TAPHONOMY AND PALEOECOLOGY OF THE LATE CARBONIFEROUS-PERMIAN HUGHES CREEK SHALE, RICHARDSON COUNTY, NEBRASKA

Reconstruction of Late Carboniferous-Permian marine paleocommunities is frequently complicated by incomplete preservation of fossil taxa. Taphonomic analysis allows one to assess quality of preservation in order to proceed to subsequent paleoecologic studies. The Late Carboniferous-Permian (~290 million years) Hughes Creek Shale of the Foraker Formation is exposed discontinuously throughout the Forest City Basin of the North American Mid-Continent. While outcrops are extensive in Kansas, surface exposures in Nebraska occur only in the extreme southeastern corner of the state as shales and minor limestone. A measured stratigraphic section (~2m) near the town of Falls City, in Richardson County, Nebraska, contains a diverse and abundant macrofauna dominated by: brachiopods, bryozoans, crinoids, rugose corals and trilobites. Also found within the same area is a shell-crushing shark known as Petalodus ohioensis, discussed is this rare find and a detailed description of the shark and how we think it lived. Taphonomic analysis of the fossils (size-frequency distribution, articulation ratio, pedicle/brachial valve ratio, corrasion, epibiont coverage and fracture type) provides support for a hypothesis of short seafloor residence times for skeletal remains. While biased somewhat by preservation condition, taphonomic analysis strongly suggests that the fauna represents a single paleocommunity, amenable to paleoecologic analysis. Diversity indices (simple species richness, Margalef, Shannon-Weiner, equitability) were calculated by the PAST software program and compared with coeval paleocommunities in the Illinois and West Texas Basins.