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The first record of floor plates in pinnules and the earliest record of an anitaxis in rhodocrinitid diplobathrid camerate crinoids

Published online by Cambridge University Press:  22 February 2021

Thomas E. Guensburg Open the ORCID record for Thomas E. Guensburg [Opens in a new window]
Thomas E. Guensburg*
Affiliation:
IRC, Field Museum, 1400 South Lake Shore Drive, Chicago, IL60605
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Abstract

Restudy of Proexenocrinus inyoensis Strimple and McGinnis, 1972, shows that this earliest-known rhodocrinitid diplobathrid camerate crinoid (late Floian, Early Ordovician) expresses the only known record of ambulacral floor plates within pinnules. These pinnule floor plates are remarkably conserved plesiomorphic expressions, with anatomy similar to floor plates of some of the earliest pentaradiate echinoderms, although on a smaller scale. Proexenocrinus floor plates provide direct skeletal evidence that the general resemblance of blastozoan (eocrinoid, diploporan, rhombiferan) brachioles and crinoid pinnules is the product of homoplasy. Proexenocrinus posterior cup morphology is interpreted to include an anitaxis, a distinctive posterior interray morphology.

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Articles
Information
Journal of Paleontology , Volume 95 , Issue 4 , July 2021 , pp. 800 - 804
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Copyright
Copyright © The Author(s), 2021. Published by Cambridge University Press on behalf of the The Paleontological Society

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