HYPERDIVERSITY AND THE PALEOBIOGEOGRAPHIC ORIGINS OF THE LATE CRETACEOUS CROCODYLIFORMS OF MADAGASCAR

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; KRAUSE, David W., Department of Anatomical Sciences, SUNY, Stony Brook, NY 11794.

An extremely diverse assemblage of crocodyliforms from the Upper Cretaceous Maevarano Formation of Madagascar consists of a new species of the metasuchian Araripesuchus, a new mesoeucrocodylian genus, a possible peirosaurid, a long-snouted form of uncertain affinities, a possible eusuchian, one other species of indeterminate suborder, and additional remains of the previously described species Trematochampsa oblita. Only Araripesuchus and the new genus are represented by associated remains, including nearly complete skeletons.
    To further explore the implications of the morphology of the new genus, a matrix of 110 characters was subjected to a maximum parsimony analysis. Several characters potentially diagnose a monophyletic group including the new Malagasy form, Trematochampsa, and Peirosauridae. These relationships imply a South American origin for several Malagasy crocodyliform taxa (the new genus and the possible peirosaurid). Other taxa either weakly support or fail to refute dispersal from Africa; Araripesuchus is known from the Aptian of both Brazil and Niger, and another species of Trematochampsa is known from the Lower Senonian of Niger. Until the discovery of coeval faunas from Africa, the origins of the hyperdiverse crocodyliform assemblage of the Late Cretaceous of Madagascar remain a mystery, but probably incorporate vicariant as well as Late Cretaceous immigrant components.

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