Pentecopterus is a fearsome sight to behold in the seas it prowls. The largest specimens can reach an impressive length of 5 feet 7 inches. Its segmented exoskeleton is dark and imposing, providing both protection and camouflage in the murky waters it calls home. Eight powerful legs, each tipped with sharp claws, propel it through the water with surprising speed and agility. Along its body, Pentecopterus bears a single pair of spines on the third segment of its body, a distinctive feature that sets it apart from its kin. Its chelicerae are short with a serrated edge, perfect for grasping and rending prey.

Pentecopterus inhabits shallow coastal regions and estuaries, lurking in the cloudy disturbed water.