Antarctica before the Dinosaurs: Triassic Vertebrates from the Transantarctic Mountains
William R. Hammer, Department of Geology, Augustana College
Prior to the discovery of the first dinosaurs from the southern Transantarctic Mountains during
the austral summer of 1990-91, older fossil vertebrate faunas were known from a number of Early and
Middle Triassic sites in the same region. The very first vertebrate fossil, a fragmentary temonspondyl
amphibian jaw, was collected during the 1967-68 season by Peter Barrett, a New Zealand stratigrapher.
This discovery led to the first two National Science Foundation funded Antarctic expeditions by
vertebrate paleontologists to look for fossils in the southern Transantarctic Mountains in 1969-70 and
1970-71. These expeditions were led by Ned Colbert, a prominent vertebrate paleontologist who had
recently retired from the American Museum of Natural History. During these two expeditions numerous
fossils of Early Triassic tetrapods were discovered at a number of sites near the Beardmore and
Shackleton Glaciers.
After these first two paleontological expeditions to Antarctica, John Cosgriff, a professor of
paleontology at Wayne State University, was asked by Colbert to launch another expedition to the
southern- most continent in the early 1970’s. After several delays due to problems with aircraft, the
Cosgriff expedition finally was funded for the 1977-78 season. This expedition led to the discovery of
many new Early Triassic taxa in the Cumulus Hills area near the Shackleton Glacier. After that expedition
Augustana paleontologist Bill Hammer, who was at the time a post-doctoral student of Cosgriff’s and
had accompanied him on the 77-78 expedition, became the lead Principal Investigator on the project.
Hammer joined the faculty at Augustana College in 1981, and since then he has led seven additional
expeditions to Antarctica in search of vertebrates, including the 1985-86 expedition which resulted in
the discovery of a new Middle Triassic fauna in the Gordon Valley near the Beardmore Glacier and the
1990-91 expedition that led to the discovery of the first Jurassic dinosaur from Antarctica. In 2003 Nate
Smith, then a graduate student and a former student of Hammer’s, became involved in this ongoing
research. On the last expedition in 2010-11 Smith, who recently finished a PhD at the University of
Chicago and is now a member of the faculty at Howard University, became a co-principal investigator on
the dinosaur project. In this abstract I will summarize the Triassic faunas as a lead into Smith’s abstract
on the dinosaur fauna.
The Early Triassic Antarctic fauna is dominated by a variety of synapsids, an extinct group that
links the reptiles with the mammals. Included in this assemblage is the odd herbivorous synapsid,
Lystrosaurus, whose discovery in Antarctica in 1970 strongly supported the new theory of plate
tectonics. Thrinaxodon, a small weasel sized synapsid carnivore that was morphologically close to being
a mammal, is also known from the Early Triassic of Antarctica. In addition to other synapsids, nonsynapsid components of this fauna, include a small primitive anapsid reptile, Procolophon, and primitive
archosaurian reptiles. Small temnospondyl amphibians round out the faunal list for the Early Triassic,
which is the best known of the three Mesozoic faunas from the Transantarctic Mountains.
The Middle Triassic fauna is represented by more fragmentary material than the Early Triassic
assemblage due to the high energy depositional environment in which the bones occur, so generic
placement of many of the specimens is not possible. However, we can identify the major groups in the
assemblage. It again contains a number of synapsids (they were the dominant group of tetrapods
during much of the Triassic) however, on average they were much larger animals than the synapsids of
the Early Triassic. A large herbivorous bull sized kannemeyerid and the wolf-sized carnivore;
Cynognathus are among the synapsids from the Middle Triassic. Also included is an odd gomphodont
synapsid, with large canines but more complex post-canine teeth for grinding up plants. Perhaps the
strangest Middle Triassic animals from the fauna are the very large temonospondyl amphibians. These
include Paratosuchus, a genus known from other southern continents, and a new genus and species
Kryostega collinsoni, which had a skull nearly a meter long and was 5-6 meters in total length.
While the Early Triassic Antarctic fauna exhibits close faunal connections to the Early Triassic of
South Africa with a number of species common to both, the Middle Triassic assemblage exhibits a
greater degree of endemism, particularly among some of the temonspondyls and the gomphodont
synapsids. This may reflect either more geographic barriers to dispersal between the two Gondwana
continents, or just as likely, the Middle Triassic taxa from Antarctica might be of a slightly different age
than similar animals from South Africa.