A new concentration lagerstätte for marine vertebrates of Tithonian (Uppermost Jurassic) age in southern Coahuila, Mexico

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In the Sierra de Jabalí, near the village of Gomez Farías, about 70 km south of Saltillo (Coahuila), we recently discovered a locality where remnants of marine reptiles of ?Early Tithonian age are concentrated in coquina layers with a thickness of about 1.5 m. The coquina unit is present in the lower third of the La Casita/La Caja Formation (Kimmeridgian to early Berriasian) and almost entirely consists of fossils cemented together by spar cement. Ammonoids, ostreid bivalves, belemnites and wood occur frequently, as well as an abundant and diverse assemblage of marine vertebrates. So far, we identified pliosaurs, plesiosaurs, ichthyosaurs, thalattosuchian crocodilians and two species of fishes. The material comprises isolated bones as well as partial and sub-complete skeletons. The concentration of vertebrates in this unit is outstanding and may have resulted from upwelling conditions near the shelf edge, widespread eutrophication and anoxia in seafloor and bottom water. It is our main objective to highlight the enormous potential of this new concentration deposit, secure further specimens and present a taxonomic inventory of the fossil assemblage with special reference to taphonomy and biostratigraphy. We further intend to precisely reconstruct the palaeoenvironmental conditions that led to the remarkable fossil concentration at Gomez Farías.