Arthroacantha carpenteri (Hinde, 1885) - fossil crinoid in shale from the Devonian of Ohio, USA. (public display, Cleveland Museum of Natural History, Cleveland, Ohio, USA)

Crinoids (sea lilies) are sessile, benthic, filter-feeding, stalked echinoderms that are relatively common in the marine fossil record. Crinoids are also a living group, but are uncommon in modern oceans. A crinoid is essentially a starfish-on-a-stick. The stick, or stem, is composed of numerous stacked columnals, like small poker chips. Stems and individual columnals are the most commonly encountered crinoid fossils in the field. Intact, fossilized crinoid heads (crowns, calices, cups) are unusual. Why? Upon death, the crinoid body starts disintegrating very rapidly. The soft tissues holding the skeletal pieces together decay and the skeleton falls apart.

Classification: Animalia, Echinodermata, Crinoidea, Camerata, Monobathrida, Hexacrinitidae

Stratigraphy: Silica Shale (Silica Formation), Middle Devonian