[2] It can be confused with Crossaster papposus , the only British species with a similar number of arms, but S. endeca has a smoother aboral surface.

[3][4][5] The purple sun star occurs in the northeastern Atlantic Ocean and the North Sea at depths to 450 m (1,480 ft).

Its typical habitats are muddy sand, gravel, or rocky areas with deposited sediment.

In the Atlantic Ocean, it feeds on other starfish and bivalve molluscs, but in the Pacific, its diet is mainly sea cucumbers and other invertebrates.

[5] After six weeks, the sucker is resorbed and the juvenile starfish begins to move about with its tube feet.