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An Indian bead in Indiana gravel. Indian bead is a colloquial American term for a fossilized stem segment of a columnal crinoid, a marine echinoderm of the class Crinoidea. . The fossils, generally a centimeter or less in diameter, tend to be cylindrical with a small hole (either open or filled) along the axis and can resemble unstrung be
Articulated crinoid fossils are relatively rare, but disarticulated columnals are quite common in the fossil record. They may be extracted from their matrix (often limestone) or, in the case of exposures in coastal cliffs, they can sometimes be found washed out of the matrix and deposited on the foreshore, as if from the sea.
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.
While it has been known that stalked crinoids could move, before this recording the fastest motion known for a stalked crinoid was 0.6 metres (2 feet) per hour. The 2005 recording showed one of these moving across the seabed at the much faster rate of 4 to 5 cm (1.6 to 2.0 in) per second, or 144 to 180 m (472 to 591 ft) per hour. [25]
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.
Crinoids were very abundant in Michigan during the Devonian. [5] Brachiopods are also found in the Devonian, but are less common at that time than they were during the Ordovician. [1] Bryozoans and corals were also present. [5] Plant fossils of this age have been found but are relatively rare.
Agaricocrinus americanus, also known as the mushroom crinoid or American crinoid, is a species of extinct crinoid. Its fossils can be found in the U.S. states of Indiana, Tennessee and Kentucky. They date back to the Lower Mississippian, about 345 million years ago. [1]