SIZE-FREQUENCY DISTRIBUTION AND TAPHONOMY OF BRACHIOPODA FROM THE HUGHES CREEK SHALE (CARBONIFEROUS) OF SOUTHEASTERN NEBRASKA

The Hughes Creek Shale Member of the Foraker Formation (Carboniferous) in Richardson County, Nebraska contains a diverse and abundant open-marine fauna. Species of the Phylum Brachiopoda dominate, although crinoids and bryozoans are also common, while corals, gastropods, trilobites and shark teeth are rare. Two Rhynchonelliform species, the pedunculate Spiriferinid, Hustedia mormoni, and the free-living Strophomenate Dyoros sp., were studied in greater detail as proxy for taphonomy of the entire fauna. Standard length and width measurement was supplemented with articulation ratios as well as qualitative categorizations of corrasion, fragmentation and epibiont coverage for all individuals of the target species. Preliminary results include: skewed size frequency distributions for both with most juveniles absent; high (>95%) articulation for H. mormoni, and moderate (~50%) for D. sp.; low levels of corrasion and epibiont coverage suggesting short seafloor residence times; and low fragmentation, mostly splayed. These results contrast strongly for all taphonomic metrics for the most common brachiopod species of the fauna (e.g. Neospirifer kansasensis, Reticulatia huecoensis)., which also are the largest members of the fauna.