New appendicular material of Skorpiovenator bustingorryi (Theropoda: Abelisauridae) from the Huincul Formation (Cenomanian, Upper Cretaceous), Patagonia, Argentina

CANALE, JUAN IGNACIO; CERRONI, MAURICIO ANDRÉS; BAIANO, MATTIA

La Plata

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

The abelisaurid Skorpiovenator bustingorryi Canale et al., 2009, is known by an almost complete skeleton, recovered from the lowest section of Huincul Formation (Cenomanian, Upper Cretaceous) near El Chocón town, Neuquén Province. Although both tibiae of the holotype were recovered, their proximal ends are incomplete, preventing the observation of some important characters of cnemial crest. Here we present a proximal end of a right tibia (MMCh-PV 255), which by its geographical and stratigraphical provenance, and equivalent morphology with the holotype, can be confidently assigned to Skorpiovenator. As in other abelisauroids, the cnemial crest is well developed and anterodorsally projected. Moreover, this crest shows a hatchet-shaped morphology, with a subrectangular outline in lateral view, also observed in some abelisaurids as Pycnonemosaurus Kellner and Campos, 2002, Ekrixinatosaurus Calvo et al., 2004 and Aucasaurus Coria et al., 2002. Over the mediodistal sector of the cnemial crest there is a small lateral accessory process, also observed in Aucasaurus. In proximal view the lateral condyle is much wider than the medial one, as in Aucasaurus and Xenotarsosaurus Martínez et al., 1986, and both condyles shows a subquadrangular outline, with flat posterior margins; a trait not observed in other abelisaurids, which could represent an autapomorphy of Skorpiovenator. The excellent preservation of the bone surface allows establishing clear sectors of muscular insertion; including mm. iliotibialis, femorotibialis, ambiens and gastrocnemius. Although fragmentary, this new material adds novel information about the anatomy of Skorpiovenator, allowing the recognition of a possible autapomorphy and some characters of potential phylogenetic significance.