The dwarf sawtail catshark (''Galeus schultzi'') is a little-known

species In biology, a species is the basic unit of Taxonomy (biology), 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 ...

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 ...

, belonging to the

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

Scyliorhinidae, found exclusively in the deep waters off

Luzon Luzon (; ) is the largest and most populous island in the Philippines. Located in the northern portion of the Philippines archipelago, it is the economic and political center of the nation, being home to the country's capital city, Manila, ...

in the

Philippines The Philippines (; fil, Pilipinas, links=no), officially the Republic of the Philippines ( fil, Republika ng Pilipinas, links=no), * bik, Republika kan Filipinas * ceb, Republika sa Pilipinas * cbk, República de Filipinas * hil, Republ ...

. Unlike other members of its genus, this slender, diminutive shark has a short, rounded snout and very short furrows at the corners of its jaws. It has indistinct darker saddles beneath each

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 c ...

and two dark bands on the

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 s ...

, as well as a prominent 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 w ...

s along the upper caudal fin margin.

Taxonomy

Renowned shark expert

Stewart Springer Stewart Springer (5 June 190623 August 1991) was an American ichthyologist and herpetologist. He was a world-renowned expert on shark behavior, classification ( taxonomy), and population distribution. More than 35 species of sharks, skates, ...

described the dwarf sawtail catshark in a 1979

National Oceanic and Atmospheric Administration The National Oceanic and Atmospheric Administration (abbreviated as NOAA ) is an United States scientific and regulatory agency within the United States Department of Commerce that forecasts weather, monitors oceanic and atmospheric conditi ...

(NOAA) Technical Report. The

type specimen In biology, a type is a particular 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 anchor or centralizes the ...

is an adult male long, collected from

Balayan Bay Balayan Bay is a large bay of Luzon Island in the Philippines. It is part of the Verde Island Passage and its entire shore is in the province of Batangas. The bay is between wide. It is separated from the South China Sea to the west by the Calat ...

.Springer, S. (April 1979). ''A revision of the catsharks, family Scyliorhinidae''. NOAA Technical Report NMFS Circular No. 422: 1–15 It does not closely resemble more typical ''Galeus'' species, and its placement within the genus is not concrete.

Distribution and habitat

The dwarf sawtail catshark is

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found els ...

in the

. It is found on or near the bottom over the upper

continental slope A continental margin is the outer edge of continental crust abutting oceanic crust under coastal waters. It is one of the three major zones of the ocean floor, the other two being deep-ocean basins and mid-ocean ridges. The continental marg ...

at a depth of , barring a single record from a depth of on the outer continental shelf.

Description

Reaching a length of , the dwarf sawtail catshark has a slim, firm body and a distinctively short, rounded snout. The nostrils are divided by triangular flaps of skin on their anterior rims. The horizontally oval eyes are placed somewhat high on the head, and 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 An ...

s (protective third eyelids). There are low ridges beneath the eyes, and tiny

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 ''Spiraculum'' is a genus of operculate land snail ...

s behind them. The large, wide, arched mouth bears very short furrows at the corners. There are 48 tooth rows in the upper jaw, and fewer in the lower jaw; each tooth has a narrow central cusp flanked by lateral cusplets. There are 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 co ...

s. The two

s have rounded apexes and are similar in size; the first originates over the aft portion 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 e ...

s, and the second over the aft portion 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 s ...

. 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 ...

s are large and wide. The pelvic and anal fins are short and low, with angular corners. The base of the anal fin measures 10–11% of the total length, longer than the distances between either the dorsal fins or the pelvic and anal 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 nearly cylindrical and leads to a low

with an indistinct lower lobe and a ventral notch near the tip of the upper lobe. The small, overlapping

s each have a leaf-shaped crown with a median ridge and three teeth on the posterior margin. A crest of enlarged denticles is present along the dorsal caudal fin margin. This species is brownish above and lighter below, with a faint darker saddle beneath each dorsal fin, and two darker bands on the caudal fin. The interior of the mouth varies from light to dusky.

Biology and ecology

The natural history of the dwarf sawtail catshark is poorly known. Males attain

sexual maturity Sexual maturity is the capability of an organism to reproduce. In humans it might be considered synonymous with adulthood, but here puberty is the name for the process of biological sexual maturation, while adulthood is based on cultural definit ...

at around long, and females at long.

Human interactions

Only a few specimens of the dwarf sawtail catshark have been collected. 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 natur ...

(IUCN) to list this species as least concern. The depth range it occupies is not known to be utilized by

commercial Commercial may refer to: * a dose of advertising conveyed through media (such as - for example - radio or television) ** Radio advertisement ** Television advertisement * (adjective for:) commerce, a system of voluntary exchange of products and s ...

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 spe ...

fisheries.

References

{{Taxonbar, from=Q2719468

dwarf sawtail catshark The dwarf sawtail catshark (''Galeus schultzi'') is a little-known species of catshark, belonging to the family (biology), family Catshark, Scyliorhinidae, found exclusively in the deep waters off Luzon in the Philippines. Unlike other members of ...

Fish of the Philippines Endemic fauna of the Philippines Taxa named by Stewart Springer