Occurrence of a second ichthyosaur genus (Reptilia: Ichthyosauria) in the Late Jurassic Gulf of Mexico

摘要

The forefin of the recently excavated partial skeleton of a large ichthyosaur is here described. The specimen comes from the upper Tithonian (Upper Jurassic) La Caja Formation in the south of Coahuila State. The anatomy of the forefin as well as of those currently visible parts of the skull demonstrates it likely represents an Ophthalmosauridae, in any case it is distinct from Ophthalmosaurus, possibly close to Brachypterygius. Although generally poorly diagnostic, Late Jurassic Mexican ichthyosaurian remains are relatively abundant; a single specimen was surely identified as belonging to Ophthalmosaurus. The new specimen is therefore the first evidence of the presence of a second ichthyosaurian genus in the Late Jurassic Mexican Gulf.