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Unusual crinoids from the Ramp Creek Formation (Mississippian), Indian Creek, Montgomery County, Indiana
Published online by Cambridge University Press: 14 July 2015
Abstract
Three new species of inadunate crinoids of Early Mississippian age from the Ramp Creek Formation along Indiana Creek, southern Montgomery County, Indiana, are described. Poteriocrinites amplus n. sp. is the first correctly identified record from North America of this long-ranging Old World genus. Poteriocrinites macropleurus and P. doris from the Burlington Limestone are here reassigned to Springericrinus. Interchange of Mississippian crinoid genera between Europe and North America is rare, many genera being endemic. Springericrinus sacculus n. sp. is the youngest reported species of this North American counterpart of Poteriocrinites. This new species exhibits two advanced features: presence of only one, rather than three, anal plate, and presence of 3 or 4, rather than 1 or 2, primibrachial plates per ray. The third species, Decadocrinus stellatus n. sp., presents an interesting blend of characters usually used as generic discriminators between Decadocrinus and Histocrinus. The specimen could possibly be considered to be an intermediate between these two genera that are currently placed, incorrectly we believe, in two separate superfamilies.
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