Crinoidea

Classification
Phylum: Echinodermata
Class: Crinoidea (Miller, 1821)
Cincinnatian Orders: Cladida, Diplobathrida, Disparida, Lichenocrinus, Monobathrida

Geologic Range
Middle Cambrian; Late Ordovician – Holocene

Common Paleoecology
Crinoidea is an extant class of stationary upper-level epifaunal suspension feeders

Characteristics of the Class

• Well developed pentameral symmetry
• Radial growth pattern concentrated on arms and directed away from the theca
• Theca distinctly divided into aboral cup and adoral tegmen
• Well developed column

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Treatise on Invertebrate Paleontology, Part T (1978):

• Crinozoa provided with true arms; pentameral symmetry well developed; theca divided into aboral cup and adoral tegmen, comprising five radial plates from which invariably the aboral skeleton of the arms starts; radial growth pattern concentrated on arms, which are directed away from theca; column ordinarily well developed, lost in postlarval stage in some forms.

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