New morphological information of Buitreraptor gonzalezorum (Theropoda, Paraves) provided by a new specimen from La Buitrera fossil site (Cenomanian), Patagonia, Argentina

FEDERICO A. GIANECHINI; PETER J. MAKOVICKY; SEBASTIÁN APESTEGUÍA

Congreso; Reunión de Comunicaciones de la Asociación Paleontológica Argentina; 2019

Buitreraptor gonzalezorum Makovicky, Apesteguía and Agnolín 2005 is one of the best known Gondwanan Mesozoic paravian theropods, represented by several specimens, most of them collected from the La Buitrera fossiliferous area. Buitreraptor gonzalezorum is a member of the Unenlagiinae, often recognized as a subfamily within Dromaeosauridae. Until now, only the holotype preserves a skull, which exhibits both autapomorphic character-states and traits shared with other unenlagiines and dromaeosaurids. A newly discovered specimen (MPCA PV 627), with cranial remains and a fragmentary axis and probable atlas provides additional important morphological information for the species. MPCA PV 627 consists of a fragmentary but articulated posterior part of a skull, including the right jugal, postorbital, squamosal and quadrate; partial frontals and parietals; fragmentary braincase; right pterygoid and ectopterygoid; and mandibular bones, including right and left prearticulars and fragmentary right surangular. It also includes a natural endocast of the brain. Among the most remarkable characters not preserved in the holotype are: a prominent quadratojugal ramus of the jugal; posteriorly extended squamosal ramus of the postorbital, which surpasses the mandibular articulation of the quadrate; squamosal with posterolateral shelf overhanging the ventral ramus; quadrate markedly inclined anteroventrally, with its ventral end almost reaching the level of the main body of the postorbital; pendulous paroccipital processes; and a pleurocoel on the axis centrum. This new information augments the diagnosis of B. gonzalezorum by recognizing new autapomorphies for this taxon, thus contributing to the knowledge of the cranial anatomy of unenlagiines.