| Japanese roughshark | |
|---|---|
| Conservation status | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Chondrichthyes |
| Subclass: | Elasmobranchii |
| Order: | Squaliformes |
| Family: | Oxynotidae |
| Genus: | Oxynotus |
| Species: | O. japonicus |
| Binomial name | |
| Oxynotus japonicus Yano & Murofushi, 1985 |
|
| Range of the Japanese roughshark | |
The Japanese roughshark, Oxynotus japonicus, is a rare species of shark in the family Oxynotidae, known only from a handful of specimens recovered from Suruga Bay and the Enshunada Sea off Japan. It is a benthic species that occurs at a depth of 150–350 meters. This shark is caught (and discarded) as by-catch by bottom trawlers throughout its entire limited range, and may be threatened given the declines in other bottom deep sea species in Suruga Bay.[1]
This species grows to 64.5 cm long.[1] It is similar to other rough sharks in having a stout, high trunk, a dorsally depressed head, and two sail-like dorsal fins with deeply embedded spines. The snout is short, with large nostrils whose lateral and medial apertures are separated by a thick nasal flap. The eyes and spiracles are oval in shape. The five pairs of gill slits are very small and vertical. The mouth is small, with thick, fleshy lips; the teeth in the upper jaw are narrow, erect, and smooth-edged, while those in the lower jaw are broad, blade-like, and smooth-edged. Only one row of teeth in the lower jaw are functional.[2]
The large dorsal fins are subtriangular in shape, with the first dorsal spine sloping slightly backward. The pectoral fins have a convex front margin and a concave rear margin. The anal fin is absent. There is a strong ridge running between the pectoral and pelvic fins on each side of the body. The dermal denticles are large and widely spaced, giving the skin a very rough texture. This species differs from the similar sailfin roughshark in the positioning of the dorsal fins and the shape of the spiracle. The color is a uniform dark brown, with the lips, nasal flap margins, fin axils and inner margins of claspers white.[2]
Reproduction is ovoviviparous, as in other dogfish sharks.[3] Size at maturity is 59 cm long for females and 54 cm long for males.[1]