Thromidia brycei, the thick-armed seastar, is a large, obese species of starfish in the family Mithrodiidae.

[1] Thromidia brycei is a large, obese starfish with a relatively small disc and five slightly tapering thick arms.

[1] The skeleton is covered in thick skin which is composed of small plates which are linked by radiating trabeculae.

[2] Thromidia brycei is found in the North Western Australia region.

It is usually found on sandy shallows, mud, or rock typically with red and brown algae or encrusting organisms, often times with sponges, gorgonians, and alcyonacea at depths of 15-150 metres.