Cystoids

Cystoids Temporal range: Middle Ordovician–Permian PreЄ Є O S D C P T J K Pg N
"Cystoidea" from Ernst Haeckel's Kunstformen der Natur, 1904
Scientific classification
Kingdom:	Animalia
Subkingdom:	Eumetazoa
Phylum:	Echinodermata
Subphylum:	Blastozoa
Class:	Cystoidea

The Middle Ordovician cystoid Echinosphaerites aurantium (Estonia). The test is encrusted by a graptolite (black branches).

The Cystoidea or cystoids, are extinct echinoderms that lived attached to the sea floor by stalks, and are distinguished from other echinoderms by triangular pore openings.

Superficially, the 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.

References

Barnes, Robert D. (1982). Invertebrate Zoology. Philadelphia, PA: Holt-Saunders International. pp. 1008–1009. ISBN 0-03-056747-5. 

This echinoderm-related article is a stub. You can help Wikipedia by expanding it.v · Categories: Echinoderms Echinoderm stubs Wikimedia Foundation. 2010. Игры ⚽ Поможем решить контрольную работу Cystohepatic triangle Cystolepiota Look at other dictionaries: Geologic time scale — This clock representation shows some of the major units of geological time and definitive events of Earth history. The Hadean eon represents the time before fossil record of life on Earth; its upper boundary is now regarded as 4.0 Ga.[1] Other… …   Wikipedia Ordovician — Period 488.3–443.7 million years ago …   Wikipedia Crinoid — Crinoids Temporal range: Ordovician Recent …   Wikipedia Devonian Period — Interval of geologic time from 417 to 354 million years ago; it was the fourth period of the Paleozoic Era. During the Devonian, a giant continent was situated in the Southern Hemisphere (see Gondwana), and other landmasses were located in the… …   Universalium Ordovician Period — Interval of geologic time, 490–443 million years ago, the second oldest period of the Paleozoic Era. It follows the Cambrian and precedes the Silurian. During the Ordovician, many of the landmasses were aligned in the tropics. Life was dominated… …   Universalium Echinosphaerites — ▪ fossil genus  genus of cystoids, an extinct group related to the sea lily and starfish, found as fossils in Ordovician marine rocks (between 505 and 438 million years old). It is a useful guide, or index, fossil for Ordovician rocks and time. * …   Universalium pelma — /pelˈmə/ noun The sole of the foot ORIGIN: Gr pelma, atos sole, stalk • • • pelmatic / matˈik/ adjective Pelmatozōˈa plural noun A division of the Echinodermata, typically stalked, including crinoids and the fossil blastoids and cystoids …   Useful english dictionary 18+ © Academic, 2000-2024 Contact us: Technical Support, Advertising Dictionaries export, created on PHP, Joomla, Drupal, WordPress, MODx. Mark and share Search through all dictionaries Translate… Search Internet Share the article and excerpts Direct link … Do a right-click on the link above and select “Copy Link”