NEW MATERIAL FROM NORTH AMERICA DIVERSIFIES THE LAURASIAN RHYNCHOSAUR RECORD

Rhynchosaurs are a group of terrestrial archosauromorphs possessing characteristically derived jaw anatomy consisting of multiple tooth rows per jaw and a prominent premaxillary beak. Rhynchosaur fossils are common throughout many Middle & Upper Triassic deposits of the southern, formerly-Gondwanan continents, namely South America, Africa, and India. Laurasian deposits rarely possess material of rhynchosaurs; the only abundent rhynchosaur assemblages among the northern continents are found in the Middle & Upper Triassic strata of England and Scotland. Any new rhynchosaur specimens from Laurasia thus represent an important aspect of our understanding of Triassic vertebrate biogeography. Here we describe a collection of new and previously-collected rhynchosaur elements from the Jelm Formation in Wyoming, USA, and the Evangeline Member of the Wolfville Formation in Nova Scotia, Canada. The previously-collected specimens are notable in that they have all been previously referred to the multispecific genus Hyperodapedon and have been used to support Hyperodapedon as a cosmopolitan genus and a vertebrate biochron of the Adamanian-Otischalkian (Carnian). We include all of this material in a phylogenetic analysis to assess these previous phylogenetic hypotheses and to examine the affinities of these specimens within Rhynchosauria. Our results find the material to be from non-Hyperodapedon hyperodapedontines, primarily due to the lack of lingual teeth on the dentaries and the presence of a single longitudinal groove but a small number of maxillary tooth rows. Though the material is too fragmentary for generic referral, its distinction from Hyperodapedon and other rhynchosaurs expands known rhynchosaur diversity and demonstrates the weakness of the Hyperodapedon biochron.