THE LATE CAMPANIAN (UPPER CRETACEOUS) CEPHALOPOD FAUNA OF THE COON CREEK FORMATION AT THE TYPE LOCALITY

There is an unusually rich, Late Campanian (Upper Cretaceous), molluscan fauna from the Coon Creek Formation at its type locality, 7 1/2 miles north of Adamsville, McNairy County, Tennessee. The ammonite fauna is a typical, late Campanian, Gulf Coast fauna consisting almost entirely of aberrant ammonites and only one tightly coiled, planispiral form. A few authors have published on the fauna from this locality, most notably Bruce Wade, who published on the entire known fauna; Norman Sohl, who published on the gastropods; Cobban and Kennedy who published on the ammonites; and Brister and Young, who published an overview on the fauna and history of Coon Creek at the type locality from the extensive collections made by the Pink Palace Museum. Except for Discoscaphites the ammonite fauna from this locality compares both at a species level and stratigraphically with the fauna from the Nacatoch Sand in Kaufman and Navarro Counties of Texas (Stephenson, 1941). Except for Discoscaphites nearly all of the ammonite fauna also correlates to the Baculites cuneatus through Baculites jenseni Zones of the Pierre and Bearpaw Shales in the Western Interior, most notably to that from the Middle Park and Fort Collins area of Colorado as reported by Kennedy et al. (2000). Because the aragonitic shell of this cephalopod fauna is so well preserved at this locality it makes it possible to give a more complete description of some of the heteromorph ammonite species than had been previously done, most importantly the rib indexes. Both invertebrate and vertebrate researchers have published that the fauna from the type locality of the Coon Creek Formation constitutes a lower Maastrichtian fauna. The presence of Cirroceras conradi, Hoploscaphites reesidei, Solenoceras reesidei, S. texanum, and Nostoceras (Nostoceras) hyatti places the age of the Coon Creek Tongue at the type locality at upper Late Campanian (72-71.5 MYA), the equivalent age of the Baculites reesidei through B. jenseni Zones of the Western Interior. This is the first reported occurrence for Pachydiscus arkansanus, Lewyites, Hoploscaphites cf. H. brevis and Discoscaphites from the Coon Creek Formation at its type locality.