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The numerous calcareous plates make up the bulk of the crinoid, with only a small percentage of soft tissue. These ossicles fossilise well and there are beds of limestone dating from the Lower Carboniferous around Clitheroe, England, formed almost exclusively from a diverse fauna of crinoid fossils. [15] Stalked crinoid drawn by Ernst Haeckel
Crinoid fossils from the Jurassic showing ossicles. Several types of small ossicles are found in the body wall of sea cucumbers. Baskets are cup-shaped and usually have four projections. Buttons are disc-shaped and pierced by four holes and may be smooth or knobbed.
In this fossil-rich bed have been found the fossils of sixty species of crinoid, distributed among more than forty genera. It is thought that the various species had different length stalks so that they could capture plankton drifting past at various heights above the substrate. The fossil beds were formed at a time when the seabed was much ...
Articulata are a subclass or superorder within the class Crinoidea, including all living crinoid species. They are commonly known as sea lilies (stalked crinoids) or feather stars (unstalked crinoids). The Articulata are differentiated from the extinct subclasses by their lack of an anal plate in the adult stage and the presence of an ...
Pentacrinites are commonly found in the Pentacrinites Bed of the Early Jurassic (Lower Lias) of Lyme Regis, Dorset, England. [2] 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.
The breakage of the stem during the animal's life was a common occurrence, and it often survived long enough to form a new end on its shortened stem. [3] Being from the Middle Triassic, Encrinus is the last known from its group of crinoids, as most others died out during the Permian–Triassic extinction event. [1]
Flexible fossils are very rare in the Ordovician (the most common taxa being Cupulocrinus and Protaxocrinus), but the Late Ordovician appears to have been an interval of rapid diversification for the group. [3] Major traits of Flexibilia include: [1] [4] Three infrabasal plates (in contrast to the five found in other dicyclic crinoids).
This genus is known in the fossil record from the Devonian period to the Permian period (age range: 360.7 to 290.1 million years ago). [3] Fossils of species within this genus have been found in Australia, China, Europe and United States.