TITHONIAN (LATE JURASSIC) MARINE REPTILES FROM THE NEUQUEN

FERNÁNDEZ,M.; Z. GASPARINI & M. DE LA FUENTE

Bristol, Inglaterra

Congreso; 69th Annual Meeting Society of Vertebrate Paleontology; 2009

As part of a research program of Mesozoic marine reptiles of South America, more than thirty years of prospecting in Tithonian sediments of the Vaca Muerta Formation (Neuquén Basin, Northwest Patagonia, Argentina) has resulted in the discovery of a rich assemblage including ichthyosaurs, pliosaurs, metriorhynchid crocodyliforms, and turtles. Ichthyosaurs are represented by Caypullisaurus bonapartei and two new ophthalmosaurid taxa. Pliosaurids are represented by Pliosaurus; no elasmosaurid taxa have been documented. Turtles are represented by the pleurodire Notoemys laticentralis and the cryptodire Eurysternum neuquina. Metriorhynchid crocodyliforms comprise two taxa representing both morphological extremes of the clade’s diversity: the bizarre top predator Dakosaurus andiniensis, and the relatively gracile Geosaurus araucanensis. Fossils from the Vaca Muerta Formation are frequently articulated and some exceptionally preserved metriorhynchid remains include internal natural casts of the snout. The great diversity of finds in the Neuquén Basin are significant in that they fill an important paleobiogeographic gap in our understanding of Tithonian-aged marine vertebrates and are crucial for comparisons with age-equivalent assemblages such as those recently found in the Norwegian archipelago of Svalbard. From a taphonomic standpoint, morphological information provided by exceptionally preserved metriorhynchids, such as internal natural casts of the snout, allow for better understanding of soft anatomy details and bring important insights into the key innovations leading to the unparalleled marine specialization of metriorhynchids among archosaurs.