Glyptocrinus fornshelli

Classification
Phylum: Echinodermata
Class: Crinoidea
Order: Monobathrida
Family: Glyptocrinidae
Genus: Glyptocrinus
Species: Glyptocrinus fornshelli (Miller, 1874)

G.fornshelli_paleoeco

Stratigraphic Occurrences

G. fornshelli_strat

Geographic Occurrences

Map point data provided by iDigBio.

Stratigraphic Description

Sequences (Formations)

  • C5 Sequence (Waynesville)

Identification in Hand Sample

  • Body obconoidal, about 1.5 times as high as wide and tapering to the column
  • First radials much larger than basals, heptagonal, nearly as wide as long
  • Second radials octagonal, as long but not as wide as the first
  • Third radials heptagonal, about the size of the second, each supporting two secondary radials
  • Column pentagonal instead of round

Glyptocrinus fornshelli from Oldenburg, Indiana (CMC 53954)

Published Description

Holland (UGA Strat Lab, 2013):

  • More conical cup than Pycnocrinus dyeri

Aushich (1996):

  • Furthermore, among Ordovician crinoids, lumen angles have a consistent relationship, with one known exception, the Late Ordovician Glyptocrinus fornshelli Miller. Wachsmuth and Springer (1897) first recognized this symmetry anomaly. It either records a true anomaly, or G. fornshelli is a pseudomonocyclic crinoid. The former explanation is preferred at the present time because the CD interray is consistent with those of other Ordovician glyptocrinids.

Bather (1898):

  • Wachsmuth and Springer say there are two, “and, so far as we know, only two. In Pentacrinus [=Isocrinus] and the monocyclic Glyptocrinus Fornshelli, S. A. Miller, the axial canal has the same orientation as the outer angle of the stem.”
  • Wachsmuth and Springer say that the structure of Pentacrinus [=Isocrinus] “simply points to the existence in some groups of transition forms intermediate between Monocyclica and Dicyclica” (p. 66), and again, the structure of G. Fornshelli “proves nothing more than that in this species the monocyclic stage was as yet incompletely developed.”

James (1895) :

  • Body obconoidal, about 1.5 times as high as wide and tapering to the column; basals 5, pentagonal, wider than high; first radials much larger than basals, heptagonal, nearly as wide as long, inserted in angle produced by two basals; second radials octagonal, as long but not as wide as the first; third radials heptagonal, about the size of the second, each supporting two secondary radials; secondary radials 5, first two nearly as large as the primary radials, others much smaller; interradial series consists of 1 hexagonal plate in the first range, 2 in the second, 3 in the third; above these about twenty pieces irregularly disposed in ranges, varying from pentagonal to heptagonal, gradually becoming smaller above.
  • Intersecondary radial areas, each occupied by about twelve pieces, the first heptagonal, the second hexagonal, and above ranges of two, until near the top, where there are three pieces between the secondary radials; each basal marked with converging lines on a side; each triangle on the radials marked by parallel lines at right angles to the side of the plate; these lines continue over on the interradial pieces, but never cross each other, the ends being separated by a row of dots; arms arise from the thirds secondary radial, and become free on leaving the fifth without bifurcating; consists of round, wedge-shaped pieces, each supporting a pinnule; bifurcate on the twelfth piece, and again and again between the twentieth and fortieth pieces; pinnules long, and closely arranged along the inner lateral margins; column sharply pentagonal, composed of alternately thick and thin pieces.
  • A beautifully ornamented species, intermediate between decadactylus and dyeri in the number of secondary radials and having the column pentagonal instead of round.