BIOGEOGRAPHIC ORIGINS OF THE NON-DINOSAURIAN VERTEBRATE FAUNA OF MADAGASCAR: NEW EVIDENCE FROM THE LATE CRETACEOUS

KRAUSE, David W., Dept. Anat. Sci., SUNY, Stony Brook NY 11794; ASHER, Robert J., Doct. Progr. Anthro. Sci., SUNY, Stony Brook NY 11794; BUCKLEY, Gregory A., Dept. Geol., Field Museum, Chicago IL 60605; GOTTFRIED, Michael D., Mich. St. Univ. Mus., East Lansing, MI, 48824; LaDUKE, Thomas C., Dept. Biol. Sci., East Stroudsburg Univ., East Stroudsburg, PA, 18301.

The developing record of fossil vertebrates from the Late Cretaceous (Maastrichtian) of Madagascar and elsewhere in Gondwana, as well as revised paleogeographic reconstructions, provide important constraints on hypotheses involving the biogeographic history of the Malagasy vertebrate fauna. The general absence of potentially ancestral representatives in the Late Cretaceous of Madagascar supports the hypothesis that the basal stocks of the extant vertebrate taxa (e.g., fishes, frogs, snakes, crocodiles, birds, mammals) arrived in post-Cretaceous times. There is no supporting geological evidence for antiquated yet recently resurrected notions of land bridge connections with Africa during the Late Cretaceous and Cenozoic. Dispersal of vertebrate taxa from or to Africa during the Late Cretaceous and Cenozoic therefore would have necessitated the crossing of a highly restrictive marine barrier, the Mozambique Channel. By contrast, several elements of the Late Cretaceous vertebrate fauna of Madagascar demonstrate affinities with contemporaneous taxa in both South America and India. This suggests an unexpectedly high degree of cosmopolitanism among Late Cretaceous Gondwanan terrestrial and freshwater vertebrate faunas, best explained paleogeographically by subaerial connections involving Antarctica.

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