Massetognathus (Cynodontia, Traversodontidae) from the Santa Maria Formation of Brazil

Abstract

Based on a new examination of published specimens and some unstudied specimens from Brazil, Massetognathus ochagaviae is re-evaluated and the diagnosis revised. One distinguished character of this species not previously mentioned is the base lateral to the labial margin of upper postcanines extending outward to form an isosceles triangle in occlusal view. It also differentiates from Massetognathus pascuali by having a higher skull and mandible, slightly dorsally pointed dentary ventral border under the coronoid process, less variable number of postcanines, nearly triangular basin on the upper canines due to the short lingual ridge, robust lower canines, and subrectangular shaped lower postcanines. The ontogenetic variation within Massetognathus ochagaviae is discussed and compared with M. pascuali. All Brazilian specimens of Massetognathus other than MCP 3284PV are referred to as M. ochagaviae. The specimen MCP 3871PV is designated as neotype for Massetognathus ochagaviae.