REAPPRAISAL OF ECHINODERMS FROM THE OIL CREEK FORMATION, MIDDLE ORDOVICIAN (WHITEROCKIAN/DARRIWILIAN), ARBUCKLE MOUNTAINS AND CRINER HILLS, SOUTHERN OKLAHOMA
Published Oil Creek taxa from the dissertation are the crinoid Archaetaxocrinus burfordi (Lewis, 1981) and the rhipidocystid eocrinoid Mandalacystis dockeri (Lewis et al., 1987). Unpublished blastozoans include two specimens of a new asteroblastid diploporan genus; many deltoid plates and two bibrachials of a parablastoid later named Parabolablastus elongatus (Sprinkle & Sumrall, 2008); two partial thecae of a thin-plated, pustular, new paracrinoid?; and distinctive plates of the glyptocystitid rhombiferan Hadrocystis n. sp. Crinoids include a large partial crown of the camerate Reteocrinus n. sp.; three calyces of two new species of the hybocrinid Hybocrinus; a possible new species of the cladid Palaeocrinus; and a possible new species of the cladid Carabocrinus with no? RR-OO slits.
The Oil Creek echinoderm fauna most closely correlates with that in the Kanosh Shale (western Utah) and the Antelope Valley Formation (central Nevada), which share many of the same groups and some of the same genera. Echinoderm diversity in Laurentia slowly increased in the Early and Middle Ordovician before radiating to much higher levels in the better-known Late Ordovician. This diversity pattern is somewhat different than that seen in brachiopods or bryozoans. It is unclear what role preservation and facies may have played in this diversity pattern.