The longnose sawtail catshark (''Galeus longirostris'') is a little-known

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

catshark Catsharks are ground sharks of the family Scyliorhinidae. They are the largest family of sharks with around 160 species placed in 17 genera. Although they are generally known as catsharks, some species can also be called dogfish due to previous n ...

, part of the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Scyliorhinidae, found off the northwestern

Pacific The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...

islands of

Amami Ōshima , also known as Amami, is the largest island in the Amami archipelago between Kyūshū and Okinawa. It is one of the Satsunan Islands. The island, 712.35 km2 in area, has a population of approximately 73,000 people. Administratively it is d ...

, Ogasawara, and

Izu Izu may refer to: Places *Izu Province, a part of modern-day Shizuoka prefecture in Japan **Izu, Shizuoka, a city in Shizuoka prefecture **Izu Peninsula, near Tokyo **Izu Islands, located off the Izu Peninsula People with the surname

*, Japane ...

at depths of . Reaching a length of , it is characterized by a long flattened snout, a long space between the pelvic and anal fins, and a crest of enlarged

dermal denticle A fish scale is a small rigid plate that grows out of the skin of a fish. The skin of most jawed fishes is covered with these protective scales, which can also provide effective camouflage through the use of reflection and colouration, as we ...

s along the dorsal

caudal fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as se ...

edge. Adults are plain dark gray above, while juveniles have a few faint dark saddles on the back and tail.

Taxonomy

The first known specimen of the longnose sawtail catshark was hooked on a bottom

longline Long line or longline may refer to: *''Long Line'', an album by Peter Wolf *Long line (topology), or Alexandroff line, a topological space *Long line (telecommunications), a transmission line in a long-distance communications network *Longline fish ...

off the

Ogasawara Islands The Bonin Islands, also known as the , are an archipelago of over 30 subtropical and tropical islands, some directly south of Tokyo, Japan and northwest of Guam. The name "Bonin Islands" comes from the Japanese word ''bunin'' (an archaic readi ...

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 In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bot ...

''longirostris'' from the

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

''longus'' ("long"), and ''rostrum'' ("snout"). A long female caught off

was designated as the

type specimen In biology, a type is a particular wiktionary:en:specimen, specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally attached. In other words, a type is an example that serves to a ...

. Within the genus, this species most closely resembles the

broadfin sawtail catshark The broadfin sawtail catshark (''Galeus nipponensis'') is a common species of catshark, part of the family Scyliorhinidae. It is found on or near the bottom at depths of , from southeastern Japan to the East China Sea. A slender species growing ...

(''G. nipponensis'').

Distribution and habitat

The longnose sawtail catshark has been recorded from south of

Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...

, off the islands of Amami Ōshima, Ogasawara, and

*, Japane ...

. This

demersal The demersal zone is the part of the sea or ocean (or deep lake) consisting of the part of the water column near to (and significantly affected by) the seabed and the benthos. The demersal zone is just above the benthic zone and forms a layer of ...

species inhabits upper insular slopes at a depth of , and is reportedly rather common.

Description

One of the larger members of the genus, the longnose sawtail catshark grows to at least 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 The nictitating membrane (from Latin '' nictare'', to blink) is a transparent or translucent third eyelid present in some animals that can be drawn across the eye from the medial canthus to protect and moisten it while maintaining vision. All ...

s (protective third eyelids) and have thin ridges underneath. There is a medium-sized

spiracle Spiracle or spiraculum may refer to: * Spiracle (arthropods), opening in the exoskeletons of some arthropods * Spiracle (vertebrates), openings on the surface of some vertebrates * Spiraculum, a genus of land snails in family Cyclophoridae Cycl ...

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 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 and rays, as well as deep-branching vertebrates such as lampreys. In con ...

s are short, with the fifth pair over the

pectoral fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as ...

bases. The origins of the first and second

dorsal fin A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through conv ...

s lie over the latter half of the

pelvic fin Pelvic fins or ventral fins are paired fins located on the ventral surface of fish. The paired pelvic fins are homologous to the hindlimbs of tetrapods. Structure and function Structure In actinopterygians, the pelvic fin consists of two en ...

s and the midpoint of the

anal fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as se ...

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

s are of moderate size; the

claspers In biology, a clasper is a male anatomical structure found in some groups of animals, used in mating. Male cartilaginous fish have claspers formed from the posterior portion of their pelvic fin which serve to channel semen into the female's ...

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 Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as se ...

is compressed from side to side, and leads to a low

with a small lower lobe and a ventral notch near the tip of the upper lobe. The

s 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 Bycatch (or by-catch), in the fishing industry, is a fish or other marine species that is caught unintentionally while fishing for specific species or sizes of wildlife. Bycatch is either the wrong species, the wrong sex, or is undersized or juve ...

in deepwater

trawl Trawling is a method of fishing that involves pulling a fishing net through the water behind one or more boats. The net used for trawling is called a trawl. This principle requires netting bags which are towed through water to catch different speci ...

fisheries Fishery can mean either the enterprise of raising or harvesting fish and other aquatic life; or more commonly, the site where such enterprise takes place ( a.k.a. fishing ground). Commercial fisheries include wild fisheries and fish farms, both ...

. The

International Union for Conservation of Nature The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...

(IUCN) has listed it as

Least Concern A least-concern species is a species that has been categorized by the International Union for Conservation of Nature (IUCN) as evaluated as not being a focus of species conservation because the specific species is still plentiful in the wild. T ...

References

{{Taxonbar, from=Q936319 longnose sawtail catshark Fish of Japan Endemic fauna of Japan longnose sawtail catshark