The Mahajanga Basin Project: Late Cretaceous Vertebrates from Madagascar and Their Implications for the Biogeographic History of Gondwana

点击翻译按钮获取中文摘要

The face of the Earth changed radically during the Late Jurassic and Cretaceous. It is during this interval that the southern supercontinent Gondwana fragmented into isolated landmasses, with dramatic consequences for the associated terrestrial and freshwater vertebrate (backboned) animals. Reconstructions of the timing and sequence of this fragmentation are based almost entirely on geophysical evidence and remain poorly tested on the basis of terrestrial and freshwater vertebrate fossils. This proposal seeks to continue and expand a project designed to discover vertebrate fossils in Upper Cretaceous strata (approximately 65 million years old) of the Mahajanga Basin in northwestern Madagascar, to place them in phylogenetic, stratigraphic, and sedimentologic context, and to employ them in testing biogeographic and plate tectonic hypotheses relating to Gondwana as a whole and Madagascar in particular. The Mahajanga Basin Project was initiated over a decade ago but is only beginning to reach its potential. To date, PIs have quintupled the previously known species diversity of Late Cretaceous vertebrates from the island and have discovered some of the most complete and spectacularly preserved specimens of Late Cretaceous vertebrates from the southern hemisphere and, indeed, the world. But sampling is clearly incomplete and much remains to be done in the vast expanses of paleontologically and geologically unexplored Cretaceous rocks of the Mahajanga Basin. With continued work, PIs are confident that the vertebrate fauna from the Cretaceous of the Mahajanga Basin will become one of the best sampled and best known faunas of Cretaceous age from the southern hemisphere and one of the primary standards against which other Gondwanan faunas of Cretaceous age are compared. The discovery and rigorous phylogenetic analysis of additional and more complete vertebrate fossils from Upper Cretaceous horizons in the Mahajanga Basin of northwestern Madagascar, and their placement in geological context, will: 1) shed significant new light on the diversity and evolutionary history of vertebrates from the southern supercontinent of Gondwana in general and Madagascar in particular, and 2) permit tests of competing hypotheses about the physical and biotic connections of the component parts of Gondwana during the Mesozoic and serve to elucidate the biogeographic origins of the highly endemic extant vertebrate fauna of Madagascar, arguably one of the greatest unsolved mysteries of natural history. As in the past, this project is firmly committed to providing a training ground for both Malagasy graduate students and for American high school, undergraduate, and graduate students, as well as postdoctoral associates. Also as in the past, results of this project will be disseminated to both the scientific community and the general public in a variety of ways including original publication, media exposure, the internet, museum displays, and lectures/seminars. PIs will also continue their efforts to build schools and provide healthcare for children living in remote areas of Madagascar through an organization, the Madagascar Ankizy Fund (www.ankizy.org), that they established in 1998.