''Cephaloscyllium'' is a
genus of
catsharks, and part of the
family Scyliorhinidae, commonly known as swellsharks because of their ability to inflate their bodies with water or air as a defense against
predators. These sluggish,
bottom-dwelling sharks are found widely in the
tropical and
temperate coastal waters of the
Indian and
Pacific Oceans. They have stocky, spindle-shaped bodies and short, broad, and flattened heads. The mouth is capacious, containing many small teeth and lacking furrows at the corners. The two
dorsal fins are placed far back on the body, with the first much larger than the second. Different species have various color patterns of saddles, blotches, reticulations, and/or spots. The largest members of the genus can grow over in length. Swellsharks prey on a variety of fishes and
invertebrates, and are
oviparous
Oviparous animals are animals that lay their eggs, with little or no other embryonic development within the mother. This is the reproductive method of most fish, amphibians, most reptiles, and all pterosaurs, dinosaurs (including birds), and ...
, with females producing
egg capsules in pairs. They are harmless and have been deemed of having no commercial value.
Taxonomy
The genus ''Cephaloscyllium'' was proposed by American
ichthyologist
Ichthyology is the branch of zoology devoted to the study of fish, including bony fish ( Osteichthyes), cartilaginous fish (Chondrichthyes), and jawless fish (Agnatha). According to FishBase, 33,400 species of fish had been described as of Octobe ...
Theodore Gill from the
Greek ''kephale'' ("head") and ''skylion'' ("dogfish"), in an 1862 issue of ''Annals of the Lyceum of Natural History of New York''.
However, most of Gill's contemporaries, particularly those in Europe, preferred to keep the swellsharks within the genus ''Scyllium'' (a
synonym
A synonym is a word, morpheme, or phrase that means exactly or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are all ...
of ''
Scyliorhinus''). ''Cephaloscyllium'' did not gain wide acceptance until
Samuel Garman
Samuel Walton Garman (June 5, 1843 – September 30, 1927), or "Garmann" as he sometimes styled himself, was a naturalist/zoologist from Pennsylvania. He became noted as an ichthyologist and herpetologist.
Biography
Garman was born in Indian ...
published "The Plagiostomia" in a 1913 volume of ''Memoirs of the Museum of Comparative Zoology'', in which he recognized three species: ''
C. isabellum'', ''
C. ventriosum'', and ''
C. umbratile''.
A long history of taxonomic confusion exists regarding the species within ''Cephaloscyllium'' owing to several factors, including variation in appearance (particularly between juveniles and adults), the existence of multiple undescribed species, a paucity of detailed scientific descriptions and
type material
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 ...
, and the use of unreliable characters. Until recently, various authors had recognized five to eight species, along with at least five undescribed species in Australian waters and more in the western central Pacific and the Indian Ocean.
In 2008, significant studies were made in resolving the taxonomy of ''Cephaloscyllium'', with a revision of the genus and an increase in the number of described species to 21.
Species
There are currently 17 recognized species in this genus:
* ''
Cephaloscyllium albipinnum
The whitefin swellshark (''Cephaloscyllium albipinnum'') is a little-known species of catshark, belonging to the family (biology), family Catshark, Scyliorhinidae, Endemism, endemic to southeastern Australia. It is found down, on the outer cont ...
''
Last, Motomura & W. T. White W. may refer to:
* SoHo (Australian TV channel) (previously W.), an Australian pay television channel
* ''W.'' (film), a 2008 American biographical drama film based on the life of George W. Bush
* "W.", the fifth track from Codeine's 1992 EP ''Bar ...
, 2008 (whitefin swellshark)
* ''
Cephaloscyllium cooki''
Last, Séret & W. T. White W. may refer to:
* SoHo (Australian TV channel) (previously W.), an Australian pay television channel
* ''W.'' (film), a 2008 American biographical drama film based on the life of George W. Bush
* "W.", the fifth track from Codeine's 1992 EP ''Bar ...
, 2008 (Cook's swellshark)
* ''
Cephaloscyllium fasciatum''
W. L. Y. Chan, 1966 (reticulated swellshark)
* ''
Cephaloscyllium hiscosellum
The Australian reticulate swellshark (''Cephaloscyllium hiscosellum'') is a little-known species of catshark in the family Scyliorhinidae. It is found off the coast of northwestern Australia at depths of . This shark has a stocky body and a sho ...
''
W. T. White W. may refer to:
* SoHo (Australian TV channel) (previously W.), an Australian pay television channel
* ''W.'' (film), a 2008 American biographical drama film based on the life of George W. Bush
* "W.", the fifth track from Codeine's 1992 EP ''Bar ...
& Ebert, 2008 (Australian reticulate swellshark)
* ''
Cephaloscyllium isabellum''
Bonnaterre, 1788 (draughtsboard shark)
* ''
Cephaloscyllium laticeps
The Australian swellshark (''Cephaloscyllium laticeps'') or draughtboard shark, is a species of catshark, and part of the family Scyliorhinidae, endemic to southern Australia. This bottom-dwelling species can be found on the continental sh ...
''
A. H. A. Duméril, 1853 (Australian swellshark)
* ''
Cephaloscyllium pictum''
Last, Séret & W. T. White W. may refer to:
* SoHo (Australian TV channel) (previously W.), an Australian pay television channel
* ''W.'' (film), a 2008 American biographical drama film based on the life of George W. Bush
* "W.", the fifth track from Codeine's 1992 EP ''Bar ...
, 2008 (painted swellshark)
* ''
Cephaloscyllium sarawakensis''
Ka. Yano, A. Ahmad & Gambang, 2005 (Sarawak pygmy swellshark)
* ''
Cephaloscyllium signourum''
Last, Séret & W. T. White W. may refer to:
* SoHo (Australian TV channel) (previously W.), an Australian pay television channel
* ''W.'' (film), a 2008 American biographical drama film based on the life of George W. Bush
* "W.", the fifth track from Codeine's 1992 EP ''Bar ...
, 2008 (flagtail swellshark)
* ''
Cephaloscyllium silasi''
Talwar, 1974 (Indian swellshark)
* ''
Cephaloscyllium speccum''
Last, Séret & W. T. White W. may refer to:
* SoHo (Australian TV channel) (previously W.), an Australian pay television channel
* ''W.'' (film), a 2008 American biographical drama film based on the life of George W. Bush
* "W.", the fifth track from Codeine's 1992 EP ''Bar ...
, 2008 (speckled swellshark)
* ''
Cephaloscyllium stevensi''
E. Clark & J. E. Randall, 2011 (Steven's swellshark)
* ''
Cephaloscyllium sufflans''
Regan
The family name Regan, along with its cognates O'Regan, O Regan, Reagan, and O'Reagan, is an Anglicized form of the Irish surname Ó Riagáin or Ó Ríogáin, from Ua Riagáin. The meaning is likely to have originated in ancient Gaelic ''ri'' ...
, 1921 (balloon shark)
* ''
Cephaloscyllium umbratile''
D. S. Jordan & Fowler, 1903 (blotchy swellshark)
* ''
Cephaloscyllium variegatum''
Last, Séret & W. T. White W. may refer to:
* SoHo (Australian TV channel) (previously W.), an Australian pay television channel
* ''W.'' (film), a 2008 American biographical drama film based on the life of George W. Bush
* "W.", the fifth track from Codeine's 1992 EP ''Bar ...
, 2008 (saddled swellshark)
* ''
Cephaloscyllium ventriosum''
Garman, 1880 (swellshark)
* ''
Cephaloscyllium zebrum''
Last, Séret & W. T. White W. may refer to:
* SoHo (Australian TV channel) (previously W.), an Australian pay television channel
* ''W.'' (film), a 2008 American biographical drama film based on the life of George W. Bush
* "W.", the fifth track from Codeine's 1992 EP ''Bar ...
, 2008 (narrowbar swellshark)
*
''Cephaloscyllium'' sp. 1 Not yet described (Philippine swellshark)
*
''Cephaloscyllium'' sp. not yet described (tiger swellshark)
*
''Cephaloscyllium'' sp. not yet described (New Guinea swellshark)
*
''Cephaloscyllium'' sp. not yet described (dwarf balloon shark)
*
''Cephaloscyllium'' sp. not yet described (dwarf oriental swellshark)
*
''Cephaloscyllium'' sp. not yet described (New Caledonia swellshark)
*
''Cephaloscyllium'' sp. not yet described (Red Sea swellshark)
Phylogeny and evolution
Morphological and
molecular phylogenetic
Molecular phylogenetics () is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominantly in DNA sequences, to gain information on an organism's evolutionary relationships. From these analyses, it is possible to ...
studies have shown the closest relative of ''Cephaloscyllium'' to be ''Scyliorhinus'', and these two genera and ''
Poroderma'' form the
subfamily
In biological classification, a subfamily (Latin: ', plural ') is an auxiliary (intermediate) taxonomic rank, next below family but more inclusive than genus. Standard nomenclature rules end subfamily botanical names with "-oideae", and zoologi ...
Scyliorhininae, the most
basal
Basal or basilar is a term meaning ''base'', ''bottom'', or ''minimum''.
Science
* Basal (anatomy), an anatomical term of location for features associated with the base of an organism or structure
* Basal (medicine), a minimal level that is nec ...
clade
A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...
of the
order
Order, ORDER or Orders may refer to:
* Categorization, the process in which ideas and objects are recognized, differentiated, and understood
* Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of d ...
Carcharhiniformes.
The oldest confirmed ''Cephaloscyllium''
fossils come from
Miocene epoch (23–5.3
Mya
Mya may refer to:
Brands and product names
* Mya (program), an intelligent personal assistant created by Motorola
* Mya (TV channel), an Italian Television channel
* Midwest Young Artists, a comprehensive youth music program
Codes
* Burmese ...
) deposits in
California,
though based on the rate of
DNA divergence in sharks, the swellshark lineage likely dates back to the
Cretaceous period (145.5–65.5 Mya).
Distribution and habitat
''Cephaloscyllium'' is widely distributed in the Indian and Pacific Oceans, in
temperate and
tropical waters, but not close to the
equator
The equator is a circle of latitude, about in circumference, that divides Earth into the Northern and Southern hemispheres. It is an imaginary line located at 0 degrees latitude, halfway between the North and South poles. The term can als ...
. Swellshark diversity is greatest around
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 ...
and in the west-central Pacific, where multiple
endemic species are found. The most far-flung members of the genus are
''C. sufflans'' off southeastern Africa,
''C. silasi'' off southwestern
India,
''C. umbratile'' in the northwestern Pacific, and
''C. ventriosum'' along the western coast of the
Americas
The Americas, which are sometimes collectively called America, are a landmass comprising the totality of North and South America. The Americas make up most of the land in Earth's Western Hemisphere and comprise the New World.
Along with th ...
.
One
hypothesis states ''Cephaloscyllium'' originally evolved in Australia and
New Guinea, and subsequently dispersed outwards in a series of colonization events, eventually reaching Africa and the Americas.
''Cephaloscyllium'' species,
bottom-dwelling sharks, can be found from the
intertidal zone
The intertidal zone, also known as the foreshore, is the area above water level at low tide and underwater at high tide (in other words, the area within the tidal range). This area can include several types of habitats with various species o ...
to a depth of on upper
continental and insular slopes.
Description

Swellsharks are stocky and spindle shaped, with the trunk tapering substantially to the
caudal peduncle. The head is short (comprising less than a fifth of the total length), broad, and flattened. The snout is very short and blunt, with the
nostrils preceded by laterally enlarged flaps of skin. The eyes are horizontally oval or slit-like and placed high on the head, with cat-like
pupils and rudimentary
nictitating eyelids. A broad ridge occurs beneath each eye, and a
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 ...
behind. The mouth is very large and wide, containing numerous small, multicusped teeth; the upper teeth are exposed when the mouth is closed (except in
''C. silasi''). No furrows are found at the corners of the mouth.
The
pectoral fins are generally large and broad, and 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. The two
dorsal fins are placed far back on the body: the first dorsal fin originates behind 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 ...
origins, while the second dorsal fin is positioned about opposite 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 se ...
. The first dorsal and anal fins are much larger than the second dorsal fin. The tail is short; the
caudal fin is broad with a distinct lower lobe and a strong ventral notch near the tip of the upper lobe. The skin is thick and covered by well-
calcified 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. The coloration is typically grayish or brownish, with a variety of patterns that include saddles, blotches, reticulations, and/or spots.
In several species, the juveniles differ substantially in coloration from the adults. ''Cephaloscyllium'' species generally fall into two size groups: dwarf species include
''C. fasciatum'' and
''C. silasi'', which are under long, and large species include
''C. umbratile'' and
''C. ventriosum'', which may exceed in length.
Biology and ecology
Members of the genus ''Cephaloscyllium'' are generally slow-moving, sedentary animals with an anguilliform (
eel-like) mode of swimming.
Of the species whose diets have been documented, they have been known to feed on a wide variety of benthic organisms, including other
sharks and rays,
bony fish
Osteichthyes (), popularly referred to as the bony fish, is a diverse superclass of fish that have skeletons primarily composed of bone tissue. They can be contrasted with the Chondrichthyes, which have skeletons primarily composed of cartilag ...
es,
crustaceans, and
mollusc
Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is esti ...
s.
Swellsharks are perhaps best known for their ability to inflate themselves by rapidly swallowing water or air when threatened; this behavior may allow them to wedge themselves inside crevices, make themselves harder to swallow, and/or intimidate a would-be predator. Reproduction is
oviparous
Oviparous animals are animals that lay their eggs, with little or no other embryonic development within the mother. This is the reproductive method of most fish, amphibians, most reptiles, and all pterosaurs, dinosaurs (including birds), and ...
, with females producing two eggs at a time, one in each
oviduct. Individual eggs are enclosed in a flask-shaped
capsules with tendrils at the corners that allow them to be attached to underwater structures.
Human interactions
Swellsharks are harmless to humans and generally of no economic value, but are susceptible to being caught as
bycatch
Bycatch (or by-catch), in the fishing industry, is a fish or other marine species that is caught unintentionally while fishing for specific species or sizes of wildlife. Bycatch is either the wrong species, the wrong sex, or is undersized or juve ...
in
artisanal and
commercial fisheries.
Several species (e.g. ''C. umbratile'' and ''C. ventriosum''), are known to be extremely hardy, capable of surviving out of water for extended periods and adapting readily to captivity.
References
{{Taxonbar, from=Q2510308
Shark genera
Taxa named by Theodore Gill