longer than the others. The five pairs of gill slits are short, with the fourth and fifth pairs over the base of the pectoral fins. The first dorsal fin has a rounded apex and located over the latter third of the pelvic fin bases. The second dorsal fin is similar in shape but much larger than the first, and located over the latter half of the anal fin base. The pectoral fins are moderately large and broad. The medium-sized, rounded pelvic fins are placed fairly close to the pectoral fins. The anal fin is elongated and angular, and separated from the caudal fin by only a deep notch. The narrow caudal fin comprises about one-third of the total length and has a distinct lower lobe and a ventral notch near the tip of the upper lobe. The tiny, well-spaced dermal denticles, each bearing a median ridge and three posterior points, give the skin a velvety texture. A large patch of naked skin extends from the throat and gill region, around the pectoral fins and over the flank and abdomen, to the space between the pelvic and anal fins. Denticles are also absent near the fin margins. This species is dark brown to blackish in color; the naked patches of skin and the interior of the mouth are black. Biology and ecology The longhead catshark is unique among Apristurus species in that the duodenum is not short, but almost as long as the spiral valve intestine. The function of this trait is unknown, as the feeding habits of this shark have not been documented. The longhead catshark is the only known cartilaginous fish that is normally hermaphroditic: some 85% of the population is functionally male or female, but also possesses undeveloped reproductive organs of the opposite sex (called "rudimentary hermaphroditism"). The factors underlying the evolution of this system have yet to be investigated. This species is oviparous; a single partial egg case has been found, which had tendrils on the posterior corners. Males and females attain sexual maturity at lengths of around and long respectively. Human interactions The longhead catshark has no known economic value and as such is not a target of fisheries, though it may be taken as bycatch throughout its range. Even if deepwater fisheries expand, however, the shark would likely to able to elude capture by seeking refuge at greater depths, which is why it has been