Taillight shark
The taillight shark is a little-known species of dogfish shark
Squalidae is the family of dogfish sharks. They are found in the Atlantic, Pacific, and Indian oceans, from tropical equatorial climates to the Arctic and Antarctic....

 in the family Dalatiidae
Dalatiidae is a family of sharks in the order Squaliformes, commonly known as kitefin sharks . Members of this family are small, under long, and are found worldwide. They have cigar-shaped bodies with narrow heads and rounded snouts...

, and the only member
In biology, a monotypic taxon is a taxonomic group with only one biological type. The term's usage differs slightly between botany and zoology. The term monotypic has a separate use in conservation biology, monotypic habitat, regarding species habitat conversion eliminating biodiversity and...

 of its genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

. It is known from only two specimens collected from deep oceanic waters
Pelagic zone
Any water in a sea or lake that is not close to the bottom or near to the shore can be said to be in the pelagic zone. The word pelagic comes from the Greek πέλαγος or pélagos, which means "open sea". The pelagic zone can be thought of in terms of an imaginary cylinder or water column that goes...

 in the southern Atlantic Ocean
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...

. A small shark with a laterally compressed body and a bulbous snout, this species has unusual adaptation
An adaptation in biology is a trait with a current functional role in the life history of an organism that is maintained and evolved by means of natural selection. An adaptation refers to both the current state of being adapted and to the dynamic evolutionary process that leads to the adaptation....

s that indicate a specialized lifestyle: its pectoral fins are paddle-like and may be used for propulsion, unlike other sharks, and it has a pouch-like gland on its abdomen that emits clouds of luminescent
Bioluminescence is the production and emission of light by a living organism. Its name is a hybrid word, originating from the Greek bios for "living" and the Latin lumen "light". Bioluminescence is a naturally occurring form of chemiluminescence where energy is released by a chemical reaction in...

 blue fluid. This shark is likely aplacental viviparous and a formidable predator for its size. The International Union for Conservation of Nature (IUCN) presently lacks sufficient data to assess its conservation status.

Taxonomy and phylogeny

The first specimen of the taillight shark was collected by the Cape Town
Cape Town
Cape Town is the second-most populous city in South Africa, and the provincial capital and primate city of the Western Cape. As the seat of the National Parliament, it is also the legislative capital of the country. It forms part of the City of Cape Town metropolitan municipality...

 trawler Arum in 1963, and was initially identified as a longnose pygmy shark
Longnose pygmy shark
The longnose pygmy shark is a rare species of dogfish shark in the family Dalatiidae and the only member its genus. It is known only from a handful of specimens collected from the cold oceanic waters of the Southern Hemisphere, between the surface and a depth of...

 (Heteroscymnoides marleyi) before being recognized as a hitherto unknown species. The genus name Euprotomicroides comes from this shark's resemblance to the pygmy shark
Pygmy shark
The pygmy shark, Euprotomicrus bispinatus, the second-smallest of all the shark species after the dwarf lanternshark, is a sleeper shark of the Dalatiidae family, the only member of the genus Euprotomicrus...

 (Euprotomicrus bispinatus). The specific epithet zantedeschia is derived from Zantedeschia aethiopica
Zantedeschia aethiopica
Zantedeschia aethiopica ; syn. Calla aethiopica L., Richardia africana Kunth, Richardia aethiopica Spreng., Colocasia aethiopica Spreng...

, a species of arum lily for which the trawler Arum was named.

Phylogenetic analysis based on dentition
Dentition pertains to the development of teeth and their arrangement in the mouth. In particular, the characteristic arrangement, kind, and number of teeth in a given species at a given age...

 indicates that the taillight shark is the most basal member of its family, and is sister to the clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...

 containing all other dalatiid species. Although there are no definitive fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...

 remains, the taillight shark may have evolved in the early Paleocene
The Paleocene or Palaeocene, the "early recent", is a geologic epoch that lasted from about . It is the first epoch of the Palaeogene Period in the modern Cenozoic Era...

 epoch (65.5–55.8 Ma), as part of a larger adaptive radiation
Adaptive radiation
In evolutionary biology, adaptive radiation is the evolution of ecological and phenotypic diversity within a rapidly multiplying lineage. Starting with a recent single ancestor, this process results in the speciation and phenotypic adaptation of an array of species exhibiting different...

 of dogfish sharks into midwater habitats. The teeth of the extinct shark Palaeomicroides ursulae, found in early Campanian
The Campanian is, in the ICS' geologic timescale, the fifth of six ages of the Late Cretaceous epoch . The Campanian spans the time from 83.5 ± 0.7 Ma to 70.6 ± 0.6 Ma ...

 (83.5–70.6 Ma) deposits in Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

, closely resemble those of the taillight shark.

Distribution and habitat

The two specimens of the taillight shark were caught off South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...

 in a trawl operating at a depth of 458–641 m (1,500–2,100 ft), and off Uruguay
Uruguay ,officially the Oriental Republic of Uruguay,sometimes the Eastern Republic of Uruguay; ) is a country in the southeastern part of South America. It is home to some 3.5 million people, of whom 1.8 million live in the capital Montevideo and its metropolitan area...

 in a trawl operating at a depth of 195–205 m (640–670 ft). These records suggest that this shark is an inhabitant of the open ocean. However, it is unclear whether the known specimens were captured near the sea bottom where the trawls operated, or from midwater as the nets were being retrieved.


The taillight shark is laterally compressed, with a long, rounded snout and large, oval eyes. The mouth is large, containing 29 tooth rows in the upper jaw and 34 tooth rows in the lower jaw. The upper teeth are small and needle-like, while the lower teeth are large and triangular, with their bases interlocking to form a continuous cutting surface. The lips are thick and fringed, though not modified to be suctorial
Suctorial pertains to the adaptation for sucking or suction, as possessed by marine parasites such as the Cookiecutter shark, specifically in a specialised lip organ enabling attachment to the host....

. The 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 are large, and increase in size from the first to the last.

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 are rounded and lack spines; the first is smaller than the second and located about halfway between the pectoral and pelvic fins. The pectoral fins are enlarged into rounded paddles. The pelvic fins are small and originate at the level of the second dorsal fin; the anal fin is absent. The caudal fin has a strong lower lobe and a long upper lobe with a prominent notch near the tip. The body is covered by small, non-overlapping dermal denticles; each denticle has radial ridges converging to a round central pit. The body is dark brown above and black below, with light margins on the fins. There are small light-emitting photophore
A photophore is a light-emitting organ which appears as luminous spots on various marine animals, including fish and cephalopods. The organ can be simple, or as complex as the human eye; equipped with lenses, shutters, color filters and reflectors...

s scattered over the body. The first specimen was an immature female (originally reported incorrectly as a mature male) 17.6 cm (6.9 in) long, and the second was a mature male 41.6 cm (16.4 in) long.

Biology and ecology

The muscular, lobe-like pectoral fins of the taillight shark suggest that they may be used for propulsion, in a manner more akin to that of chimaera
Chimaeras are cartilaginous fish in the order Chimaeriformes, known informally as ghost sharks, ratfish , spookfish , or rabbitfishes...

s than other sharks, or at least for hovering in the water column. Its strongly built jaws and teeth likely allow it to tackle relatively large prey. On the belly in front of the cloaca
In zoological anatomy, a cloaca is the posterior opening that serves as the only such opening for the intestinal, reproductive, and urinary tracts of certain animal species...

, there is a pouch-like groove devoid of denticles and lined with a luminescent tissue formed into numerous tightly-packed papillae (nipple-like structures). The entrance to the pouch is a slit lined with folds of skin. In life, the pouch emits a glowing blue fluid of unknown function. Reproduction is presumably aplacental viviparous as in the other members of its family.

Human interactions

The taillight shark is not caught significantly by any fishery
Generally, a fishery is an entity engaged in raising or harvesting fish which is determined by some authority to be a fishery. According to the FAO, a fishery is typically defined in terms of the "people involved, species or type of fish, area of water or seabed, method of fishing, class of boats,...

, possibly due to its small size and habitat preferences. The International Union for Conservation of Nature (IUCN) does not yet have enough data to assess its conservation status beyond Data Deficient
Data 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 source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.