Dwarf sawtail catshark
Encyclopedia
The dwarf sawtail catshark (Galeus schultzi) is a little-known species
of catshark
, family
Scyliorhinidae, found exclusively in deep water off Luzon
in the Philippines
. 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
and two dark bands on the caudal fin, as well as a prominent crest of enlarged dermal denticles along the upper caudal fin margin. The International Union for Conservation of Nature (IUCN) does not currently have sufficient information to assess the conservation status of this species.
described the dwarf sawtail catshark in a 1979 National Oceanic and Atmospheric Administration
(NOAA) Technical Report. The type specimen is an adult male 30 cm (11.8 in) long, collected from Balayan Bay
. It does not closely resemble more typical Galeus species, and its placement within the genus is not concrete.
in the Philippines
. It is found on or near the bottom over the upper continental slope at a depth of 329–431 m (1,079.4–1,414 ft), barring a single record from a depth of 50 m (164 ft) on the outer continental shelf
.
s (protective third eyelids). There are low ridges beneath the eyes, and tiny spiracle
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
s.
The two dorsal fin
s have rounded apexes and are similar in size; the first originates over the aft portion of the pelvic fins, and the second over the aft portion of the anal fin. The pectoral fins 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 is nearly cylindrical and leads to a low caudal fin with an indistinct lower lobe and a ventral notch near the tip of the upper lobe. The small, overlapping dermal denticles 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.
at around 25 cm (9.8 in) long, and females at 27 – long.
. The depth range it occupies is not known to be utilized by commercial
trawl fisheries.
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 exclusively in deep water off Luzon
Luzon
Luzon is the largest island in the Philippines. It is located in the northernmost region of the archipelago, and is also the name for one of the three primary island groups in the country centered on the Island of Luzon...
in the Philippines
Philippines
The Philippines , officially known as the Republic of the Philippines , is a country in Southeast Asia in the western Pacific Ocean. To its north across the Luzon Strait lies Taiwan. West across the South China Sea sits Vietnam...
. 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
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...
and two dark bands on the caudal fin, as well as a prominent crest of enlarged dermal denticles along the upper caudal fin margin. The International Union for Conservation of Nature (IUCN) does not currently have sufficient information to assess the conservation status of this species.
Taxonomy
Renowned shark expert Stewart SpringerStewart Springer
Stewart Springer, was a world renowned expert on shark behavior, classification , and distribution of shark populations. There are more than 35 species of sharks, skates, rays, and other animals either classified originally by him or named after him.-Education:Springer was a field naturalist,...
described the dwarf sawtail catshark in a 1979 National Oceanic and Atmospheric Administration
National Oceanic and Atmospheric Administration
The National Oceanic and Atmospheric Administration , pronounced , like "noah", is a scientific agency within the United States Department of Commerce focused on the conditions of the oceans and the atmosphere...
(NOAA) Technical Report. The type specimen is an adult male 30 cm (11.8 in) long, collected from Balayan Bay
Balayan, Batangas
Balayan is a 1st class municipality in the Province of Batangas, Philippines. According to the latest census, it has a population of 79,407 people in 13,843 households....
. 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 to LuzonLuzon
Luzon is the largest island in the Philippines. It is located in the northernmost region of the archipelago, and is also the name for one of the three primary island groups in the country centered on the Island of Luzon...
in the Philippines
Philippines
The Philippines , officially known as the Republic of the Philippines , is a country in Southeast Asia in the western Pacific Ocean. To its north across the Luzon Strait lies Taiwan. West across the South China Sea sits Vietnam...
. It is found on or near the bottom over the upper continental slope at a depth of 329–431 m (1,079.4–1,414 ft), barring a single record from a depth of 50 m (164 ft) on the outer continental shelf
Continental shelf
The continental shelf is the extended perimeter of each continent and associated coastal plain. Much of the shelf was exposed during glacial periods, but is now submerged under relatively shallow seas and gulfs, and was similarly submerged during other interglacial periods. The continental margin,...
.
Description
Reaching a length of 30 cm (11.8 in), 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 membraneNictitating 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). There are low ridges beneath the eyes, and tiny 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...
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 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.
The two 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 have rounded apexes and are similar in size; the first originates over the aft portion of the pelvic fins, and the second over the aft portion of the anal fin. The pectoral fins 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 is nearly cylindrical and leads to a low caudal fin with an indistinct lower lobe and a ventral notch near the tip of the upper lobe. The small, overlapping dermal denticles 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 maturitySexual 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 25 cm (9.8 in) long, and females at 27 – long.
Human interactions
Only a few specimens of the dwarf sawtail catshark have been collected, and a lack of data has led the International Union for Conservation of Nature (IUCN) to list this species as Data DeficientData 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...
. The depth range it occupies is not known to be utilized by commercial
Commercial fishing
Commercial fishing is the activity of catching fish and other seafood for commercial profit, mostly from wild fisheries. It provides a large quantity of food to many countries around the world, but those who practice it as an industry must often pursue fish far into the ocean under adverse conditions...
trawl fisheries.