A new shartegosuchid crocodyliform from the Upper Jurassic Morrison Formation of western Colorado


E-mail: jclark@gwu.edu


A small new basal crocodyliform, Fruitachampsa callisoni gen. nov., sp. nov., is represented by several partial skeletons from the Morrison Formation at the Fruita Paleontological Area near Grand Junction, Colorado. It is placed in the Family Shartegosuchidae Efimov, 1988, previously comprising three genera from the Late Jurassic locality of Shar Teeg in western Mongolia and possibly a fourth genus from the Early Cretaceous of Siberia. Shartegosuchids share a sculpted palatal surface of the pterygoids, the absence of a mandibular fenestra, and posterior maxillary teeth and post-caniniform dentary teeth with a flat and horizontal apical region and vertical crenulations extending basally from it. Fruitachampsa and Shartegosuchus form a clade supported by ventral half of the lacrimal tapering ventroposteriorly, sculpturing on palatines, and lower teeth absent anterior to caniniforms. The shartegosuchids are most parsimoniously considered to be outside of the mesoeucrocodylian clade and are possibly allied with the Asian taxa Shantungosuchus, Sichuanosuchus, and Zosuchus. Fruitachampsa is unusual in possessing a series of small protuberances along the occipital margin of the parietal and squamosal and procoelous vertebrae, and lacking an antorbital fenestra or fossa. This is the first occurrence of a shartegosuchid in North America, and the close relationship of Fruitachampsa with Shartegosuchus nested among other Asian taxa indicates it dispersed to North America from Asia.

© 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 163, S152–S172.