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:
“In the range of things toddlers have to learn and endlessly review—why you can’t put bottles with certain labels in your mouth, why you have to sit on the potty, why you can’t take whatever you want in the store, why you don’t hit your friends—by the time we got to why you can’t drop your peas, well, I was dropping a few myself.”
—Mary Kay Blakely (20th century)
“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)
“Jane Addams, founder of Hull House, once asked, “How shall we respond to the dreams of youth?” It is a dazzling and elegant question, a question that demands an answer—a range of answers, really, spiraling outward in widening circles.”
—William Ayers, U.S. author. To Teach: The Journey of a Teacher, ch. 7 (1993)