Osteology of aristonectes quiriquinensis (elasmosauridae, aristonectinae) from the upper maastrichtian of central Chile

Abstract

The upper Maastrichtian elasmosaurid plesiosaur Aristonectes quiriquinensis from central Chile is here redescribed following further preparation of the holotype. New cranial characters include a flattened skull with a caudal extension of the mandibular articulation far posterior to the occipital condyle; a very long, horizontal, and posteriorly oriented paroccipital process; mandible with restricted gape angle; and teeth oriented rostrally and not interlocking during occlusion. Postcranial features include the presence of very long extremities (ca. 3 m), whereas features of the caudal-most vertebrae suggest the presence of a horizontal caudal fin. Additionally, neuroanatomical features of Aristonectes are for the first time described based on a braincase cast. Integration of osteological features, anatomical comparisons, as well as taphonomic and environmental data strongly suggests that the foraging behavior of Aristonectes quiriquinensis incorporated a mix of engulfment and feeding from benthic sediments. This is a novelty among elasmosaurids, so far considered as mainly epipelagic feeders.