-Different from other invertabrates in that test is secreted from middle body layer rather than outer layer, thus becoming enveloped by soft tissue.
-Each plate or spicule is a single crystal of calcite.
-Consists of a stem surmounted by a calyx of 2 or 3 rows of plates, bearing 5 pinnate arms.
-Arms collect small food particles which are passed into the mouth.
-Palaeozoic crinoidea underwent mass extinction at boundary.
-One genus, the articulate Isocrinus, has been found to have survived which then radiated to form the Mesozoic Crinoidea recovery.
-Very few Triassic age fossils are found, with the recovery essentially post Triassic.
