Glyptocrinus

Classification
Phylum: Echinodermata
Class:Crinoidea
Order: Monobathrida
Family: Glyptocrinidae
Genus: Glyptocrinus Hall, 1847
Cincinnatian Species: Glyptocrinus decadactylus, Glyptocrinus fornshelli

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Geologic Range
Middle Ordovician – Late Silurian

Common Paleoecology
Glyptocrinus is an extinct genus of stationary upper-level epifaunal suspension feeders

Identification in Hand Sample:

Distinguished by rays that branch twice on the calyx, such that twenty arms exit from the calyx
Arms 20, simple or branching once, uniserial
Basals numbering 5
Primary radials, three by five; secondary radials, one or more by ten

Geographic Occurrences

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Holland (UGA Strat Lab, 2013):

Glyptocrinus is distinguished by rays that branch twice on the calyx, such that twenty arms exit from the calyx. In Pycnocrinus, the rays bifurcate once on the calyx; the ten arms immediately branch above the calyx, forming twenty arms.

Treatise on Invertebrate Paleontology, Part T, Vol. 2(2) (1978):

Secundibrachs 2 in each ray; fixed tertibrachs passing to free arms. Arms 20, simple or branching once, uniserial; brachials cuneate externally.

Miller(1883):

In the light of these preliminary rules, it is proposed that the genus Glyptocrinus shall be confined to those species possessing the following three characters, to-wit : basals, five ; primary radials, three by five; and secondary radials, one or more by ten.

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G. decadactylus

G. fornshelli