A new gobiosuchid crocodyliform from the Cretaceous of Mongolia

POL, D.; NORELL, M.A.

AMERICAN MUSEUM NOVITATES

American Museum of Natural History

Lugar: New York; Año: 2004 vol. 3458 p. 1 - 31

0003-0082

We describe a new fossil crocodyliform, Zaraasuchus shepardi, found in the Cretaceous Red Beds of Zos Canyon (Gobi Desert, Mongolia). Z. shepardi shares numerous derived characters with Gobiosuchus kielanae, also known from the Late Cretaceous of Mongolia (Bayn Dzak locality). However, it is distinguished from the latter by the presence of a moderately large infratemporal fenestra, anterior margin of infratemporal fenestra almost completely formed by the postorbital, retroarticular process with a well developed ornamented posterolateral pointed process, and extremely well developed keels on dorsal and lateral cervical osteoderms (the height of which is approximately as long as the lateromedial extension of the dorsal osteoderms). A phylogenetic analysis indicated that these two taxa form a monophyletic group located basally among crocodyliforms. This clade is diagnosed by fourteen synapomorphies (e.g., anterior and posterior palpebrals sutured to each other and to the frontal, excluding it from the orbital margin, external surface of ascending process of jugal exposed posterolaterally, dorsal surface of posterolateral process of squamosal ornamented with three longitudinal ridges, dorsal surface of osteoderms ornamented with anterolaterally and anteromedially directed ridges, cervical region surrounded by lateral and ventral osteoderms sutured to the dorsal elements, and closed supratemporal fenestra).