A new crocodyliform from Zos Canyon, Mongolia. American Museum novitates ; no. 3445

Abstract

Here we report on a new fossil crocodyliform from Cretaceous Redbeds in the Zos Canyon, Gobi Desert, Mongolia. This new taxon, Zosuchus davidsoni, is described based on the information provided by five specimens collected during expeditions of the Mongolian Academy of Sciences-American Museum of Natural History. Zosuchus davidsoni is identifiable by numerous characters, including a posteriorly extensive secondary palate that opens through a secondary choana bordered by the palatines and pterygoids near the posterior edge of the skull, and a lacrimal-premaxillary contact on the dorsal surface of the snout. The phylogenetic relationships of Zosuchus davidsoni are shown through a parsimony analysis in the context of Crocodyliformes. This new form is found to be a late-appearing basal crocodyliform, forming a monophyletic group with two other taxa from the early Cretaceous of China. Because of the basal position of Zosuchus within Crocodyliformes, the marked posterior extension of the secondary palate is most parsimoniously interpreted as a convergence with the derived condition of neosuchian crocodyliforms.