New abelisaurid skeletal remains from La Invernada (Bajo de la Carpa Formation, Santonian), northwestern Patagonia, Argentina

GIANECHINI, FEDERICO ABEL; MÉNDEZ, ARIEL HERNÁN; FILIPPI, LEONARDO SEBASTIÁN; JUÁREZ VALIERI, RUBÉN D.

Otro; 1º Reunión Virtual de Comunicaciones de la Asociación Paleontológica Argentina; 2020

The La invernada fossil area (Bajo de la Carpa Formation, Santonian) has provided abundant dinosaur remains, which are mainly represented by titanosauriform sauropods and abelisaurid theropods. The latter include Viavenator exxoni and other partial skeletons. Recently a new abelisaurid specimen (MAu-Pv-Li-665) was found in La invernada, which consists of three vertebrae (anterior cervical, cervico-dorsal and dorsal) and cervical and dorsal ribs, found closely associated. The centrum and neural arch of the anterior cervical are unfused. The centrum shows a pleurocoel posteriorly located and a ventral keel, resembling anterior cervicals of Viavenator, although it differs from those by a less dorsoventral compression and a less concave posterior articular surface. The cervico-dorsal vertebra has small epipophyses and two pleurocoels, as the tenth cervical of Viavenator, although it differs from that by more laterally projected diapophyses and the absence ofconvex lateral and ventral surfaces of the centrum (a proposed autapomorphy of Viavenator). The dorsal vertebra, inferred as a d3? or d4?, has a well-developed hyposphene-hypantrum articulation, profuse infradiapophyseal pneumaticity, and a single pleurocoel. Conversely, the dorsals of Viavenator do not have this type of pneumaticity, and have two pleurocoels, except the second one, which has one. The ribs show pneumatic foramina, as in other abelisaurids, and differently to Viavenator the dorsal ribs have more developed cranial intercostal ridges. The mentioned differences preclude refer the specimen to V. exxoni and is considered as an indeterminate Abelisauridae, probably a furileusaurian. This finding demonstrates the remarkable abundance and diversity of abelisaurid remains from La Invernada.