Article: A new pliosaur from the Bajocian of the Neuquen Basin, Argentina

A new pliosaur with a spatulate symphysis is described as Maresaurus coccai gen. et sp. nov. The holotype is from the upper levels of the Los Molles Formation (Lower Bajocian, Middle Jurassic) of the southern Neuquen Basin, central-western Argentina. Maresaurus coccai shares with Simolestes such synapomorphies as the absence of a dorso-medial foramen, lack of anterior interpterygoid vacuity, and fewer than 26 alveoli in the dentary. The autapomorphies of M. coccai are the strong flanges formed by the premaxillary and maxillary, the expanded and elevated pterygoid wings, a diastema between the eighth and ninth mandibular alveoli and the hypertrophied teeth (caniniforms) which are densely striated and without carinae or smooth faces. The record of Bajocian plesiosaurs is restricted to Simolestes keileni from the Upper Bajocian of France and M. coccai from the Lower Bajocian of the Neuquen Basin. The latter is associated with other marine reptiles, mainly ichthyosaurs, coeval with greater diversity in the invertebrate fauna, in an offshore deposit dominated by pelagic sedimentation.