These animals resemble flowers consisting of a body (calyx) with branched arms, atop a stalk of calcite disks called columnals that is attached to the sea floor by root-like holdfasts stabilizing the substrate.

Petalocrinus and Spirocrinus are crinoids from the Middle Silurian in China. They are extremely distinctive, in that their arms were modified into relatively large, wedge-shaped plates that gave them a flower-like appearance (Petalocrinus), or twisted into spiral forms (Spirocrinus).

Cystoidea are an extinct group of echinoderms that originated in the Ordovician. They resembled crinoids but they lacked true long arms.