The whitefin dogfish (''Centroscyllium ritteri'') is a species of deep-sea

dogfish shark Squalidae, more commonly known as dogfish, dog sharks, or spiny dogfish, are one of several families of sharks categorized under Squaliformes, making it the second largest order of sharks, numbering 119 species across 7 families. Having earned t ...

in the family Etmopteridae. It has only been found in the northwest Pacific Ocean off the southeastern coast 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 ...

, between the latitudes of 35 and 32°N. It inhabits continental slopes and

seamount A seamount is a large geologic landform that rises from the ocean floor that does not reach to the water's surface (sea level), and thus is not an island, islet or cliff-rock. Seamounts are typically formed from extinct volcanoes that rise abru ...

s at a depth of . Reproduction is ovoviviparous. It is of no interest to

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 ...

and almost nothing is known of its biology. 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 ...

''ritteri'' is in honor of Dr. William Emerson Ritter of the University of California. The largest known example of this shark measured long. It has an elongated body with a broad, flattened head and a moderately long snout. The

eye Eyes are organs of the visual system. They provide living organisms with vision, the ability to receive and process visual detail, as well as enabling several photo response functions that are independent of vision. Eyes detect light and conv ...

s and

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 are large. The mouth is broadly arched, containing many teeth with narrow cusps and lateral cusplets. There are two roughly equal-sized dorsal fins with grooved spines; the second spine is longer than the first and slightly curved. The pectoral fins are short and broad, not reaching the first dorsal fin base when folded back. 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 are small and placed forward of the second dorsal fin. There is no

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 caudal peduncle is long, leading to an asymmetrical caudal fin. This shark is distinctive in being the only ''Centroscyllium'' species with abrupt black markings beneath its head, trunk, and pectoral fins, with a black stripe running from under the caudal peduncle to over the pelvic fins. These markings are in fact concentrations of tiny light-emitting photophores. Unusually, this shark also has photophores along the undersides of its upper eyelids. What function these structures could serve is unclear; Tchernavin speculated that they could be used to illuminate prey or stimulate the eye. The rest of the body is gray-brown, with white fin margins. There are numerous small cone-shaped, hooked prickles over the body, except for under the snout.

References

{{Taxonbar, from=Q2414954 Centroscyllium Taxa named by David Starr Jordan Taxa named by Henry Weed Fowler Fish described in 1903