Xenocrinus baeri

Classification
Phylum: Echinodermata
Class: Crinoidea
Order: Monobathrida
Family: Xenocrinidae
Genus: Xenocrinus
Species: Xenocrinus baeri (Meek, 1872)

Stratigraphic Occurrences

X.baeri_strat

Geographic Occurrences

Map point data provided by iDigBio.

Stratigraphic Description

Sequences (Formations)

  • C5 Sequence (Liberty)

Identification in Hand Sample

  • Radials and fixed brachials dominant plates on calyx and much larger than interradials
  • Free arms not branched; columnals quadrangular
  • Medium sized body and is globose-obconoidal
  • 10 arms, long, simple and widest a little above their bases
  • Column of moderate thickness, rounded to sub-pentagonal near the base and quadrangular along it
Xenocrinus_bayeri_800px

Xenocrinus baeri Unknown formation of unknown locality, near Southwest Ohio (MUGM 28347, left) and from Waynesville formation of Warren County, Ohio (OUIP 1781, right)

Published Description

Holland (UGA Strat Lab, 2013):

  • Calyx with prominent ray ridges; distinctive square stem

Fossils of Ohio (1996) :

  • Radials and fixed brachials dominant plates on calyx and much larger than interradials; radial-plate circlet interrupted by extra plate in posterior; free arms not branched; columnals quadrangular

Meek (1872):

  • Body of about medium size, globose-obconoidal. Subbasal pieces apparently not developed, or very small. Basal pieces short and pentagonal. First primary radials of comparatively moderate size, presenting a general pentagonal outline; second a little narrower than the first, but of nearly the same length, with a general heptagonal outline; third a little narrower than the first, but of nearly the same length, with a general pen­tagonal form. Secondary radials, consisting of about four pieces in succession, on each upper sloping side of each third primary radial; the first two or three of each series only about one-third smn1ler than the second primary radials, while above these the succeeding pieces soon become much shorter free brachials. Inter radial pieces numerous, small, of very unequal size, and without any regularity of arrangement. Anal series unknown, but probably consisting of a mesial series of hexagonal pieces resting one upon another, and a greater number of much smaller pieces irregularly arranged on each side. Axillary spaces each occupied by some six or more very small pieces.
  • Arms ten, rather long, simple, widest a little above their bases, and thence gradually tapering to their ends; composed of very short pieces, so strongly cuneiform as to appear almost to taper to nothing alternately on opposite sides, while each supports a pinnule at its thicker end, along the inner margins. Pinnules very long, moderately short, nearly in contact, and composed of pieces three to four times as long as wide. Surface of body plates without costae or striae; those of the primary and secondary radial series more prominent than the much smaller pieces filling the inter-radial spaces, and thus forming somewhat flattened ridges, more or less interrupted at the sutures, and abruptly beveled at the sides; inter-radial and axillary areas roughened by a minute projecting central point each of the little pieces filling them.Column of moderate thickness, apparently nearly round, or perhaps sub-pentagonal near the base, and composed of alter­nately thicker and thinner pieces, the former of which project a little beyond the others. The body of the only specimens of this species I have seen, are too much distorted by pressure to afford accurate measurements, but it seems to have been about 0•45 inch in height, by a little less in breadth; while its arms measure 0•07 inch in breadth at the widest part, a little above the top of the body, where about eight arm pieces may be counted in a length of the same extent.This species will be readily distinguished from all of the described forms of the genus, resembling it in other respects, by having only ten simple arms, and by the large number and small size of its inter-radial pieces. In the latter character, it resembles G. nealli, of Hall, from which, however, it differs materially in almost every other respect, but more particularly in having only ten instead of twenty arms, which are also stouter. Its inter-radial and axillary spaces likewise differ materially in not being distinctly excavated, and in having each of the little pieces by which they are filled provided with a little projecting point.
  • The specific name is given in honor of Dr. 0. P. Baer, of Richmond, Indiana, to whom I am indebted for the use of the specimens from which the description has been prepared. Locality and position.-Upper part of the Cincinnati group of the Lower Silurian, at Richmond, Indiana.