Well-preserved specimens are found in the limestone cliffs along the Mississippi River between Burlington and Alton. The oldest crinoids come from Ordovician rocks. Some crinoids live today, mainly in deep parts of the ocean, but they are not nearly as common as in the past.

What rocks are crinoids found in?

Crinoids are common fossils from Paleozoic-age marine rocks, although none have been found in Cambrian rocks (505—5 70 million years ago). Crinoids were sometimes so diverse and abundant that beds of limestone hundreds of feet thick were formed.

What environment do crinoids live in?

They live in both shallow water and in depths as great as 9,000 meters (30,000 ft). Those crinoids which in their adult form are attached to the sea bottom by a stalk are commonly called sea lilies, while the unstalked forms are called feather stars or comatulids, being members of the largest crinoid order, Comatulida.