The bivalve Odontogryphea thirsae, formerly “Ostrea thirsae,” is restricted to the Nanafalia Formation and is extensively used as a biostratigraphic zonal indicator in the Paleocene of the southeastern and central United States. Toulmin (1977) noted that O. thirsae was reported from the Tuscahoma Sand in early publications but stated (p. 191), “Reports of occurrence in the Tuscahoma Sand are probably in error.”