CETACEAN TEETH FROM THE LATE OLIGOCENE SAN GREGORIO AND EL CIEN FORMATIONS, BAJA CALIFORNIA SUR, MEXICO

Isolated cetacean teeth have been found in the late Oligocene (Chattian) strata in areas north and northwest of La Paz, Baja California Sur. Teeth found at the El Malabar locality, near La Purisima, are from the basal conglomerate of the San Gregorio Formation; those from Cerro Colorado and San Hilario (near El Cien), and El Saladito and Mesa Tobias (north of San Juan de la Costa) were found in phosphate beds of the El Cien Formation. Some of the teeth are complete, both caniniform and molariform, and some molariform teeth have double fused roots while others have separated double roots. The lateromedially inflated teeth are probably referable to primitive Odontoceti; those that are lateromedially flattened with widely splayed denticles are probably those of archaic Mysticeti. Primitive odontocetes and mysticetes have been previously reported from the El Cien Formation, but this is the first unequivocal record of cetaceans from the San Gregorio Formation.