Middle Ordovician – Late Silurian
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
- 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.
- 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.