Classification of Echinodermata

	Fossils of extinct blastoids
Picture of an extant sea urchin
	Picture of a small brittle star in sea grass
Red-knobbed starfish from the Indian Ocean
	Picture of a feather star
Picture of a sea cumber in shallow marine water

Kingdom: Animalia

Phylum: Echinodermata

Classes (Extinct):
Arkarua
Helicoplacus
Edioasteroidea
Blastoidea
Somasteroidea

Classes (Extant):
Echinoidea - sea urchins and sand dollars
Holothuroidea - sea cucumbers
Ophiuroidea - brittle stars and basket stars
Asteroidea - sea stars and starfish
Stelleroidea- star fish
Crinoidea - feather stars and sea lilies
Concentricycloidea - sea daisies

The position of Ophiuroidea class in the Echimodermata clade is still uncertain, two hypothesis (see below) have been proposed.

two alternate hypothesis for echimoderm groupings

The Ophiureoidea are the most diverse class if the echinoderms, with more than 250 described genera and 2000 known species. The modern subgroups are outlined below.

Orders of Ophiuroidea
Oegophiurida
Ophiurida - basket stars and serpent stars
Phryophiurida - euryhaline brittle stars

Sub-orders of Oegophiurida
Zeugophiurina

Sub-orders of Ophiurida
Gnathophiurina
Chilophiuruna
Laemorphiurina

Sub-orders of Phryophiurida
Euryalina
Ophimyxia

Ophiuroidea Major Groups

Classification of Echinodermata