GILMOCRINUS KENTUCKYENSIS N. SP. FROM THE LATE OSAGEAN (MISSISSIPPIAN) MULDRAUGH MEMBER OF THE BORDEN FORMATION IN KENTUCKY: A EUROPEAN IMMIGRANT ORIGINALLY DERIVED FROM NORTH AMERICA?

Abstract

Crinoids flourished during the Early Mississippian, with late Osagean crinoids being among the most diverse and well studied. Among others, late Osagean crinoid faunas include the well-known Crawfordsville and Indian Creek localities in Montgomery County, Indiana (Van Sant and Lane, 1964; Lane, 1973), and the Keokuk Limestone in the Mississippi River valley stratotype region. The late Osagean faunas in North America have been comprehensively revised recently in a series of studies (Ausich and Kammer, 1990, 1991a, 1991b, 1992; Ausich and Meyer, 1992; Kammer and Ausich, 1992, 1993, 1994, 1996; Ausich et al., 1997, 2000; Meyer and Ausich, 1997). Recently, a new species of the cladid crinoid genus Gilmocrinus Laudon, 1933 was discovered by Goldstein in the Muldraugh Member of the Borden Formation in north-central Kentucky at the same locality studied by Ausich et al. (2000), raising the total species richness at this locality to 67. This single, small specimen is especially significant because of its implications for the geographic distribution of crinoids between North America and Western Europe during the Early Mississippian. In North America, Gilmocrinus was previously known only from the late Kinderhookian Stage (Webster, 2003). Gilmocrinus kentuckyensis n. sp. extends the range of the genus into the late Osagean Stage. There are no reports of Gilmocrinus from the early and middle Osagean of North America, although there are at least 55 species of advanced cladids known from this time interval in the Burlington Limestone (Webster, 2003). In Europe, Gilmocrinus first appears in the early Osagean-equivalent Ivorian Stage and ranges into the late Osagean-equivalent upper Chadian Stage, thus covering the span of time that Gilmocrinus is missing in North America. These biogeographic occurrences suggest that Gilmocrinus originated in North America, migrated to Europe before becoming …