CAMPANIAN (UPPER CRETACEOUS) CROCODYLIFORMS FROM MADAGASCAR AND THEIR BIOGEOGRAPHIC IMPLICATION

BUCKLEY, Gregory A., Department of Geology, Field Museum of Natural History, Chicago IL 60605; BROCHU, Christopher A., Department of Geological Sciences, University of Texas at Austin, Austin TX 78712.

Recent expeditions to the Mahajanga Basin of northwestern Madagascar have resulted in the discovery of several species of crocodyliforms in the terrestrial Campanian deposits of the Maevarano Formation. These taxa offer important clues in discerning the biogeographic history of the Mesozoic Malagasy biota.
    The discoveries include four loosely articulated skeletons of the metasuchian Araripesuchus. Like other members of this taxon, the Malagasy form is small at maturity (approximate skull length 80 mm) and possesses a short snout with large orbit, a large antorbital fenestra, a robust internarial bar, and very gracile limb elements. A second discovery was a partial skeleton of Trematochampsa oblita, previously known from the area by several dentary fragments. Postcranial material is remarkably well preserved, which is important in that trematochampsids as a whole are very poorly known. These specimens will no doubt help resolve relationships at the base of the Metasuchia.
    The presence of Araripesuchus (known only from the Aptian of Brazil and Niger) and Trematochampsa (known only from the early Senonian of Niger) in the Campanian Malagasy fauna is interesting, because Madagascar is understood to have separated from mainland Africa during the Mid- to Late Jurassic. Although dispersal of taxa to Madagascar during the late Early to Late Cretaceous is the most feasible hypothesis, the exact dispersal route is still unknown.

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