Reevaluation of the holotype of Plesiosaurus (Polyptychodon) mexicanus Wieland, 1910 from the ?Upper Jurassic of Mexico: a thalattosuchian, not a sauropterygian

  • Marie-Céline Buchy Museo del Desierto, Prolongación Pérez Treviño 3745, Centro Metropolitano Parque Las Maravillas, 25015 Saltillo, Coahuila, Mexico.
Keywords: Thalattosuchia, Metriorhynchinae, Late Jurassic, Early Cretaceous, Mexico.


The holotype of the first sauropterygian described from Mexico, Plesiosaurus mexicanus Wieland, 1910, was recently rediscovered and is here described and discussed for the first time in almost a century. The holotype specimen belongs to an indeterminate metriorhynchine crocodyliform. Doubts remain as to the stratigraphic origin of the specimen, whether Upper Jurassic or Lower Cretaceous. It adds a specimen to the recently recognised wealth of the Mexican Gulf in thalattosuchians.