Range
The ophiuroids diverged in the Early Ordovician, about 500 million years ago. Ophiuroids can be found today in all of the major marine provinces, from the poles to the tropics. In fact, crinoids, holothurians, and ophiuroids live at depths from 16–35 m, all over the world. Basket stars are usually confined to the deeper parts of this range. Ophiuroids are known even from abyssal (>6000 m) depths. However brittle stars are also common, if cryptic, members of reef communities, where they hide under rocks and even within other living organisms. A few ophiuroid species can even tolerate brackish water, an ability otherwise almost unknown among echinoderms. A brittle star's skeleton is made up of embedded ossicles.
Read more about this topic: Brittle Star
Famous quotes containing the word range:
“The Canadians of those days, at least, possessed a roving spirit of adventure which carried them further, in exposure to hardship and danger, than ever the New England colonist went, and led them, though not to clear and colonize the wilderness, yet to range over it as coureurs de bois, or runners of the woods, or, as Hontan prefers to call them, coureurs de risques, runners of risks; to say nothing of their enterprising priesthood.”
—Henry David Thoreau (1817–1862)
“For generations, a wide range of shooting in Northern Ireland has provided all sections of the population with a pastime which ... has occupied a great deal of leisure time. Unlike many other countries, the outstanding characteristic of the sport has been that it was not confined to any one class.”
—Northern Irish Tourist Board. quoted in New Statesman (London, Aug. 29, 1969)
“Viewed freely, the English language is the accretion and growth of every dialect, race, and range of time, and is both the free and compacted composition of all.”
—Walt Whitman (1819–1892)