The Cook's swellshark (''Cephaloscyllium cooki'') 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 ...

, belonging to 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. This shark is found in the

Arafura Sea The Arafura Sea (or Arafuru Sea) lies west of the Pacific Ocean, overlying the continental shelf between Australia and Western New Guinea (also called Papua), which is the Indonesian part of the Island of New Guinea. Geography The Arafura Sea is ...

at a depth of . It is a stocky-bodied shark with a short, broad head and a large mouth, and can be identified by the eight dark, pale-edged saddles along its grayish brown body and tail. The maximum known length of this species is . Like other swellsharks, it can inflate itself with water or air when threatened.

Taxonomy

The Cook's swellshark was described by Peter Last, Bernard Séret, and William White in a 2008

Commonwealth Scientific and Industrial Research Organisation The Commonwealth Scientific and Industrial Research Organisation (CSIRO) is an Australian Government agency responsible for scientific research. CSIRO works with leading organisations around the world. From its headquarters in Canberra, CSIRO ...

(CSIRO) publication. It is named in honor of the late

shark Sharks are a group of elasmobranch fish characterized by a cartilaginous skeleton, five to seven gill slits on the sides of the head, and pectoral fins that are not fused to the head. Modern sharks are classified within the clade Selachimo ...

fishery 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 ...

biologist and conservationist Sid Cook. 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 ...

is a long adult male collected from the

Description

A small species growing to long, the Cook's swellshark has a stocky body and a short, broad head. The snout is flattened and rounded, with the

nostril A nostril (or naris , plural ''nares'' ) is either of the two orifices of the nose. They enable the entry and exit of air and other gasses through the nasal cavities. In birds and mammals, they contain branched bones or cartilages called turbi ...

s preceded by laterally enlarged flaps of skin that do not reach the mouth. The slit-like eyes are positioned high on the head and followed by 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, a genus of land snails in family Cyclophoridae Cycl ...

s. The long, narrow mouth lacks furrows at the corners and contains 50–61 tooth rows in the upper jaw and 49–62 tooth rows in the lower jaw; each tooth has a long central cusp and a pair of smaller lateral cusps. The upper teeth are exposed when the mouth is closed. The fourth and fifth 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 lie 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 and are shorter than the first three. The pectoral fins are rather small and angular, with nearly straight trailing margins. The two

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 have rounded apices; the first is much larger and taller than the second, originating over the back 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 ...

bases, while the second is positioned opposite the similarly-shaped but slightly larger

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 ...

. The pelvic fins are small and angular; males have very long

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 ...

. 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 se ...

is low, with a distinct lower lobe and a strong ventral notch near the tip of the upper lobe. The

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 are widely spaced, with three points and a median ridge. The dorsal coloration is distinctive, consisting of a grayish brown background with six pale-edged dark saddles along the body and two on the tail. The first saddle is curved forward, with its front edge intersecting each eye. There are pale dots on the snout and fins, and inside the saddles on the body. On the flanks, the dorsal coloration fades into the plain light gray of the underside.

Distribution and habitat

The Cook's swellshark is only found in the

, from the

Northern Territory The Northern Territory (commonly abbreviated as NT; formally the Northern Territory of Australia) is an states and territories of Australia, Australian territory in the central and central northern regions of Australia. The Northern Territory ...

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

to the

Tanimbar Islands The Tanimbar Islands, also called ''Timur Laut'', are a group of about 65 islands in the Maluku (province), Maluku Provinces of Indonesia, province of Indonesia. The largest and most central of the islands is Yamdena; others include Selaru to t ...

Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania between the Indian and Pacific oceans. It consists of over 17,000 islands, including Sumatra, Java, Sulawesi, and parts of Borneo and New Guine ...

. It resides in water deep.

Biology and ecology

Like other ''Cephaloscyllium'' species, the Cook's swellshark is capable of inflating itself as a defensive measure. Almost nothing is known of its natural history.

Human interactions

The conservation status of the Cook's swellshark has not been evaluated by 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).

References

{{Taxonbar, from=Q1950333 Cephaloscyllium Taxa named by Bernard Séret Taxa named by Peter R. Last Taxa named by William Toby White Fish described in 2008