SYSTEMATIC REVISION OF CRINOIDS FROM THE ST. LOUIS LIMESTONE (MERAMECIAN, ILLINOIS BASIN)

Very little attention has been paid to crinoids of the St. Louis Limestone since the 19^th century. Now that the stratigraphic boundaries of the formation have been delineated (Maples and Waters, 1987) and a collection of crinoids (Harris Stone Quarry, Bainbridge, Indiana) specific to the St. Louis has become available, updated systematics are possible for the crinoids of that formation. The literature (Bassler and Moodey, 1943; Webster, 2003) lists 28 species from the St. Louis Limestone, including 14 camerates, 3 primitive cladids, 9 advanced cladids and 2 flexibles. After evaluation of the available specimens, and analysis of the literature, 22 species are recognized, including 11 camerates, 1 primitive cladid, 8 advanced cladids and 2 flexibles. Six species were rejected including Amphoracrocrinus amphora, Cyathocrinites globosus, Dichocrinus parvulus, Platycrinites faberi, Platycrinites huntsvillae and Plaxocrinus sanctiludovici. Three species were synonymized including Aphelecrinus peculiaris to A. scoparius, Cyathocrinites macadamsi to Cymbiocrinus dactylus and Poteriocrinites arrectarius to Phacelocrinus vanhornei. One new species of Armenocrinus was identified. Two species, Stinocrinus? sp. and Cribanocrinus coxanus, were added that were not previously identified within the St. Louis. Nineteen species were retained as previously listed. These include Aphelecrinus scoparius, Azygocrinus euconus, Barycrinus spectabilis, Camptocrinus cirrifer, Camptocrinus myelodactylus, Culmicrinus missouriensis, Cymbiocrinus dactylus, Hyrtanecrinus ornatus, Onychocrinus magnus, Pachylocrinus norwoodi, Phacelocrinus dactyliformis, Phacelocrinus vanhornei, Platycrinites niotensis, Platycrinites pumilus, Platycrinites sarae, Talarocrinus cornigerus, Talarocrinus sexlobatus, Talarocrinus simplex and Taxocrinus shumardianus. These 22 crinoid species help document the transition from predominantly many plated, larger calyx camerates of the underlying Meramecian rocks to the more sparsely plated, smaller calyx camerates and advanced cladids of the overlying Chesterian.