Morphology, relationships, and biogeographical significance of an extinct horned crocodile (Crocodylia, Crocodylidae) from the Quaternary of Madagascar

Abstract

Phylogenetic analysis indicates that Crocodylus robustus Grandidier & Vaillant, 1872 is more closely related to the living African dwarf crocodiles (Osteolaemus) than to living Crocodylus. The type series cannot be identified, but the original description includes details consistent with known specimens that almost certainly pertain to the same species. It had a prominent triangular 'horn' on the posterolateral corner of each squamosal; near-exclusion of the nasals from the external naris; constricted supratemporal fenestral rims; a dorsoventrally deep snout; a constricted external mandibular fenestra in which the surangular-angular suture emerges from the posterior rather than posteroventral margin; and robust limb and limb girdle elements. It shares with Osteolaemus, and with several extinct crocodylids from the Neogene of Africa, a depressed surface of the pterygoid around the internal choana forming a choanal 'neck'. It cannot be referred to Crocodylus and a new praenomen, Voay, is established for its reception. Voay persisted into the Holocene and may have been extant when humans first settled Madagascar 2000 years ago, when it may have been a casualty of a megafaunal extinction event on the island. This is consistent with molecular data that suggest comparatively recent dispersal of Crocodylus niloticus to Madagascar from mainland Africa. © 2007 The Linnean Society of London.