PALEOBIOGEOGRAPHIC SIGNIFICANCE OF CRETACEOUS CONTINENTAL VERTEBRATES FROM ANTARCTICA AND AUSTRALIA

The Cretaceous witnessed the fragmentation of Gondwana and the resultant origins of most modern southern continents. Nevertheless, the timing and sequence of events in Gondwanan breakup, as well as their consequences for the evolution and distribution of freshwater and terrestrial vertebrates, have been the subject of intense debate in recent years. At least four large-scale paleobiogeographic hypotheses relating to Gondwanan fragmentation have been proposed. Because each of these hypotheses makes different predictions regarding the affinities of biotas on specific landmasses through successive Cretaceous stages, it should be possible to test them by deciphering the evolutionary relationships of continental vertebrates that inhabited the Southern Hemisphere during these times. Regrettably, however, this has not yet been possible, due in large part to the paucity of phylogenetically informative fossils of Cretaceous freshwater and terrestrial vertebrates from Antarctica and Australia.

Ongoing research efforts are enhancing our understanding of Cretaceous vertebrates from these austral continents. Coupled with continued paleontological explorations, studies of undescribed Late Cretaceous non-avian dinosaur and bird material from the Antarctic Peninsula promise to yield important new revelations on Antarctic faunas. Similarly, analyses of newly-discovered, exquisitely-preserved fossils from the Albian-Cenomanian of Queensland are providing unprecedented insight into the paleobiogeographic relationships of Australian mid-Cretaceous freshwater and terrestrial vertebrates. When integrated with other relevant paleogeographic and paleontological data, and analyzed using rigorous paleobiogeographic methods, these discoveries will bring us closer to a comprehensive assessment of the nature of the Cretaceous continental vertebrate faunas of Antarctica and Australia and their significance for the evolution and distribution of Gondwanan biotas.