Labidiaster annulatus has a wide central disc and 40 to 45 long narrow rays and can reach a diameter of 60 centimetres (24 in).

These are covered by a membrane with numerous raised projections called papulae, some small spines and a few large triangular pedicellariae, wrench-like organs that can grasp objects.

The rays are crowded together where they join the disc and their aboral surface is similarly clad in overlapping scales in a quadrangular mesh pattern.

Other dietary items were varied and included smaller starfish of this species and brittle stars such as Ophionotus victoriae.

[4] Little is known of the reproduction of Labidiaster annulatus, but the larvae pass through at least one bipinnaria and one brachiolaria stage as has been demonstrated by DNA analysis.

The larvae are planktonic and spend many months drifting with the currents before settling on the seabed and undergoing metamorphosis into juveniles.