- Copyright © 2016, The Paleontological Society
The Actinocrinitidae were among the most abundant crinoids worldwide during the Lower Mississippian. Recent systematic revisions of the family allow a revised genus- and species-level understanding of these crinoids globally and a more precise means by which to understand the temporal and facies distribution of genera and species in this important Mississippian family. Two genera with a total of five species of Actinocrinitidae (and five additional forms left in open nomenclature) are recognized from the Fort Payne Formation, including Actinocrinites jugosus (Hall, 1859), Actinocrinites spp. indeterminate, Thinocrinus gibsoni (Miller and Gurley, 1893), Thinocrinus lowei (Hall, 1858), Thinocrinus probolos (Ausich and Kammer, 1991), Thinocrinus akanthos new species, Thinocrinus sp. aff. T. gibsoni, Thinocrinus spp. indeterminate, and two taxa recognized as only Actinocrinitidae genus and species indeterminate. Actinocrinites tripus Ehlers and Kesling, 1963 is recognized as a junior synonym of Thinocrinus gibsoni. Thinocrinus, rather than Actinocrinites as previously thought, is the dominant Fort Payne Formation actinocrinitid. Fort Payne Formation carbonate buildup facies (wackestone buildups and crinoidal packstone buildups) each have characteristic species of Thinocrinus. Actinocrinites is relatively rare in the Fort Payne Formation, but occurs preferentially in crinoidal packstone buildups.