Search results
Results from the WOW.Com Content Network
While Echinodermata has been in common use since the mid-1800s, [5] several other names had been proposed. [7] Notably, F. A. Bather called the phylum "Echinoderma" (apparently after Latreille, 1825 [7]) in his 1900 treatise on the phylum, [8] but this name now refers to a fungus.
A brittle star, Ophionereis reticulata A sea cucumber from Malaysia Starfish exhibit a wide range of colours. This List of echinoderm orders concerns the various classes and orders into which taxonomists categorize the roughly 7000 extant species [1] as well as the extinct species of the exclusively marine phylum Echinodermata.
The timeline of the evolutionary history of life represents the current scientific theory outlining the major events during the development of life on planet Earth. Dates in this article are consensus estimates based on scientific evidence , mainly fossils .
Their relatively large sizes, diverse diets and ability to adapt to different environments makes them ecologically important. [64] The term "keystone species" was in fact first used by Robert Paine in 1966 to describe a starfish, Pisaster ochraceus. [65]
Brittle stars are not used as food, [1] though they are not toxic, because of their strong skeleton. Even if some species have blunt spines, no brittlestar is known to be dangerous, nor venomous. There is no harm evidence towards humans, and even with their predators, brittlestars' only means of defense is escaping or discarding an arm.
Echinoderms – 72% of all documented species of Echinodermata are fossils and extinct. [7] Subphylum Crinozoa (sessile echinoderms) – 91% of all documented species of Crinozoa are now extinct Class Crinoidea (crinoids / sea lilies) – See Crinozoa above; Subphylum Blastozoa [†] (extinct blastoids) Class Diploporita; Class Rhombifera
In 1966–7, the Treatise on Invertebrate Paleontology adopted a four-subphylum system to replace Bather's system, in part because of the belief that Eleutherozoa was polyphyletic, although it retained "pelmatozoic" and "eleutherozoic" as descriptions of attached and free-living modes of life, respectively.
Brittle stars do not have a brain or eyes, but they do have a stomach, sex organs, and a mouth with five jaws. They have five long, thin, spiny arms made of calcium carbonate plates [ 2 ] connected by a central disc; the size of their disk ranges from 6-12mm disc diameter (d.d.), and their arms range from sizes greater than 4 times d.d. in length.