A Middle Jurassic Sphenodon-like sphenodontian (Diapsida: Lepidosauria) from Huizachal Canyon, Tamaulipas, Mexico

A new Middle Jurassic North American sphenodontian, Cynosphenodon huizachalensis, gen. et sp. nov. is described on the basis of several dentaries and maxillae. It is characterized by its small size and its striking similarity to Sphenodon. The presence of a deep posteromedial wear facet on the caniniform tooth, a small denticle in the additional tooth series, and an anterior small groove dorsal and convergent to the Meckelian Canal, are unique characteristics of this species. In adult individuals the caniniform tooth placed posteriorly to an edentulous ridge, and the presence of wear facets on teeth and jaws caused by propalinal jaw action, suggest that C. huizachalensis is closely related to Sphenodon; the wear facet on the posteromedial face of the caniniform tooth, however, may suggest a different arrangement of the anterior palatal region.