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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 ...
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.
Anatomy of a stalked crinoid. The basic body form of a crinoid is a stem (not present in adult feather stars) and a crown consisting of a cup-like central body known as the theca, and a set of five rays or arms, usually branched and feathery.
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 ...
Ossicles are small calcareous elements embedded in the dermis of the body wall of echinoderms. They form part of the endoskeleton and provide rigidity and protection. They are found in different forms and arrangements in sea urchins, starfish, brittle stars, sea cucumbers, and crinoids. The ossicles and spines (which are specialised sharp ...
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).
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 .
Fossil crinoid. This list of crinoid genera is an attempt to create a comprehensive listing of all genera that have ever been considered to be crinoids, excluding purely vernacular terms.