Is the frontoparietal foramen present in rebbachisaurid sauropods? new materials from patagonia shed light on this anatomical feature

LUCAS LERZO; PABLO A. GALLINA; ALEJANDRO OTERO; JUAN CANALE

Jornada; 34 Jornadas Argentinas de Peleontología de Vertebrados; 2021

The Rebbachisauridae constitutes a group of small (9 m-long) to medium (around 15 m-long) sauropods recorded from Barremian to Turonian (Lower to Upper Cretaceous). In the last two decades, the knowledge about the anatomy of Rebbachisauridae has increased, although skull remains are frequently incomplete and poorly known; out of 17 species around the world, only four taxa preserved cranial remains (Limaysaurus, Nigersaurus, Lavocatisaurus and MMCh-PV 71). Except for Lavocatisaurus, remaining rebbachisaurids preserved the neurocranium and would seem to share the absence of a frontoparietal foramen, which is also known as ?pineal?, ?postfrontal?, ?parietal?, ?interfrontal foramen? or ?frontoparietal fenestra?. The presence of this opening is usually considered as a synapomorphy of Dicraeosauridae and, outside this family, it is also present in Apatosaurus (BYU-17096) and the basal sauropod Spinophorosaurus. Skull roof materials of an adult rebbachisaurid (MMCh-PV 70) from Huincul Formation, collected near Villa El Chocón, present a conspicuous frontoparietal foramen. The preserved fused frontals exhibit the anterior margin of this foramen. After a careful examination, this feature is also recognized in the rebbachisaurid specimen MMCh-PV 71, although not mentioned in its original description. While some authors hypothesized that this foramen is related to the parietal-pineal complex of the forebrain, others considered this structure related to ontogeny and present in young individuals. This novel evidence indicates that this frontoparietal foramen is present in some adult specimens of Rebbachisauridae and shows a wider distribution within Diplodocoidea, with a clear potential as a morphological character to analyze in future phylogenetic studies of this group.ISOTOPIC