A new polycotylid plesiosaur with extensive soft tissue preservation from the early Late Cretaceous of northeast Mexico

"A nearly complete skeleton of a poly - cotylid plesiosaur is described from the early Late Cretaceous laminat- ed limestones at Vallecillo, northeast Mexico. It shows extensive soft tissue preservation. In some exceedingly well preserved areas there are trans- versely elongate rectangular to trap - ezoid millimetric scale-like structures arranged in longitudinal rows. The trailing edge skin flap preserves fibers and scale rows perpendicular to the trailing edge. A thick layer of subder - mal tissue is present, especially along the tail base. It was responsible for the hydrodynamic drop-shaped body contour, with the body and tail form - ing a single unit. The body shape determined from the preserved soft tissues suggests a swimming speed similar to extant leatherback turtles. Based on the unique osteology of the palate, which is intermediate between Dolichorhynchops and Trinacromerum , and according to the unique mor - phology of the girdles and propodi- als as well as the medially converging gastralia, the new specimen is placed in a new genus and species of Poly - cotylidae, Mauriciosaurus fernandezi gen. et sp. nov."