Buchy M.-C. (2008) Reevaluation of the holotype of Plesiosaurus (Polyptychodon) mexicanus Wieland, 1910 from the ?Upper Jurassic of Mexico: a thalattosuchian, not a sauropterygian // Revista Mexicana de Ciencias Geológicas, v. 25, núm. 3, p. 517-522.
pdf: http://satori.geociencias.unam.mx/25-3/ (10)Buchy.pdf
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.