What's a Crinoid Stem?

And limestone, which is a sedimentary rock made up, mostly, of calcium-rich fragments of ancient sea animal skeletons, specifically crinoids. ... Crinoids are often called “sea lilies” because of their resemblance to an underwater flower.

Are crinoid stem extinct?

Crinoids came close to extinction toward the end of the Permian Period, about 252 million years ago. The end of the Permian was marked by the largest extinction event in the history of life. ... Though most crinoids had stems, not all did.

What does the word crinoid mean?

: any of a large class (Crinoidea) of echinoderms usually having a somewhat cup-shaped body with five or more feathery arms — compare feather star, sea lily.