Pilumnus fissifrons is a small tan to brown crab that is common in rocky areas. Its body and legs are covered in fine, stiff hairs, and it has three large but blunt spines on the carapace behind the eyes. It is virtually indistinguishable from other pilumnid crabs found in SA, except for the presence of several clumps of long, erect and club-shaped hairs (or setae) on the top of the carapace and between the eyes. These features actually make it one of the easier species to identify from this notoriously difficult genus.