Ectenocrinus simplex
GRI #592
This sea lily was found in Ordovician rocks in Ohio. Its slender arms formed a more open fan for collecting particles from the water, and it probably lived in deeper water where currents were slower (Meyer et al., 2002). The arms are branched once above the cup, and bear pinnule-like ramules that are not always easy to see because many specimens are fossilized with their arms tightly clustered. The classification of this disparid crinoid has not yet been fully resolved (Ausich, 2018).
References:
Ausich, W.I., 2018. Morphological paradox of disparid crinoids (Echinodermata): phylogenetic analysis of a Paleozoic clade. Swiss Journal of Palaeontology, 137(2), pp. 159-176. doi:10.1007/s13358-018-0147-z.
Meyer, D.L., Miller, A.I., Holland, S.M. and Dattilo, B.F., 2002. Crinoid distribution and feeding morphology through a depositional sequence: Kope and Fairview Formations, Upper Ordovician, Cincinnati Arch region. Journal of Paleontology, 76(4), pp. 725-732. doi:10.1666/0022-3360(2002)076<0725:CDAFMT>2.0.CO;2.