Gaurocrinus nealli

Classification
Phylum: Echinodermata
Class: Crinoidea
Order: Diplobathrida
Family: Reteocrinidae
Genus:Gaurocrinus
Species: Gaurocrinus nealli (Hall, 1872)

Taxonomic Details

Formerly: Reteocrinus nealli

Stratigraphic Occurrences

G. nealli_strat

Geographic Occurrences

Map point data provided by iDigBio.

Stratigraphic Description

Sequences (Formations)

  • C5 Sequence (Liberty, Waynesville)

Identification in Hand Sample

  • Fixed brachials are the dominant plates of the calyx, interradial plates much smaller
  • Characteristic diplobathrid infrabasal plates, and depressed interradial areas
  • Branching free arms numering 20, long.
  • Columnals pentagonal
  • Prominent ray ridges on calyx

G. nealli from the Waynesville Formation of unknown location (CMNH 33150)

Published Description

Holland (UGA Strat Lab, 2013):

  • Prominent ray ridges on calyx; pentagonal stem.

Davis (1998) :

  • Crinoid. delicate crown, showing small calyx, and long, thin arms with pinnules attached. Specimen turned slightly from upright position. Waynesville and Liberty.

Fossils of Ohio (1996):

  • Calyx composed of fixed brachials, interradicals, radials, basals and infrabasals (order Diplobathrida); radials and fixed brachials dominant plates on calyx and much larger than interradial plates; interradial areas depressed; radial-plate circlet interrupted by extra plate in posterior; free arms branched; brachials uniserial; columnals pentagonal.
  • The radials and fixed brachials are the dominant plates of the calyx, and the interradial plates are much smaller. Other distinguishing features of Gaurocrinus nealli include characteristic diplobathrid infrabasal plates, depressed interradial areas, a radial-plate circlet interrupted by an extra plate in the posterior (CD interray), branching free arms and pentagonal columnals.

Broadhead (1987):

  • Internal grooves upon the proximal arm plates of specimens of Gaurocrinus nealli suggest that the nervous system radiating upward from the aboral nerve center continued to follow the proximal, fixed pattern of arm branches extending into the free arms.

Miller (1883):

  • Column sharply pentagonal, and composed of alternating thin and thicker plates. Basals, small, pentagonal, presenting a low triangular face on the exterior, slightly truncated at the lateral angles, and not interfering with the pentalobate character of the calyx when viewed from below. Subradials about as wide as high, except the one on the azygous side, which is longer than wide; each bears a semi-cylindrical three-rayed ridge, highest in the central part, and sending one arm below to meet the angle of the column, and one to each of the adjoining radials to meet corresponding ridges, except as to the azygous subradial, which bears an additional depressed semi-cylindrical ridge extending upward to the superior truncated side. Primary radials,three in each series, except the left posterior ray which has only two. The first and last are pentagonal, and of almost the same size, form and ornamentation, so that by reversing ends they would nearly fill each other’s places. Secondary radials, twelve to about sixteen in each series. The second one gives off a ridge that strengthens the interradial areas. Azygous area covered by more than fifty plates, the middle row being larger and more prominent than the others up to about the sixth plate. Arms, twenty. Pinnules long. It occurs in the upper part of the Hudson River Group.