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

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

of deepwater catshark, belonging to the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Pentanchidae, 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 the definition, to Antarctica in the south, and is bounded by the cont ...

islands of

Amami Ōshima , also known as Amami, is the largest island in the Amami Islands, Amami archipelago between Kyūshū and Okinawa Prefecture, Okinawa. It is one of the Satsunan Islands, all of which belong to Kagoshima Prefecture, Japan. The island, 712.35 ...

, Ogasawara, and Izu 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 scale (zoology), scales, which can also provide effective Underwater camouflage, camouflage through the us ...

s along the dorsal

caudal fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported only ...

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 off the Ogasawara Islands 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 (biology), taxonomy, binomial nomenclature ("two-term naming system"), also called binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin gramm ...

''longirostris'' from the

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

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

was designated as the

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

. Within the genus, this species most closely resembles the

broadfin sawtail catshark The broadfin sawtail catshark (''Galeus nipponensis'') is a species of shark belonging to the Family (biology), family Pentanchidae, the deepwater catsharks. It is found on or near the bottom at depths of , from southeastern Japan to the East Ch ...

(''G. nipponensis'').

Distribution and habitat

The longnose sawtail catshark has been recorded from south of

Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...

, off the islands of Amami Ōshima, Ogasawara, and Izu. This demersal 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. Most ...

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

s are short, with the fifth pair over the

pectoral fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish aquatic locomotion, swim. Apart from the tail or caudal fin, fish fins have no direct connection with the vertebral column ...

bases. The origins of the first and second

dorsal fin A dorsal fin is a fin on the back of most marine and freshwater vertebrates. Dorsal fins have evolved independently several times through convergent evolution adapting to marine environments, so the fins are not all homologous. They are found ...

s lie over the latter half of the

pelvic fin Pelvic fins or ventral fins are paired fins located on the ventral (belly) surface of fish, and are the lower of the only two sets of paired fins (the other being the laterally positioned pectoral fins). The pelvic fins are homologous to the hi ...

s and the midpoint of the

anal fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported o ...

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 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 moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported only ...

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

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 grounds). Commercial fisheries include wild fisheries and fish farm ...

. The

International Union for Conservation of Nature The International Union for Conservation of Nature (IUCN) is an international organization working in the field of nature conservation and sustainable use of natural resources. Founded in 1948, IUCN has become the global authority on the stat ...

(IUCN) has listed it as

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

References

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