海座星是一类已灭绝的棘皮动物，生存于寒武纪早期至石炭纪。无茎（Column），身体扁平，球形或圆柱形，典型的在壳体上具有五条直的或弯曲的由口中伸出来食物沟。

Edrioasteroidea is an extinct class of echinoderms that lived from the Ediacaran (if Arkarua was indeed an edrioasteroid) until the Permian, about 300 million years ago. The living animal would have resembled a pentamerously symmetrical disc or cushion.