Details of a new skull and articulated cervical column of Dinilysia patagonica Woodward, 1901

Abstract

ABSTRACT Aspects of the cranial and postcranial anatomy are presented for a new specimen of the Upper Cretaceous Gondwanan snake, Dinilysia patagonica Woodward, 1901, collected near Paso Cordoba, Rio Negro Province, Argentina, during the field season of 2001. The specimen preserves important features of the dentary and postdentary bones (in particular the coronoid and compound bone), the quadrate, and the ventral surface of the basicranium, as well as the axis, atlas, and anteriormost cervical vertebrae. The third and fourth cervicals are preserved with unfused and articulating intercentra on large, ovate, concave hypapophyses (typical of dolichosaurs, mosasaurs, adriosaurs, etc.), while the inter-centrum of the fifth appears to be fused to a long, narrow hypapophysis (this latter condition is typical of modern snakes). These new data influence the construction of primary homology statements used in cladistic analyses of squamate phylogeny generally and ophidian phylogeny specifically. Comparison of the cranial anatomy of Dinilysia to that available for the recently described Argentine Gondwanan snake, Najash rionegrina Apesteguía and Zaher, 2006, indicates important similarities in the two species to the exclusion of scolecophidian snakes.