the claspers of mature males are extremely long, reaching past the origin of the anal fin, and have patches of hooks on the underside. The base of the anal fin measures around 11–13% of the total length, about equal to the distance between it and the pelvic fins. The caudal peduncle is compressed from side to side, and leads to a low caudal fin with a small lower lobe and a ventral notch near the tip of the upper lobe. The dermal denticles are small and overlapping, each bearing a median ridge and three marginal teeth. A saw-like crest of enlarged denticles is present along the anterior portion of the dorsal caudal fin edge. Adults are a plain dark gray above and off-white below. The trailing margins of the dorsal and pectoral fins are edged in white, and the pelvic and anal fins are dusky. The inside of the mouth is light gray. Juveniles have faint darker saddles below each dorsal fin, and a few more on the caudal fin. Sharks from Amami Ōshima have faint grayish spots under the pectoral fins. Biology and ecology Virtually nothing is known of the natural history of the longnose sawtail catshark. Males and females mature sexually at around and long respectively. Human interactions While specific data is lacking, the longnose sawtail catshark is likely taken as bycatch in deepwater trawl fisheries. The International Union for Conservation of Nature (IUCN) has listed it as Least Concern. References longnose sawtail catshark Fish of Japan Endemic fauna of Japan longnose sawtail catshark