Terrestrial geology and geophysics

Comments on the fossil vertebratesfrom the Falla Formation Jurassic,

Beardmore Glacier region,Antarctica

WILLIAM R. HAMMER AND WILLIAM J. HICKERSON

Augustana CollegeRock Island, Illinois 61201

The first fossil vertebrates from the Falla Formation of thecentral Transantarctic Mountains were collected during the 1990-1991 austral summer from Mt. Kirkpatrick in the BeardmoreGlacier region (Hammer et al. 1991; Hammer 1992). Over 60bones were recovered from one small exposure of tuffaceoussiltstone near the top of the formation, and three isolated boneswere found within 30 meters of the bone concentration at aboutthe same stratigraphic level (Hammer et al. 1991). Althoughmuch of the material collected remains in the matrix, the prepa-ration of the fossils is progressing, and at least four types ofanimals have been recognized in the fauna.

Three of the four taxa are dinosaurs. Much of the skeleton(perhaps over 50 percent of a new, large, carnivorous theropodcarnosaur) was recovered, and to date, most of the skull, pelvis,and a femur of this animal has been prepared. Its most uniquefeature is its large, furrowed crest that rises perpendicular to thelong axis of the skull, just posterior to well-developed nasalridges. The skull specimen, which is broken anteriorly, is ap-proximately 55 centimeters in length; the actual skull length isprobably 15 centimeters longer. The size and general features ofthe skull liken it to larger carnosaurs from other continents, suchas the North American genus Allosaurus and the ChineseYangchuanosaurus. However, the crest and postorbital construc-tion of the skull indicate that the antarctic carnosaur represents anew genus. The pubis and ischium are similar to that ofPiatnizkysaurus from southern Argentina which, geographically,is the closest carnosaur locality to the Antarctic. Unfortunately,Piatnizkysaurus is represented mainly by postcranial remains andlimited information is available about its skull structure.

At this point, few remains of the other animals have beenidentified, hence their affinities to the dinosaurs are less certain.A partially articulated pes including four large metatarsals ap-pears to represent a sizable prosauropod or sauropod. The distalend of a large femur may also belong to the same animal. Inaddition, several small, serrated teeth of scavenging theropodswere found in the matrix near the gnawed end of the carnosaurischium.

A single, small humerus that was one of the isolated bonesfound near the bone concentration belongs to a pterosaur. This

humerus is hollow, has the very distinctive broad medial end thatis characteristic of pterosaurs, and is larger than the humeri offorms such as Pterodactylus from the Jurassic Solenhofen Forma-tion (Wellenhofer 1970).

The nature of this fauna suggests that the upper portion ofthe Falla Formation is of Jurassic age. Similarly, advanced carno-saurs from other continents are Jurassic to early Cretaceous inage. Allosaurus and Yangchuanosaurus, for example, are late Juras-sic (Molnar, Kurzanov, and Dong 1990; Zhiming 1983; Molnar,Flannery, and Rich 1985). Piatnizkysaurus, the only other well-known carnosaur from a southern continent, is Middle Jurassic inage. Previously, the Dicroidium beds below the upper portion ofthe Falla Formation and the age of the overlying Kirkpatrickbasalts place a Late Triassic to Middle Jurassic age constraint onthis unit. Thus, the carnosaur indicates that the upper part of theFalla Formation is probably closer to the Middle Jurassic age ofthe basalts.

The Mt. Kirkpatrick fossils represent the first Jurassic terres-trial vertebrate fauna known from the antarctic continent. Thepterosaur and dinosaurs also represent the first members of theOrder Pterosauria and the Order Saurischia from Antarctica. Thepreviously reported Cretaceous dinosaurs from islands off theAntarctic Peninsula, a hypsilophodont and an ankylosaur, bothbelong to the dinosaurian Order Ornithischia (Hooker, Milner,and Sequeira 1991; Gasparini et al. 1987).

This work was supported by National Science Foundationgrants DPP 88-17023 and DPP 91-18620.

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