Lower Cenomanian and Late Albian Ammonites, Especially Leylliceridae of Texas and Mexico

The Early Cenomanian of Texas and northern Mexico contains numerous species of lyellicerines, and the late Early Cenomanian Buda Limestone is especially dominated by them. The three lyellicerine genera are Sto- Hczkaia, Faraudiella, and Budaiceras, and the latter two are particularly abundant. The 50 species of Early Cenomanian ammonites are distributed among 28 genera, mostly hetermorphs, scaphitines, and lyellicerines. Because of Tethyan faunal affinities the Early Cenomanian of Texas and northern Mexico can be correlated more easily with that of North Africa and Madagascar than with the more classical sections of northern Europe. Unfortunately, no horizon-differentiation by fossils. The Main Street Limestone and Del Rio Clay are correctable with the Hypoturrilitas schneegansi zone of North Africa, the Buda Limestone with the lower part of Zone II and the Woodbine with the upper part of Zone 11 and most of Zone 111. The H. carcitanensis zone of England would appear to be equivalent to the upper part of the Del Rio Formation, the Mantelliceras saxbii zone mostly equivalent to the Buda Limestone, and the M. dixoni zone equivalent to the Maness Shale and the lower part of the Woodbine Formation. Lower Cenomanian strata thin onto the San Marcos Platform, the Devils River trend.