THE WING OF TITANIS WALLERI
(AVES:PHORUSRHACIDAE) FROM THE LATE
BLANCAN OF FLORIDA
Robert M. Chandler
Biological Sciences, Volumne 36, Number 6, pp. 175-180
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Publication date: July 6th, 1994
THE WING OF TITANIS WALLERI
(AVES:PHORUSRHACIDAE) FROM THE LATE BLANCAN
Robert M. Chandler'
Titanis walleri Brodkorb (1963:113) is the only known member of the South
American avian family Phorusrhacidae to have successfully emigrated north during
the Great American Interchange at the end of the Tertiary about 2.5 Ma (i.e., late
Pliocene; Webb 1991:266). Titanis and its closest relatives in the subfamily
Phorusrhacinae were flightless ground predators from one and one half to two
meters tall. Their skulls were laterally compressed for shredding their prey. The
holotype tarsometatarsus (UF 4108) and the first phalanx of Digit III (UF 4109) of
this remarkable bird remain the only published fossils. Field crews from the
Florida Museum of Natural History, led by Vertebrate Paleontology curators
Clayton Ray and later by S. David Webb, continued to work the type locality (Santa
Fe River lA and IB) through the 1960s. Santa Fe 1A is a mid-channel deep-water
basin where the fossils accumulate. Santa Fe lB contains inplace sediments from
which the fossils are eroding. Additional fossils of Titanis were collected by these
field crews, but were not identified as such until recently.
Carr (1981:91-94) identified 47 species, including T. walleri, from the early
Pleistocene avifauna of Inglis 1A, Citrus County. Among the referred material for
Titanis were several skeletal elements including a left carpometacarpus, which has
not been found at the Santa Fe River. Inglis IA is an early Irvingtonian sinkhole
deposit (Webb 1974:29; Meylan 1982:3-4). The only other locality in Florida
where Titanis has been found is Port Charlotte, Charlotte County, on a canal spoil
pile. This record is based on a digit II, phalanx 2 (UF 124228).
In 1993, with the financial support of the Philip M. McKenna Foundation,
field crews from the Florida Museum of Natural History began diving at the type
locality of Titanis in search of additional phorusrhacoid fossils. I have relocated
1 The author is a Post-doctoral Research Asistant in Ornihology an Venabrate Paleamology at the Florida Museum of Natural History.
University of Florida, P. 0. Box 117800, Gainesville FL 32611-7800 U. S. A.
Chandler, R. M. 1994. The Wing of Titanis walleri (Aves:Phonusrhacidae) from the Late Blancan of
Florida. Bull. Florida Mus. Nat. Hist., Biol. Sci. 36(6):175-180.
BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL. 36(7)
Santa Fe 1B, the in-place sediments, and found that it is a bone bed. The most
significant new fossil recovered to date is the proximal end of a left humerus (UF
137839) of Titanis walleri. This is the first Titanis humerus known. Also, it is the
first humerus correctly identified for the group of phorusrhacines (Andrewsornis,
Andalgalornis, and Phorusrhacus), which are the closest relatives of Titanis
The left proximal humerus (UF 137839, Santa Fe River IB) is broken just
distal to the external tuberosity and the head is missing (Fig. 1 A-D). It is very
large and robust with a palmoaconally flattened shaft. The deltoid crest is
perpendicular to the trailing edge of the shaft on the palmar surface. The shaft is
not hollow, but it has a greatly reduced pneumatic network of bone extending from
below the head distad through the shaft and also into the deltoid crest. The leading
edge of the shaft is densely packed bone. The raised bicipital surface is distinctly
demarcated and the bicipital furrow is broad and deep.
The left carpometacarpus (UF 30003, Inglis IA) is robust but short relative to
the depth of the proximal end (Fig. 2 A-E). The carpal trochlea is broad and
almost vertical in orientation not extending distad below metacarpals I and II.
Metacarpal I is rounded and the facet for the pollex is a ball joint about 7mm in
diameter. Metacarpals II and III are both slightly bowed. An enlarged tubercle
below the proximal symphysis provides insertion for the M. ulni-metacarpalis
Recently, I have studied the phorusrhacoids in the collections at the American
Museum of Natural History and the Field Museum of Natural History and have
discovered that the long-standing ideas about phorusrhacine wing structure are
incorrect. In the past, the wings of these large ground predators have been
modelled after the smaller psilopterine sister group because more complete
skeletons of psilopterines are known. The shaft of the humerus of psilopterines is
curved and rod-like in cross section. The humerus and carpometacarpus show that
Titanis and its closest relatives have a strong, robust wing instead of a small,
paedomorphic wing like ratites (e.g., rheas and ostriches) or a rod-like humerus as
in the psilopterines. The almost vertical carpal trochlea of the carpometacarpus of
Titanis shows that the manus was held extended, as in penguins, and could not be
folded under the ulna as in other birds.
Popular accounts illustrate these large phorusrhacines using their small wings
for balance like ratites (Marshall 1978; 1994). It is now clear that Titanis had a
much stronger wing architecture possibly equipped with a large claw. The claw
hypothesis is based on the presence of a ball joint for the facet of Metacarpal I (Fig.
3A, B), which is unique in birds. This ball joint would allow the pollex to be very
moveable and more useful. The claws could have been used to keep struggling
prey, which may have had horns or antlers, from injuring the attacker.
Another intriguing discovery from the Santa Fe River includes two
quadratojugals. Both are from large adult (completely ossified) phorusrhacines,
but they have different qualitative articular characters and differ in size. The
CHANDLER: TI7TANIS WALLERI WING
larger right quadratojugal (UF 57585) is from an individual the size of Titanis,
whereas, the left quadratojugal (UF 57580) is significantly smaller. These
elements are evidence for either sexual dimorphism in Titanis or that there is a
second undescribed species represented by the smaller individual. Sexual
dimorphism has not been proven to be present in the smaller psilopterine
phorusrhacoids, which are more abundant in collections.
The skeletal material of Titanis now represented in the Vertebrate
Paleontology collection at the Florida Museum of Natural History includes cranial
pieces, vertebrae, and portions of the wings and legs. Hopefully with the continued
success of this Santa Fe River project we will achieve a more comprehensive view
of Titanis and its relationship to other phorusrhacoids.
I thank the Philip M. McKenna Foundation for supporting this project. I want to thank the owners
and the management of Ginnie Springs, particularly Wes Skiles, for their cooperation and interest in this
project. I received travel awards from the American Museum of Natural History and the Field Museum of
Natural History to study fossils in those collections. Scott Lanyan (Birds) and John Bolt (Vertebrate
Paleontology), Field Museum; and Larry Martin, Museum of Natural History, The University of Kansas,
loaned important specimens to me for this study. Janis Brown, an enthusiastic volunteer diver, made the
significant find of the humerus of Titanis. Early versions of this manuscript were improved by critical
comments by Linda Dryden Chandler, Steven D. Emslie, S. David Webb, and W. Mark Whitten. The
drawings were skillfully done by Linda Dryden Chandler. This is University of Florida Contribution to
Paleontology Number 443.
Brodkorb, P. 1963. A giant flightless bird from the Pleistocene of Florida. The Auk 80(2):111-115.
Carr, G.E.S. 1981. An early Pleistocene avifauna from Inglis, Florida. Ph.D. dissertation, Univ. Florida,
Gainesville, 161 pp.
Marshall, L.G. 1978. The terror bird. Field Mus. Nat. Hist. Bull. 49(9):6-15.
Marshall, L.G. 1994. The terror birds of South America. Scient. Amer. 270(2):90-95.
Meylan, P.A. 1982. The squamate reptiles of the Inglis IA Fuana (Irvingtonian: Citrus County, Florida.
Bull. Florida State Mus., Biol. Sci. 27(3):1-85.
Webb, S.D. 1974. Chronology of Florida Pleistocene mammals. Pp. 5-31 in S.D. Webb, ed. Pleistocene
Mammals of Florida. Univ. Presses Florida, Gainesville.
Webb, S.D. 1991. Ecogeography and the Great American Interchange. Paleobiology 17(3):266-280.
BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL. 36(7)
S .... "" .. pectoral
Figure 1. Proximal left humerus of Titanis walleri, UF 137839. (A and C) Anconal view. (B and D)
Palmar view. Scale equals 2 cm.
metacarpal I facet .
.. / c carpal
metacarpal tubercle/ trochle1
Smetacarpal I facet
a metacarpal tubercle
Figure 2. Left carpometacarpus of Titanis walleri, UF 30003. (A and u) ....ew. (B and E) Internal view. (C) Proximal view. Scale equals 2 cm.
C D -<
Figure 3. The range of motion for the pollex of the left carpometacarpi with a ball-joint (A and B), Titanis walleri, UF 30003; and with a
flat facet (C and D), the modem Red-legged Seriema, Cariama cristata, FMNH 105635. The carpometacarpi in this figure are drawn to
approximately equal size.
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