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Document Type

Research

Keywords

Paleontology, Silurian, Llandoverian, Hopkinton Dolomite; eastern Iowa; Crinoidea, Camerata; new genera Luxocrinus, Allozygocrinus, Pregazacrinus, Bolicrinus, Thomasocrinus, Krinocrinus, Archaeocalyptocrinus, and Theleproktocrinus; new speciesLuxocrinus simplex, Dimerocrinites ( Dimerocrinites) sculptus, D. (D .) hopkintonensis, Allozygocrinus dubuquensis, Pregazacrinus hemisphericus, Carpocrinus bodei, Bolicrinus globosus, B. deflatus, Thomasocrinus cylindrica, Krinocrinus i'lflatus, Macrostylocrinus compressus, M. vermiculatus, Allocrinus ornatus, Marsupiocrinus (Amarsupiocrinus) primaevus, Archaeocalyptocrinus nodosus, A. iowensis, and Theleproktocrinus davidsoni

Abstract

Large and diverse Lower Silurian (late Llandoverian) camerate crinoid faunas from the Hopkinton Dolomite of eastern Iowa form the basis of the present study and partially fill the long gap between previously known Late Ordovician and Middle Silurian (Wenlockian) faunas. Taxa are considered in detail up to and including superfamilial level. Several superfamilies and 12 families are recognized covering 20 genera, of which 8 are new. Three subgenera are recognized, one of which (Eucrinus) was originally described as a discrete genus. Thirty-eight species are recognized, 17 of which are described as new taxa, but 15 are relegated to an informal (unnamed) status due to preservational difficulties. New genera are Luxocrinus, Allozygocrinus, Pregazacrinus, Bolicrinus, Thomasocrinus, Krinocrinus, Archaeocalyptocrinus, and Theleproktocrinus. New species are Luxocrinus simplex, Dimerocrinites(Dimerocrinites) sculptus, D. (D.) hopkintonensis, Allozygocrinus dubuquensis, Pregazacrinus hemisphericus, Carpocrinus bodei, Bolicrinus globosus, B. deflatus, Thomasocrinus cylindrica, Krinocrinus inflatus, Macrostylocrinus compressus, M. vermiculatus, Allocrinus ornatus, Marsupiocrinus (Amarsupiocrinus) primaevus, Archaeocalyptocrinus nodosus, A. iowensus, and Theleproktocrinus davidsoni. Stratigraphy of the Hopkinton Dolomite has been summarized elsewhere and is not extensively discussed. New information on the phylogeny of the Silurian camerate crinoids, as interpreted from the Hopkinton collections, has modified and expanded the understanding of an Early Silurian evolutionary radiation.

Publication Date

September 1981

Journal Title

Proceedings of the Iowa Academy of Science

Volume

88

Issue

3

First Page

101

Last Page

137

Copyright

© Copyright 1981 by the Iowa Academy of Science, Inc.

Language

EN

File Format

application/pdf

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