Good afternoon! The Word of the Day is:
- Crinoid-
Pronounced cry-noyd
n. any echinoderm (a phylum of marine animals) of the class Crinoidea, having a cup-shaped body to which are attached branched, radiating arms, comprising the sea lilies, feather stars, and various fossil forms
Word Origin
The word "krinoeides," meaning "lily-like," dates from around 1836.
More Information
Crinoids are known to have delicate feathery arms radiating from a central disc. The group includes the free-swimming feather stars, the sessile sea lilies, and many stemmed fossil forms. The arms contain reproductive organs and sensory tube feet. The tentacles also have open grooves, which cilia (minute, hairlike projections) sweep along, moving food particles toward the mouth.
Although the basic echinoderm pattern of five-fold symmetry is the most recognizable, most crinoids have many more than five arms. Crinoids usually have a stem used to attach themselves to a substrate, but many live attached only as juveniles and become free-swimming adults.
Crinoids were common during the Paleozoic Era and are important index fossils. The crinoids underwent two periods of abrupt adaptive radiation; the first was during the Ordovician period, and the other occurred after they underwent a selective mass extinction at the end of the Permian period.
Check out this youtube video of a crinoid! http://www.youtube.com/watch?v=s1xfRc4SDsw
