Friday, March 3, 2017

[Paleontology • 2017] Mauriciosaurus fernandezi • A New Polycotylid Plesiosaur with Extensive Soft Tissue Preservation from the early Late Cretaceous of northeast Mexico

 Mauriciosaurus fernandezi
Frey, Mulder, Stinnesbeck, Rivera-Sylva, Padilla-Gutiérrez & González-González, 2017  

A nearly complete skeleton of a polycotylid plesiosaur is described from the early Late Cretaceous laminated limestones at Vallecillo, northeast Mexico. It shows extensive soft tissue preservation. In some exceedingly well preserved areas there are transversely elongate rectangular to trapezoid 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 subdermal tissue is present, especially along the tail base. It was responsible for the hydrodynamic drop-shaped body contour, with the body and tail forming 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 morphology of the girdles and propodials as well as the medially converging gastralia, the new specimen is placed in a new genus and species of Polycotylidae, Mauriciosaurus fernandezi gen. et sp. nov. 

Keywords: Vertebrate palaeontology, Plesiosauria, Polycotylidae, Late Cretaceous, northeast Mexico, soft tissue preservation, palaeoecology.

Figure 3 : Mauriciosaurus fernandezi  INAH CPC RFG 2544 P.F.1.
 A) Photograph of the specimen after preparation, B) interpretative line drawing. Note the massive tail base and the dorsal skin preserved between the ribs. 

Systematic paleontology

Plesiosauria de Blainville, 1835
Plesiosauroidea Welles, 1943
Leptocleidia Ketchum and Benson, 2010

Polycotylidae Williston, 1908

Mauriciosaurus gen. nov
Mauriciosaurus fernandezi sp. nov.

Derivation of name: Genus and species name in honor of Mauricio Fernández Garza, who not only made the specimen accessible for scientific research, but also secures all future work in the quarry area at Vallecillo and supports public education in Earth- and biological sciences predominantly in the state of Nuevo León.

Eberhard Frey, Eric W.A. Mulder, Wolfgang Stinnesbeck, Héctor E. Rivera-Sylva, José Manuel Padilla-Gutiérrez and Arturo Homero González-González. 2017. A New Polycotylid Plesiosaur with Extensive Soft Tissue Preservation from the early Late Cretaceous of northeast Mexico. Boletín de la Sociedad Geológica Mexicana. 69(1); 87–134.

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