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.