Tetrapod Fauna

The rocks of the Beacon Snpergronp of Gondwana are noteworthy becanse they were deposited on land rather than in the coastal ocean of Gondwana. hi addition, the sediment was deposited after plants and animals had made the transition from the ocean to life on land. Even more fortunate is the fact that the rocks of the Beacon Supergroup have preserved a record of the evolution of air-breathing tetrapods because the sediment that was deposited on alluvial plains was not removed by erosion even before it was lithified. For these reasons, the sedimentary rocks of the Beacon Supergroup can provide information that is not available in rocks that were deposited in the oceans at the same time. 

When the siltstones of the Aztec Formation were deposited during the Late Devonian, fish already existed in the rivers and lakes of Gondwana. The recovery of fossihzed fish in the Boomerang Range of southern Victoria Land was described in Section 10.1.2 (White 1968 McKelvey et al. 1972 McPherson 1978 Grande and Eastman 1986 Young 1987). 

We now turn to the fossihzed bones of amphibians and reptiles that have been found in the Early Triassic Fremouw Eormation of the central Transantarctic Mountains. The Eremouw basin was inhabited by a variety of tetrapods including labyrinthodont amphibians and therapsid reptiles which are believed to be the Triassic ancestors of Cretaceous mammals (Colbert 1949). These animals were widely distributed in East Antarctica and on the other continents of the southern hemisphere that once were part of Gondwana (Hammer 1990). Therefore, the presence of these vertebrates in 

---