New materials of rebbachisaurid sauropods from Huincul Formation at Villa El Chocón, Neuquén: a contribution to the knowledge of the appendicular anatomy of the group

LERZO, LUCAS; JUAN IGNACIO CANALE; GALLINA, PABLO A.; APESTEGUÍA, SEBASTIÁN

san luis

Encuentro; Reunión de comunicaciones de la Asociación Paleontológica Argentina.; 2017

universidad de san luis

The Rebbachisauridae constitutes a group of medium to large sauropods recorded from bothLower and Upper Cretaceous rocks (Barremian-Turonian). Whereas much of the knowledgeon their cranial anatomy comes from the highly modified skull of Nigersaurus (Sereno et al.,1999), the axial skeleton, including light presacral vertebrae with extremely laminated neuralarches and elongated, petal-shaped neural spines, is known from several taxa. Nevertheless,the knowledge on the appendicular skeleton is scarce. New materials (MMCh PV70),including a complete left tibia and an incomplete left fibula collected in the HuinculFormation nearby El Chocón (Neuquén), permit to observe some characters for the group.The tibia is massive with its proximal end anteroposteriorly expanded and the distal endlateromedially wide. The cnemial crest is widely rounded and proximodistally extended,reaching the midlength of the tibia, as in Zapalasaurus and Limaysaurus. The cnemial fossa isdeep and as length as the cnemial crest, unlike the shorter one present in Flagellicaudata. Inlateral view, a slightly posterior bulge is present on the distal third, as observed inLimaysaurus and Zapalasaurus. The distal end is ovoidal and bears a narrow and deep lateralgroove, differing from the variable condition present in Flagellicaudata. The distal fibulapreserves a lateromedially expanded end with a marked astragalar process, unlike the lessdeveloped processes in Flagellicaudata. The distribution of these features withinDiplodocoidea may represent synapomorphies for Rebbachisauridae. The inclusion of theseappendicular characters in future cladistic analysis may contribute to achieve a betterresolution of the in-group relationship. Project funded by NGS (to S.A.) and Municipalidad Villa El Chocón.