A complete late Cretaceous iguanian (Squamata, Reptilia) from the Gobi and identification of a new iguanian clade ; American Museum novitates, no. 3584

Abstract

Iguania is a diverse clade with an incompletely known fossil record. Here, we describe and name the earliest iguanian known from a complete skeleton. The specimen (IGM 3/858) comes from Ukhaa Tolgod (Upper Cretaceous of Mongolia) and offers important insights into the evolutionary history of iguanian osteology. The new taxon is diagnosed by a combination of character states, including the presence of a frontoparietal fontanelle, absence of an enlarged nuchal fossa, and unflared tooth crowns. We performed a cladistic analysis including 54 taxa scored for 202 informative morphological characters. A strict consensus of 46 shortest recovered trees reveals that the new taxon is a basal member of a previously unidentified clade of Cretaceous iguanians, probably endemic to the Gobi. This clade of Gobi iguanians is nested within a monophyletic Pleurodonta (non-acrodontan iguanians).