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
REFERENCES
[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).
No comments:
Post a Comment
Markup Key:
- <b>bold</b> = bold
- <i>italic</i> = italic
- <a href="http://www.fieldofscience.com/">FoS</a> = FoS