Abstract

ABSTRACT—Two previously studied specimens of Gansurhinus qingtoushanensis are restudied, accompanied by the description of a relatively complete skeleton from the Lopingian Naobaogou Formation of Nei Mongol, China. The new skeleton represents an immature individual of a new species of Gansurhinus, which can be diagnosed by the choana position posterior to the premaxillary teeth, maxillary tooth position numbers of tooth row 5 is about half of tooth row 4, and length of row 5 is much shorter than length of tooth row 4. IVPP V12026 from the Naobaogou Formation is referred to the new species. Gansurhinus is distinguished by a diastema on the upper jaw, five rows of teeth on maxilla and dentary, teeth on the multiple tooth-rowed region bearing cusp-like emargination on the crown, lacking dental tooth wear. The following features could be the diagnostic characters of the genus or autapomorphies of the new species: ectopterygoid present; adductor fossa short relative to the length of lower jaw, with small contribution of surangular toposterolateral border; trapezoidal coronoid eminence with nearly straight dorsal margin; and foramen intermandibularis caudalis absent. Gansurhinus is more closely related to Rothianiscus than Moradisaurus, supporting previous analyses. This study further confirms recent work suggesting that the moradisaurine clade is more diverse than currently recognized.