| P number: | P549495 |
|---|---|
| Caption: | Pentacrinites briareus, a fossil crinoid. |
| Description: | Fossil crinoids are rarely found complete. After death, they are frequently broken up so that only pieces of stem or brachials, or plates of the calyx are found. However, at times the dead crinoid is quickly buried by sediment, and when this happens they are sometimes preserved entire. The illustrated specimen of Pentacrinites briareus from the lower Jurassic is an example of this. Pentacrinites grows up to one metre in height. Its long stem is formed of a stack of star-shaped plates called columnals. The arms (brachials) branch into a large number of 'pinnules' which, when extended, form a net-like trap for gathering food particles in the sea water and directing it down to the mouth at the top of the calyx. Crinoids are an ancient group of animals that first appeared during the Cambrian times, over 500 million years ago, and can still be found living today. The animal lived in a cup-like structure ('calyx') made of numerous calcite plates. It had many arms ('brachials'), which waved in the sea water above the animal to collect food. The calyx of most crinoids is attached to a long flexible stem, made of a stack of calcite plates ('columnals'), that was anchored to the sea bed, sometimes by a holdfast. |
| Photographer: | Unknown |
| Copyright statement: | NERC |
| Orientation: | Landscape |
| Size: | 468.41 KB; 1000 x 764 pixels; 85 x 65 mm (print at 300 DPI); 265 x 202 mm (screen at 96 DPI); |
| Average Rating: | Not yet rated |
| Categories: | Best of BGS Images/ Fossils |
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