pdf: http://digbib.ubka.uni-karlsruhe.de/volltexte/documents/21575

The result of six years of examination of marine reptiles from north-east Mexico is presented here. The area yielded specimens from both the Late Jurassic and Late Cretaceous. For a region where few, undescribed forms were known, the process yielded several new taxa, and a variety of forms, most of which await preparation, composing rich, hitherto non documented assemblages. At present the assemblage of Late Jurassic Mexican Gulf marine reptiles comprises pliosaurs, thalattosuchians, ichthyosaurs and few plesiosaur remains; no turtle remain was discovered yet. All proceed from the La Caja / La Casita / La Pimienta Formations (Kimmeridgian to Tithonian). Except for the ubiquitous ichthyosaur Ophthalmosaurus icenicus, many specimens, even uncomplete, differ from coeval forms and appear to confirm the partial isolation of the area that was previously deduced from invertebrates and microfossils. During the Cretaceous, the Mexican Gulf connects to both the Western Interior Seaway and the Atlantic Ocean. Late Cretaceous marine reptiles from north-east Mexico come from the Late Turonian to early Coniacian Austin Group at Múzquiz, Coahuila, a promising locality from where few specimens are available for study at present; the Campanian-Maastrichtian Méndez Formation in Nuevo León yielded few mosasaurid occurrences; most specimens at present proceed from the Early Turonian Agua Nueva Formation at Vallecillo, Nuevo León. From Vallecillo is known the only pliosaur remain from the Mexican Late Cretaceous, a partial tooth attributed to Polyptychodon, and several basal mosasauroids. These were discovered recently and no taxonomical frame is available at present, but preservation is usually excellent, including soft parts, and it is expected their study will greatly increase our knowledge of the group.