Pentacrinites

Pentacrinites is an extinct genus of crinoids that lived from the Hettangian to the Bathonian of Asia, Europe, North America, and New Zealand. Their stems are pentagonal to star-shaped in cross-section and are the most commonly preserved parts. Pentacrinites are commonly found in the Pentacrinites Bed of the Early Jurassic (Lower Lias) of Lyme Regis, Dorset, England. Pentacrinites can be recognized by the extensions (or cirri) all around the stem, which are long, unbranching, and of increasing length further down, the very small cup and 5 long freely branching arms.

== Description == Like most echinoderms, Pentacrinites was composed of numerous calcite plates which were arranged into different body parts. Pentacrinites had 3 kinds of body parts: arms, cup (calyx or theca) and stem. The stem consisted of a stack of numerous 5-sided beads (or columnal plates) with a canal at their centre. The stem had flexible appendages (or cirri) that were used to attach an individual. These cirri themselves were connected to specialized columnals called nodals, leaving oval scars after breaking off. The cirri consisted of diamond-shaped plates with a central canal, less flatted further from the stem. The cup-shaped calyx was very small and consisted of two bands of five plates. These were the bases of the five arms. The top of the calyx was covered by numerous small polygonal plates and the mouth and anus were found on this surface.