Longnose sawtail cat shark
Encyclopedia
The longnose sawtail catshark (Galeus longirostris) is a little-known species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 of catshark
Catshark
Catsharks are ground sharks of the family Scyliorhinidae, with over 150 known species. While they are generally known as catsharks, many species are commonly called dogfish....

, family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

 Scyliorhinidae, found off the northwestern Pacific islands of Amami Oshima
Amami Oshima
is a semi-tropical island in the Amami Islands, which is part of the larger Nansei Islands in Japan. Ōshima literally means big island, and it is the largest of the Amami Islands. It lies roughly halfway between the islands of Okinawa and Kyūshū. Briefly part of the Ryūkyū Kingdom, in 1624 it was...

, Ogasawara, and Izu
Izu Islands
The are a group of volcanic islands stretching south and east from the Izu Peninsula of Honshū, Japan. Administratively, they form two towns and six villages; all part of Tokyo. The largest is Izu Ōshima, usually called simply Ōshima....

 at depths of 350–550 m (1,148.3–1,804.5 ft). Reaching a length of 80 cm (31.5 in), it is characterized by a long flattened snout, a long space between the pelvic and anal fins, and a crest of enlarged dermal denticles along the dorsal caudal fin edge. Adults are plain dark gray above, while juveniles have a few faint dark saddles on the back and tail. The International Union for Conservation of Nature (IUCN) presently lacks the information to assess the conservation status of this species.

Taxonomy

The first known specimen of the longnose sawtail catshark was hooked on a bottom longline off the Ogasawara Islands
Ogasawara Islands
The Bonin Islands, known in Japan as the are an archipelago of over 30 subtropical and tropical islands, some directly south of Tokyo, Japan. Administratively, they are part of Ogasawara Municipality of Ogasawara Subprefecture, Tokyo...

 in 1983. The new species was described by Hiroyuki Tachikawa and Toru Taniuchi in a 1987 issue of the Japanese Journal of Ichthyology, and given the specific epithet longirostris from the Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

 longus ("long"), and rostrum ("snout"). A 68 cm (26.8 in) long female caught off Amami Oshima
Amami Oshima
is a semi-tropical island in the Amami Islands, which is part of the larger Nansei Islands in Japan. Ōshima literally means big island, and it is the largest of the Amami Islands. It lies roughly halfway between the islands of Okinawa and Kyūshū. Briefly part of the Ryūkyū Kingdom, in 1624 it was...

 was designated as the type specimen. Within the genus, this species most closely resembles the broadfin sawtail catshark
Broadfin sawtail catshark
The broadfin sawtail catshark is a common species of catshark, family Scyliorhinidae. It is found on or near the bottom at depths of , from southeastern Japan to the East China Sea...

 (G. nipponensis).

Distribution and habitat

The longnose sawtail catshark has been recorded from south of Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

, off the islands of Amami Oshima, Ogasawara, and Izu
Izu Islands
The are a group of volcanic islands stretching south and east from the Izu Peninsula of Honshū, Japan. Administratively, they form two towns and six villages; all part of Tokyo. The largest is Izu Ōshima, usually called simply Ōshima....

. This demersal species inhabits upper insular slopes at a depth of 350–550 m (1,148.3–1,804.5 ft), and is reportedly rather common.

Description

One of the larger members of the genus, the longnose sawtail catshark grows to at least 80 cm (31.5 in) long. This species has a rather stout body and a flattened head. The snout is notably long, with a rounded tip. The nostrils are large and divided by triangular skin flaps on their anterior rims. The large, horizontally oval eyes are equipped with rudimentary nictitating membrane
Nictitating membrane
The nictitating membrane is a transparent or translucent third eyelid present in some animals that can be drawn across the eye for protection and to moisten it while maintaining visibility. Some reptiles, birds, and sharks have a full nictitating membrane; in many mammals, there is a small...

s (protective third eyelids) and have thin ridges underneath. There is a medium-sized spiracle
Spiracle
Spiracles are openings on the surface of some animals that usually lead to respiratory systems.-Vertebrates:The spiracle is a small hole behind each eye that opens to the mouth in some fishes. In the primitive jawless fish the first gill opening immediately behind the mouth is essentially similar...

 behind each eye. The mouth forms a wide arch and bears well-developed furrows around the corners. The tooth rows number 60–70 in either jaw; each tooth is small, with a narrow central cusp and 3–6 smaller lateral cusplets. The five pairs of gill slit
Gill slit
Gill slits are individual openings to gills, i.e., multiple gill arches, which lack a single outer cover. Such gills are characteristic of Cartilaginous fish such as sharks, rays, sawfish, and guitarfish. Most of these have five pairs, but a few species have 6 or 7 pairs...

s are short, with the fifth pair over the pectoral fin bases.

The origins of the first and second dorsal fin
Dorsal fin
A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...

s lie over the latter half of the pelvic fins and the midpoint of the anal fin respectively. The dorsal fins are roughly triangular with blunt apexes, with the first slightly larger than the second. The large, wide pectoral fins have rounded corners. The pelvic fins are of moderate size; 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 Oshima 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
Sexual maturity
Sexual maturity is the age or stage when an organism can reproduce. It is sometimes considered synonymous with adulthood, though the two are distinct...

 at around 66–71 cm (26–28 in) and 68–78 cm (26.8–30.7 in) long respectively.

Human interactions

While specific data is lacking, the longnose sawtail catshark is likely taken as bycatch
Bycatch
The term “bycatch” is usually used for fish caught unintentionally in a fishery while intending to catch other fish. It may however also indicate untargeted catch in other forms of animal harvesting or collecting...

 in deepwater trawl fisheries. The International Union for Conservation of Nature (IUCN) has listed it under Data Deficient
Data Deficient
Data Deficient is a category applied by the IUCN, other agencies, and individuals to a species when the available information is not sufficient for a proper assessment of conservation status to be made...

.
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