Upper Albian and Lower Cenomanian ammonites from the Main Street Limestone, Grayson Marl and Del Rio Clay in northeast Texas

The ammonite faunas of the Main Street Limestone, Grayson Marl and Del Rio Clay form the basis for a revised upper Upper Albian to lower Lower Cenomanian zonal sequence in northeast Texas. A Mortoniceras (Subschloenbachia) rostratum Zone, previously known to be well-represented in the Denton Clay, Weno Limestone, and Pawpaw Shale, extends into the lower Main Street Limestone. A M. (S.) perinflatum Zone is also recognised in the Main Street on...