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Keywords:

  • Archosauria;
  • Crurotarsi;
  • Crocodylomorpha;
  • crocodilians;
  • osteology;
  • skull;
  • phylogenetic

Erpetosuchus, a small archosaurian reptile from the Late Triassic of Scotland and North America, hasoften been implicated in the ancestry of crocodilians. A restudy of the type specimen, using new high-fidelity casts, as well as examinationof new, hitherto undescribed material, allows a detailed description and restoration of Erpetosuchus granti from the LossiemouthSandstone Formation (late Carnian, Late Triassic). This small reptile is known only from the front end of its body; a complete skull,cervical vertebral column, anterior dorsals and ribs, shoulder girdle, and forelimb. The skull shows a number of unusual features: a reducedrow of only 4–5 teeth on the anterior part of the maxilla, a large antorbital fenestra set in a deep fossa whose margins aremarked by distinct sharply angled ridges, a jugal that is divided into a lateral and a ventral portion by a sharp ridge, a deeplyrecessed tympanic area, the angular and surangular marked by a strong ridge running back from the ventral margin of the mandibular fenestra,and teeth oval in cross-section and lacking anterior and posterior carinae and marginal serrations. The remains suggest that Erpetosuchus wasa light, cursorial animal that may have fed on insects. A cladistic analysis of crurotarsan archosaurs indicates that Erpetosuchus isthe closest sister group of Crocodylomorpha among known basal archosaurs. It shares with them a deep recess in the cheek region framed bythe quadrate and quadratojugal which slope forward side-by-side at an angle of 45° above horizontal, and reach the uppermargin of the lower temporal fenestra. In Erpetosuchus the recess is entirely lateral, while in crocodylomorphs, the recesspenetrates medially as well, since the quadrate/quadratojugal bar meets the side wall of the braincase. © 2002The Linnean Society of London, Zoological Journal of the Linnean Society, 2002, 136, 25–47.