HOPE AND DESPAIR IN SONORA; THE LOWER AND "MIDDLE" CRETACEOUS VERTEBRATE RECORD OF MEXICO

Several localities in north-central Sonora, Mexico exposing Aptian through Cenomanian strata were intensively prospected for fossil vertebrates. A small accumulation of bone float (N 30º 11’ 4.3”, W 110º 40’ 23.3”) was located in a massive siltstone of the lower part of the Cerro La Ceja Member of the Mural Limestone (Aptian-Albian), near the small village of Tuape. While preservation is fairly good, the pieces are fragmentary making taxonomic identification impossible below the level of Vertebrata indet., though the material may well be of a large, marine reptile. Identifiable skeletal pieces include a partial vertebral centrum, possible proximal humerus, and several fragments of long bones. We report here the first occurrence of vertebrate material from the Lower Cretaceous of Mexico.

Two localities exposing the Cintura Formation (Cenomanian) near Tuape and Cabullona were also prospected. No bone material was recovered. However, at the Cabullona locality, a putative theropod footprint (N 31º 09’ 10.1”, W 109º 27’ 51.5”) was discovered as well as fossil wood.