At El Rosario, 170 km WNW of Múzquiz in northern Coahuila, Mexico, alternating evenly layered platy limestone and . ssile marly limestone of late Turonian-early Coniacian age (Late Cretaceous) contain vertebrate fossils with exceptionally well-preserved anatomical details of their soft tissues, as well as abundant ammonoids, inoceramids and other invertebrates. Deposition was in an open marine shelf environment near the southern opening of the Western Interior Seaway, several hundreds of kilometers south of the North American coastline, in water depths of at least 50-100 m. The present research intends to highlight the enormous preservational potential of this new conservation deposit (Konservat- Lagerstätte) and to analyze the paleoenvironmental conditions present at this locality. Our preliminary data suggest that the El Rosario fossil deposit is a combined result of anoxic bottom conditions, early diagenetic phosphatization, and rapid burial in a soft, micritic lime mud.   PDF