The Spongehead catshark is a rare species, the spongehead catshark (Apristurus spongiceps), alive in its natural habitat. Previously, only 2 specimens had been documented.
Also the spongehead catshark is only known from two specimens taken in the Pacific Ocean.
The spongehead catshark has a thick body and head, with a moderately long, broadly rounded snout. The five pairs of gill slits are very small, and the septa between them are covered with unique pleats and folds that extend above and below, over the throat.
The eyes are small and the nostrils are broad, with slit-like incurrent and excurrent openings. The mouth is long, large, and broadly arched, bearing prominently expanded dental bands. The two dorsal fins are about equal in size; the pectoral fins are rather small, while the pelvic fins are high and broadly rounded. The anal fin is short, high, and rounded. The caudal fin is moderately broad. The dermal denticles are closely set and give the skin a fuzzy or felt-like texture. It is dark brown, without fin markings.