Cystoids are distinguished from other echinoderms by triangular pore openings.
Superficially, cystoids resembled crinoids, but they had an ovoid, rather than cup-shaped, body. The mouth was at the upper pole of the body, with the opposite end attached to the substratum, often by a stalk, although some stalkless species did exist. The anus lay on the side of the body.
Five, or less commonly three, ambulacral areas ran along the outside of the body, radiating outwards from the mouth. A number of small tentacles either surrounded the mouth, or projected outwards in a row from the ambulacral areas, depending on species.
The most distinctive feature of cystoids was the presence of a number of pores in the rigid skeleton encasing the body. These were most likely respiratory in nature, allowing fluid to flow in or out of the body. In some species, the pores were clustered in distinct regions, but in others they were distributed quite widely over the body surface. See also List of echinodermata orders.
cystoidea, class, extinct, crinozoan, echinoderms, termed, cystoids, that, lived, attached, floor, stalks, they, existed, during, paleozoic, middle, ordovician, silurian, periods, until, their, extinction, devonian, period, temporal, range, middle, ordovician,. Cystoidea is a class of extinct crinozoan echinoderms termed cystoids that lived attached to the sea floor by stalks They existed during the Paleozoic Era in the Middle Ordovician and Silurian Periods until their extinction in the Devonian Period CystoideaTemporal range Middle Ordovician Devonian PreꞒ Ꞓ O S D C P T J K Pg N Cystoidea from Ernst Haeckel s Kunstformen der Natur 1904Scientific classificationKingdom AnimaliaPhylum EchinodermataSubphylum CrinozoaClass Cystoideavon Buch 1846Description editCystoids are distinguished from other echinoderms by triangular pore openings Superficially cystoids resembled crinoids but they had an ovoid rather than cup shaped body The mouth was at the upper pole of the body with the opposite end attached to the substratum often by a stalk although some stalkless species did exist The anus lay on the side of the body Five or less commonly three ambulacral areas ran along the outside of the body radiating outwards from the mouth A number of small tentacles either surrounded the mouth or projected outwards in a row from the ambulacral areas depending on species The most distinctive feature of cystoids was the presence of a number of pores in the rigid skeleton encasing the body These were most likely respiratory in nature allowing fluid to flow in or out of the body In some species the pores were clustered in distinct regions but in others they were distributed quite widely over the body surface See also List of echinodermata orders nbsp A Middle Ordovician cystoid Echinosphaerites aurantium Estonia It is encrusted by a graptolite black branches nbsp Image by Encyclopedia BritannicaSee also editPrehistoric echinoderms Paleozoic echinodermsReferences editBarnes Robert D 1982 Invertebrate Zoology Philadelphia PA Holt Saunders International pp 1008 1009 ISBN 0 03 056747 5 Clarkson E N K 1998 Invertebrate Paleontology and Evolution Oxford UK Blackwell Science p 262 ISBN 0 632 05238 4 nbsp This prehistoric echinoderm related article is a stub You can help Wikipedia by expanding it vte Retrieved from https en wikipedia org w index php title Cystoidea amp oldid 1104858710, wikipedia, wiki, book, books, library,
