The streptoneuran gastropods, exclusive of the Stenoglossa, Ptenoglossa, and Heterostropha, of the Coffee Sand (Campanian) of northeastern Mississippi
Description
A recently discovered fossiliferous zone, the Chapelville fossiliferous horizon, in the Tupelo Tongue of the Coffee Sand in northern Lee County, Mississippi, contains the best preserved and most diverse molluscan fauna known from the Campanian Stage (Late Cretaceous). This fauna contains about three hundred molluscan species and is comparable in both preservation and diversity to the well known Maastrichtian fauna of the Coon Creek Tongue of the Ripley Formation at Coon Creek in McNairy County, Tennessee. Twenty-two families, forty genera, and fifty-seven species of streptoneuran gastropods (exclusive of the Stenoglossa, Ptenoglossa, and Heterostropha) are recognized and are illustrated in a series of 22 plates. Five species of archaeogastropods are described; two of which are new. The Caenogastropoda, exclusive of the Strenoglossa, Ptenoglossa, and Heterostropha, include fifty-two species; twenty-five (including one subspecies) of which are new Protoconchs of several taxa are described here for the first time. Two genera, Demasia and Lemniscolittorina, which had previously been assigned to the archaeogastropoda Family Neritidae and the caenogastropod Family Littorinidae, respectively, are reassigned to the heterostroph families Amathinidae and Mathilildae based on their protoconchs The systematic section contains a new classification that incorporates parts of the recently proposed gastropod classifications of Ponder and Waren (1988) and Haszprunar (1988a, b). The Chapelville gastropoda fauna of the Tupelo Tongue provides a window into the pre-Maastrichtian streptoneuran diversity of the northern U.S. Gulf region. It contains the earliest geologic record of many Cenozoic taxa and is surprisingly modern in many respects