Sand star

Archaster typicus is a five-limbed star with long, slightly tapering arms with pointed tips. Occasionally three, four, or even six-armed individuals occur. Adults grow to 12 to 15 centimetres (4.7 to 5.9 in) in diameter, with males often being smaller than females. This starfish is adapted to life on the sandy seabed, where it buries in the sediment during high tides and moves over the sediment surface during low tides. The general colour is grey or brownish, variously marked with darker and lighter patches, sometimes forming a chevron pattern. The underside is pale. The body is slightly inflated and there is a whitish madreporite near the centre of the disc. The small armour plates that cover the upper surface of the arms are lined up in neat parallel rows which distinguishes it from the rather similar Astropecten polyacanthus which has similar habits and colouring. The spines, arranged in a marginal fringe, are short, flat and blunter than A. polyacanthus and the tube feet have suckers and not points.