Clidochirus springeri, from the Smithsonian National Museum of Natural History.

Belongs within: Inadunata.

The Icthyocrinidae are a group of crinoids known from the early Silurian to the early Carboniferous in which the crown lacks a marked boundary between cup and arms (Moore 1978).

Characters (from Eckert & Brett 2001): Crown ovoid to pyriform without demarcation between cup and arms in lateral view. Infrabasals typically small, visible in side view or concealed. Radianal situated directly below C ray radial. Anal X, if present, occasionally succeeded by additional plates. Anal sac and interbrachials absent. Arms isotomous, proximal brachials sutured laterally.

Icthyocrinidae [Ichthyocrinacea, Ichthyocrinidae, Ichthyocrinites, Icthyocrinacea]
    |–Cleistocrinus Springer 1920 EB01
    |    `–*C. humilis (Angelin 1878) [=Calpiocrinus humilis] M78
    |–Synaptocrinus Springer 1920 EB01
    |    `–*S. nuntius (Hall 1862) [=Forbesiocrinus nuntius] M78
    |–Paraclidochirus Webster & Fox 1986 EB01
    |    |–‘Clidochirus’ gratiosus Strimple 1963 EB01
    |    `–‘Clidochirus’ keyserensis Stringer 1920 EB01
    |–Prolixocrinus Eckert & Brett 2001 EB01
    |    |–*P. nodocaudis Eckert & Brett 2001 EB01
    |    `–P. americanus (Springer 1920) [=Clidochirus americanus] EB01
    |–Metichthyocrinus Springer 1920 EB01
    |    |–*M. burlingtonensis (Hall 1858) [=Ichthyocrinus burlingtonensis] M78
    |    |–M. clarkensis M78
    |    `–M. tiaraeformis (Troost in Hall 1858) [=Ichthyocrinus tiaraeformis, Cyathocrinites tiaraeformis] M78
    |–Ichthyocrinus Conrad 1842 EB01 [=Icthyocrinus M78]
    |    |–*I. laevis Conrad 1842 [=Icthyocrinus laevis] M78
    |    |–I. clintonensis Hall 1852 EB01
    |    `–I. pyriformis M78
    `–Clidochirus Angelin 1878 EB01 [=Clidocrinus (l. c.) M78]
         |–*C. pyrum Angelin 1878 EB01
         |–C. serrulatus Brower 1973 EB01
         `–C. springeri Ausich 1984 EB01

*Type species of generic name indicated


[EB01] Eckert, J. D., & C. E. Brett. 2001. Early Silurian (Llandovery) crinoids from the Lower Clinton Group, western New York State. Bulletins of American Paleontology 360: 1–88.

[M78] Moore, R. C. 1978. Flexibilia. In: Moore, R. C., & C. Teichert (eds) Treatise on Invertebrate Paleontology pt T. Echinodermata 2. Crinoidea vol. 2 pp. T759–T812. The Geological Society of America, Inc.: Boulder (Colorado), and The University of Kansas: Lawrence (Kansas).

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