Abstract: Dinosaurs on Ice: Jurassic Dinosaurs from Antarctica

William R. Hammer

During the austral summer of 1990-1991 the first Antarctic Jurassic dinosaurs were collected from Mt. Kirkpatrick near the Beardmore Glacier, approximately 600 km from the geographic South Pole. At least six taxa, four of which are dinosaurs, are represented in the fauna collected from this single locality.

Most of the bones belong to a previously unknown large theropod, Cryolophosaurus (frozen crested reptile). This animal has a unique display crest that sits above the orbits and runs across the skull, perpendicular to its length. This highly ornamental crest apparently was used for some type of visual display, perhaps during a mating ritual. Cryolophosaurus is an early relative of the late Jurassic carnivores Allosaurus and Monolophosaurus. The disarticulated skeleton of Cryolophosaurus indicates that it had been scavenged after death. In addition, broken teeth from smaller scavenging theropods were found near gnawed sections of the bones. The pattern and density of the serrations on these teeth indicate the presence of at least two differen theropod scavengers.

A partially articulated foot and part of the femur of a large prosauropod were found among the scattered bones of this Cryolophosaurus. This animal is similar to Plateosaurus from Europe and the Chinese Lufengosaurus. Several long cervical ribs that may belong to the prosauropod are preserved in the mouth of the Cryolophosaurus specimen, suggesting the large carnivore was feeding on this animal when it died. Since the ribs extend all the way back to the neck region, it is probable that this cryolophosaur actually choked to death on its prey.

A single postcanine tooth of a tritylodont occurs with the dinosaur remains. This tooth, which may have been stomach contents of the cryolophosaur, belongs to a beaver-size early relative of modern mammals. Tritylodonts have very distinctive complex molar teeth with three rows of cusps (hence the name tritylodont) and were similar to some modern rodents in their adaptations.

Approximately 50 m from the site containing the concentration of bones described above, a single humerus from a pterosaur, or flying reptile, was found. This animal belongs to an early, primitive group of pterosaurs called dimorphodontids. Similar pterosaurs are known from other continents, particularly Europe.

The presence of the large tritylodont and the plateosaurid prosauropod suggest an Early Jurassic age for this Antarctic fauna. This makes Cryolophosaurus the oldest known member of the allosaurid family, approximately 50 m.y. older than the Late Jurassic Allosaurus. This is also the first allosaurid from any southern continent, indicating the group was not restricted to the north but had a Pangean distribution.

AAPG Search and Discovery Article #90948©1996-1997 AAPG Distinguished Lecturers