Crinoids are marine organisms that first appeared in the early in the middle of the Cambrian period and that still survive up until the present day. The fossil record shows a world-wide distribution during the geological past. Crinoids were so abundant in the Paleozoic era that their remains form vast thickness' of limestone. These great 'forests' of crinoids probably lived in fairly shallow water. Flower-shaped crinoids have blanketed the seas periodically for more than 440 million years.

They collect food with their 'arms'. Each arm has a double row of tiny appendages, or 'tube feet', lining a mucus tract that runs down to the mouth. Crinoids feed by extending their arms to catch particles that float past. Having caught something, they move it, with their tube feet, up their sticky food grooves and into their mouth. Their menu was limited to organic particles and small organisms suspended in sea water.

The popular names for crinoids are 'sea lilies' (for fixed crinoids) and 'feather stars' (for free-swimming crinoids). Crinoids are members of a group called the Echinoderms which also includes Echinoids (sea urchins) and starfish.

Photographs

A piece of water worn limestone showing both Crinoid stem and fronds.

Pieces of crinoid stem and a crinoid 'ossicle' collected from the Belemnite Marl under Wear Cliffs and Golden Cap.

A piece of Pentacrinite Bed. The iron pyrite is supported by a thin layer of distinctive pinkish calcite. This bed is very fragile and it is unusual to find such a large piece. The crinoid stems can be easily seen.