Xenocrinus

Classification
Phylum: Echinodermata
Class: Crinoidea
Order: Monobathrida
Family: Xenocrinidae
Genus: Xenocrinus Miller, 1881
Cincinnatian Species: Xenocrinus baeri

Geologic Range
Late Ordovician

Common Paleoecology
Xenocrinus is an extinct stationary upper-level epifaunal suspension feeder

Identification in Hand Sample:

  • Quadrangular columnals
  • Median ray and anal ridges conspicuous
  • Body, proportionally, rather long and gently expanding, so that its diameter, at the free arms, is only one-half or two-thirds of its length.
  • 10 arms, pinnulae, long and quite in contact

Geographic Occurrences

		

Published Description

Fossils of Ohio (1996):

  • Quadrangular columnals; unusual for echinoderms

Treatise on Invertebrate Paleontology, Part T (1978):

  • (Characteristics of family) Median ray and anal ridges conspicuous; radials usually adjoining each other in all interrays except posterior; sutures between some adjacent radials covered by small supplementary plates; fixed secundibrachs two, if there is further division, otherwise three to four to each half ray; few fixed tertibrachs may be present; interbrachial areas depressed, flexible composed of many small and irregular plates; CD interray with radial-like primanal and median anitaxis of prominent convex plates. Free arms 2, 3 or 4 per ray, unbranched, uniserial or composed of cuneiform and interlocking brachials. Stem quadrangular in cross section, with pentagonal axial canal.

Miller (1881):

  • Body, proportionally, rather long and gently expanding, so that its diameter, at the free arms, is only one-half or two-thirds of its length.
  • Basals, four; no subradials; primary radials three; secondary radials four, five, six or more, which enter into and form part of the cup or body; interradial and inter-secondary radial areas deeply excavated and filled by numerous small plates; azygous interradial area containing a vertical series of plates, to the top of the body, of about the same size as the radial plates, which rest upon the basal plate and occupy the central part of the azygous area, and between which the primary and secondary radials, on either side, there is an excavated area filled by numerous small plates, as in the four regular interradial areas. The vertical series, however, continues to the top of the proboscis, which is prolonged to or beyond the extension of the arms.
  • Arms, ten; pinnulae, long, quite in contact, and some of the lower ones appearing to become incoroporated into the body or cup; column quadrangular.

X. baeri