Late Carboniferous Coiled Nautiloids from the Lost Branch Formation of Oklahoma, Midcontinent North America

Abstract

Abstract. Five species of coiled nautiloids are described from a black concretionary shale (uppermost Desmoinesian; middle upper Carboniferous) of the Lost Branch Formation in northeast Oklahoma, Midcontinent North America. They include a tainoceratid, Metacoceras sp., a grypoceratid, Domatoceras collinsvillense sp. nov., a solenochilid, Solenochilus sp., and the liroceratids, Hemiliroceras reticulatum (Miller and Owen) and Peripetoceras sp. Domatoceras collinsvillense is closely similar to D. umbilicatum Hyatt, but it differs in the possession of a narrower umbilical area and more compressed whorls. New material of H. reticulatum indicates an evolute conch with a shallowly concave impressed zone, characters that warrant the present new combination. The species was previously placed in Coloceras or Liroceras. This discovery of H. reticulatum from the Desmoinesian shale extends downward the stratigraphic range of this genus from the lower Permian to the upper Carboniferous.