A slender species growing to 68 cm (27 in) long, this shark is characterized by a fairly long, pointed snout, a series of indistinct, dark saddles along its back and tail, and a prominent crest of enlarged dermal denticles along the dorsal edge of its caudal fin.

The broadfin sawtail catshark is an opportunistic predator of bony fishes, cephalopods, and crustaceans, with immature and mature sharks being primarily piscivorous.

This shark was formally described as a new species in a 1975 volume of the scientific journal Memoirs of the Faculty of Fisheries, Hokkaido University by Kazuhiro Nakaya, who gave it the specific epithet nipponensis from Nippon (Japan).

The type specimen is a 60 cm (24 in) long adult male caught off Mimase in Kōchi Prefecture, on December 20, 1972.

[3] The broadfin sawtail catshark is found in the northwestern Pacific from Sagami Bay off southeastern Honshu, Japan to the East China Sea, including the Ryukyu Islands and the Kyushu–Palau Ridge.

The snout is rather long, flattened, and pointed, with large nostrils that bear triangular skin flaps on their anterior rims.

The dermal denticles are small and overlapping, each with a leaf-shaped crown bearing a median ridge and three marginal teeth.

The dietary composition of young sharks in Suruga Bay differs from that of the co-occurring gecko catshark (G. eastmani), perhaps to reduce interspecific competition.

It is caught incidentally to an unknown degree in bottom trawls operated by commercial deepwater fisheries off Japan and in the East China Sea.