtheyoungerBoneValleyFormation, Florida(earlyPliocene, 5Ma)[50–51],fromtheVertebrate PaleontologyCollectionattheFLMNHinGainesville,Florida, weremeasured(TableS1)andcomparedwiththeGatunteeth. Additionally,isolatedteethfromtheolderCalvertFormation, Maryland(middleMiocene, 14Ma)[52],fromtheVertebrate PaleontologyCollectionattheU.S.NationalMuseumof NaturalHistory(NMNH),inWashington,D.C,werealso measured(TableS2)andthencomparedwiththeGatun Formationteeth.LifestagecomparisonsToothsizesoftheGatunisolatedteethweremeasuredand comparedwithtwo C.megalodon associatedtoothsetsofdifferent lifestagesfromtheHubbellcollectionatGainesville,FL.The adulttoothsetisfromtheYorktownFormation,NorthCarolina (earlyPliocene)[52](TableS3).Andthejuveniletoothsetisfrom theBoneValleyFormation,Florida(earlyPliocene)[50–51] (TableS4).TotallengthestimatesAsdescribedabove,theextantwhiteshark( Carcharodon carcharias ),hasbeenusedasageneralecologicalanalogtothe extinct Carcharoclesmegalodon .Likewise,previousstudieshave assertedthatteethof C.carcharias canbeusedtoestimatethetotal lengthof C megalodon [14,38].Basedon C.carcharias toothheight andtotallengthratios,wehavemeasured C.megalodon toothCH toextrapolateitsTLestimatesbasedontheworkofShimada (2003)[39]onthewhiteshark,whereeverytoothpositioninthe jawcorrespondstooneregressionequationthatcalculatesits bodysize(TableS5).Weassignedarangeofpossiblepositionsto theGatunteethandestimatedtheTLofeveryspecimenby calculatingitfromtheaverageamongthedifferentpositions whereeverytoothcouldhavebelonged(TL,Table1).Wethen inferredthelifestageofevery C.megalodon ,byextrapolatingit fromtherelationshipbetweenbodysizeandlifestagein C. carcharias followingGottfriedetal.(1996)[14].Webasedour C. megalodon estimatesonextrapolationsfromtheextant C.carcharias giventheirsimilaritiesinbodyshape,feedinghabits,andtooth andvertebralmorphology.Inaddition,bothspeciesbelongtothe sameorder(Lamniformes),andintheabsenceoflivingmembers oftheOtodontidae, C carcharias isthemostanalogousspecies available. Table1. Carcharoclesmegalodon isolatedteeth measurementsfromtheGatunFormation,Panama.SpecimenCW(mm)CH(mm)Position**TL(m)*** UF23789853.050.0*A1–A25.9 UF23791431.446.4L1–L58.0 UF23794935.732.9A1–A23.9 UF23795047.754.2a27.3 UF23795126.817.6L1–L53.1 UF23795243.231.3L1–L55.4 UF23795330.924.5l1–l57.2 UF23795441.741.2A1–A24.9 UF23795528.428.5A1–A23.4 UF23795644.928.1l4–l616.8 UF23795726.7*19.4L6–L913.8 UF23795916.116.0a1–a22.2 UF24280131.227.5*L1–L5,l1–l56.4 UF24280245.141.0L1–L57.1 UF24280340.834.7L1–L56.0 AT04-17-143.243.8a1–126.2 AT04-41-260.356.4A1–A26.7 AT06-9-157.760.1A1–A27.1 UF24584420.611.2l5–l710.0 UF24585273.270.9*L2–L410.8 UF24588539.636.6L1–L35.2 UF24588645.640.5L1–L57.0 UF24599631.8*25.9l3–l613.1 UF24599562.263.2a311.0 UF24600235.024.5L7–L911.5 UF24600352.445.4L1–L36.4 UF24592523.219.2*L6–L913.7 CTPA667174.772.3A1–A28.6 *Incompletespecimens.Toothcrownwidth(CW)andcrownheight(CH) measurementspredictedusingthelineequation:y=mx + b(seefigureS2). **Rangeofpossiblepositionswhereeverytoothcouldhavebelonged(see figureS1forpositiondetails). ***TotalLength(TL)estimatedbasedonShimada(2003)[39](seetableS1).The valuepresentedwascalculatedfromtheaverageamongthedifferentpositions whereeverytoothcouldhavebelonged. doi:10.1371/journal.pone.0010552.t001 MegalodonNurseryArea PLoSONE|www.plosone.org7May2010|Volume5|Issue5|e10552


SupportingInformationFigureS1Representationofa Carcharoclesmegalodon dentition. Toothsizeandshapevariesgreatlywithinthejaw:mostanterior teetharelargerandsymmetrical;mostlateralteetharesmaller andasymmetrical.Capitallettersrepresentupperteeth,lowercase lettersrepresentlowerteeth.LetterA(a)isforanteriorandL(l)for lateral.AdaptedfromGottfriedetal.(1996)[14]. Foundat:doi:10.1371/journal.pone.0010552.s001(0.16MBTIF)FigureS2Toothmeasurementcodesanddimensions.CW representscrownwidthandCHrepresentscrownheight.All measurementsweretakeninmillimeters. Foundat:doi:10.1371/journal.pone.0010552.s002(0.07MBTIF)FigureS3Toothmeasurementslineregressions.A.Known crownwidth(CW).Lineregressioncalculatedwhenispossibleto measuretheCW(i.e.CWinthexorindependentaxes)butthe CHisunknownduetofossilpreservation.B.Knowncrownheight (CH).Lineregressioncalculatedwhenispossibletomeasurethe CH(i.e.CHinthexorindependentaxes)buttheCWisunknown duetofossilpreservation. Foundat:doi:10.1371/journal.pone.0010552.s003(0.72MBTIF)TableS1Carcharoclesmegalodon isolatedteeth,fromtheBone ValleyFormation,Florida,USA. Foundat:doi:10.1371/journal.pone.0010552.s004(0.06MB DOC)TableS2Carcharoclesmegalodon isolatedteeth,fromtheCalvert Formation,Maryland,USA. Foundat:doi:10.1371/journal.pone.0010552.s005(0.07MB DOC)TableS3Adult Carcharoclesmegalodon associatedtoothset,from theYorktownFormation,NorthCarolina,USA. Foundat:doi:10.1371/journal.pone.0010552.s006(0.04MB DOC)TableS4Juvenile Carcharoclesmegalodon associatedtoothset,from theBoneValleyFormation,Florida,USA. Foundat:doi:10.1371/journal.pone.0010552.s007(0.04MB DOC)TableS5TotallengthregressionbasedonCHofeverytooth position,fromShimada(2003)[39]. Foundat:doi:10.1371/journal.pone.0010552.s008(0.04MB DOC)AcknowledgmentsWethankC.JaramilloforfacilitatingthematerialcollectedinPanama;to A.Rincon,JamesWilson,CesarSilva,SandraSuarez,C.Montesandthe PanamaCanalProjectFieldTeamintheCTPAatSTRIforhelpingwith thecollectionofthematerial;toF.RodriguezandA.O’Deaforfacilitating previouscollectedmaterial(numberedAT);andtothe DirecciondeRecursos Minerales ofPanamaforcollectingpermits.ThankstoD.BohaskaandR. PurdyfromtheNationalMuseumofNaturalHistoryforaccessto collections.WethankG.Morganforbeneficialsuggestionsaboutthis research.WealsothanktoA.Hendryforreviewingearlierversionsofthis manuscript.WearegratefulfortheconstructivecommentsmadebyA. Stepanova,MichaelGottfriedandananonymousreviewer,which substantiallyimprovedtheoriginalversionofthemanuscript.Finally thankstoJ.McLaughlinforhisconstantsupport.ThisisUniversityof FloridaContributiontoPaleobiologynumber629.Anyopinions,findings, conclusions,orrecommendationsexpressedinthispaperarethoseofthe authorsanddonotnecessarilyreflecttheviewsoftheNationalScience Foundation.AuthorContributionsConceivedanddesignedtheexperiments:CPDJEBJM.Performedthe experiments:CP.Analyzedthedata:CP.Contributedreagents/materials/ analysistools:CPGH.Wrotethepaper:CP.Intellectualsupportand editorialinput:DJEBJMGH.References1.Alejo-PlataC,Gomez-MarquezJL,RamosS,HerreraE(2007)Presenceof neonatesandjuvenilescallopedhammerheadsharks Sphyrnalewini (Griffith& Smith,1834)andsilkysharks Carcharhinusfalciformis (Muller&Henle,1839)inthe Oaxacacoast,Mexico.RevBiolMarOceanog42:403–413. 2.CastroJI(1993)ThesharknurseryofBullsBay,SouthCarolina,withareviewof thesharknurseriesofthesoutheasterncoastoftheUnitedStates.EnvironBiol Fish38:37–48. 3.HeupelMR,CarlsonJK,SimpfendorferCA(2007)Sharknurseryareas: concepts,definition,characterizationandassumptions.MarEcolProgSer337: 287–297. 4.HeithausMR(2007)Nurseryareasasessentialsharkhabitats:atheoretical perspective.AmericanFisheriesSocietySymposium50:3–13. 5.BlakeSF(1862)FossilsharkteethatPanama.TheGeologist5:316. 6.GilletteDD(1984)AmarineichthyofaunafromtheMioceneofPanama,and theTertiaryCaribbeanfaunalprovince.JVertebrPaleontol4:172–186. 7.PimientoC(2010)Systematics,paleobiology,andpaleoecologyoflateMiocene sharks(Elasmobranchii,Selachii)fromPanama:integrationofresearchand education.Gainesville:UniversityofFlorida.131p. 8.CoatesAG(1996)LithostratigraphyoftheNeogenestrataoftheCaribbean coastfromLimon,CostaRica,toColon,Panama.In:CollinsLS,CoatesAG, eds.APaleobioticSurveyofCaribbeanFaunasfromtheNeogeneoftheIsthmus ofPanama.Bulletin357.Ithaca:PaleontologicalResearchInstitute,Ithaca.pp 17–38. 9.CollinsLSA,CoatesG,BerggrenWA,AubryMP,ZhangJJ(1996)Thelate MiocenePanamaisthmianstrait.Geology24:687–690. 10.CoatesAG,ObandoJA(1996)ThegeologicevolutionoftheCentralAmerican Isthmus.In:JacksonJBC,BuddAF ,CoatesAG,eds.Evolutionand environmentintropicalAmerica,UniversityofChicagoPress;Universityof ChicagoPress.pp21–56. 11.GussoneN,EisenhauerA,TiedemannR,HaugGH,HeuserA,etal.(2004) ReconstructionofCaribbeanseasurfacetemperatureandsalinityfluctuationsin responsetothePlioceneclosureoftheCentralAmericanGatewayandradiative forcing,using D44/40Ca, D18OandMg/Caratios.EarthPlanetScLett227: 201–214. 12.HaugGH,TiedemannR,ZahnR,RaveloAC(2001)RoleofPanamauplifton oceanicfreshwaterbalance.Geology29:207–210. 13.TeranesJL,GearyDH,BemisBE(1996)Theoxygenisotopicrecordof seasonalityinNeogeneBivalvesfromtheCentralAmericanIsthmus.In: JacksonJBC,BuddAF,CoatesAG,eds.Evolutionandenvironmentintropical America,UniversityofChicagoPress;UniversityofChicagoPress.pp105–129. 14.GottfriedMD,CompagnoLJV,BowmanSC(1996)Sizeandskeletalanatomy ofthegiantmegatoothshark Carcharodonmegalodon .In:KlimleyAP,AinleyDG, eds.Greatwhitesharks:thebiologyof Carcharodoncarcharias .SanDiego: AcademicPress.pp55–89. 15.ApplegateSP,Espinosa-ArrubarrenaL(1996)Thefossilhistoryof Carcharodon anditspossibleancestor, Cretolamna :astudyintoothidentification.In: KlimleyAP,AinleyDG,eds.Greatwhitesharks:thebiologyof Carcharodon carcharias .SanDiego:AcademicPress.pp19–36. 16.PurdyR(1996)Paleoecologyoffossilwhitesharks.In:KlimleyAP,AinleyDG, eds.Greatwhitesharks:thebiologyof Carcharodoncarcharias .SanDiego: AcademicPress.pp67–78. 17.JordanDS,HannibalH(1923)FossilsharksandraysofthePacificSlopeof NorthAmerica.BullSouthCalifAcadSci22:27–63. 18.CasierE(1960)Notesurlacollectiondespoissonspaleochnesetiochnesde l’Enclavede(Congo).AnnalesMuseumRoyalCongoBelge(A.30)1,2.pp1–28. 19.GluckmanLS(1964)SharksofPaleogeneofstratigraphicsignificance.Moscow: NaukaPress.229p. 20.CappettaH(1987)ChondrichthyesII.MesozoicandCenozoicElasmobranchi. 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Time 7.5 15.0 22.5 30.0 Pleistocene L. Pliocene E. Pliocene L. Miocene M. Miocene E. Miocene Recent PastBody size and geographic distribution of the extinct shark Megalodon (Carcharocles megalodon) Background is the biggest shark that ever existed. It lived from 18 to 2 million years ago tion 3 1 2 3Body size Geographic distribution 0 14 28 41 55 69 83 96 110 0 11 22 33 44 55 66 77 88 99 110 (nursery area) o Late Pliocene Early Pliocene Late Miocene Middle Miocene Early Miocene Time Pleistocene Pleistocene the early Pliocene before its extinction 2 Ma 20 40 60 80 100 14Ma 12 Ma 10Ma 5Ma 6MaRecent Pleistocene L. Pliocene E. Pliocene L. Miocene M. Miocene E. Miocene Time Past 0 20 40 60 80 100 120 140 160 180 2 4 6 8 10 12 14 16 18 MaNursery area 5cm References: and its fornia. Conclusions over geologic time Insights Future questions Questions Acknowledgments: Special thanks our advisors, B. MacFadden & F. Smith. We would also want to thank C. Jaramillo, D. Jones, B. Silliman, G. Morgan, J. Grin, C. Symister, A. Hendy, D. Bohanska, S. J. Godfrey, PCP-PIRE, STRI, CTPA, ACP, MICI, USNMNH and The Calvert Marine Museum. This project has been funded by FLMNH, NSF, Sigma Xi, UF-LAS. Funds to present this poster were provided by NSF, STRI and the UF-Biology department. Implications tion of modern sharks Methods