An Anilioid snake from the Upper Cretaceous of Patagonia

GÓMEZ, R.O.; BÁEZ, A.M.

Río de Janeiro

Congreso; II Congreso Latinoamericano de Paleontología de Vertebrados; 2005

Museu Nacional do Rio de Janeiro

Herein we report the first remains of anilioids from Patagonia. The fossils come from strata assigned to the lower member of the Allen Formation (Malargüe Group, Neuquén Basin), Late Campanian-Early Maastrichtian in age, at Bajo de Trapalcó and Bajo de Santa Rosa localities (Río Negro Province, Patagonia, Argentina). The material consists of a few isolated vertebrae, which represent the mid-posterior trunk region of the column. As aniilid vertebrae lack unique features, they are referred to Aniliidae s.l. on the basis of the following combination of character states: depressed vertebrae with low neural arches, reduced neural spines, strongly inclined zygapophyses, very short prezygapophysial processes, and neural arches with shallow median notches. This material differs from most aniliids, and resembles Hoffstetterella brasiliensis from the Paleocene of São José de Itaboraí (Brazil), in having a more developed neural spines and shallower interzygapophysial constrictions. However, the vertebrae reported here have neural arches with less conspicuous median notches and smaller neural canals than those of Hoffstetterella brasiliensis. Because in this case these differences cannot be attributed to intracolumnar or ontogenetic variation, they strongly suggest that these remains represent a new taxon. Only five fossil aniliid genera, all based on vertebrae, are known to date, although most Cretaceous records are attributed to Coniophis. The material from Patagonia constitutes the southernmost record of aniliids and provides evidence of their wide distribution during the late Cretaceous.