The Crinoid Tegmen

Crinoids were and are feeding animals, which necessitates a mouth and anus. Like most echinoderms the crinoids have a one-way digestive tract with a mouth, some sort of gut system, and an anus. Unfortunately for the crinoids their mouth and anus are situated side by side within the tegmen. the anal opening is protected by the anal pyramid, a plate covered dome protruding from the tegmen. The tegmen is located on the dorsal region of the cup, surrounded by the upward reaching feeding arms. The mouth is strategically positioned at the base of the feeding arms which use their ciliated ambulacral grooves to transport the collected food particles down the arms to the mouth. While feeding, the tiny cover plates that protect the tegmen and the many tube feet open up allowing food to enter the mouth.