The Triakidae or houndsharks are a
family
Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...
of
ground sharks, consisting of about 40
species
A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...
in nine
genera
Genus (; : genera ) is a taxonomic rank above species and below family as used in the biological classification of living and fossil organisms as well as viruses. In binomial nomenclature, the genus name forms the first part of the binomial s ...
. In some classifications, the family is split into two
subfamilies
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 botanical subfamily names with "-oideae", and zool ...
, with the genera ''
Mustelus
''Mustelus'', also known as the smooth-hounds, is a genus of sharks in the family (biology), family Houndshark, Triakidae. The name of the genus comes from the Latin word ''mustela'', meaning weasel. It should not be confused with the genus nam ...
'', ''
Scylliogaleus'' and ''
Triakis'' in the subfamily Triakinae, and the remainders in the subfamily Galeorhininae.
Houndsharks are distinguished by possessing two large, spineless
dorsal fin
A dorsal fin is a fin on the back of most marine and freshwater vertebrates. Dorsal fins have evolved independently several times through convergent evolution adapting to marine environments, so the fins are not all homologous. They are found ...
s, an
anal fin
Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported o ...
and oval eyes with
nictitating eyelids. They are small to medium in size, ranging from in adult length. They are found throughout the world in warm and temperate waters, where they feed on small fish and invertebrates on the seabed and in midwater.
Fossil records of this group date back to the
Cenomanian
The Cenomanian is, in the International Commission on Stratigraphy's (ICS) geological timescale, the oldest or earliest age (geology), age of the Late Cretaceous epoch (geology), Epoch or the lowest stage (stratigraphy), stage of the Upper Cretace ...
.
Genera
Houndsharks are classified into subfamilies and genera as follows:
[
* Galeorhininae ]Gill
A gill () is a respiration organ, respiratory organ that many aquatic ecosystem, aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow r ...
, 1862
** '' Furgaleus'' Whitley, 1951 (whiskery shark)
** '' Galeorhinus'' Blainville, 1816 (school shark)
** '' Gogolia'' Compagno, 1973 (sailback houndshark)
** ''Hemitriakis
''Hemitriakis'' is a genus of houndsharks in the family
Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms th ...
'' Herre, 1923
** '' Hypogaleus'' J. L. B. Smith
James Leonard Brierley Smith (26 September 1897 – 8 January 1968) was a South African ichthyology, ichthyologist, organic chemist, and university professor. He was the first to identify a taxidermied fish as a coelacanth, at the time thought t ...
, 1957 (blacktip tope)
** '' Iago'' Compagno & Springer
Springer or springers may refer to:
Publishers
* Springer Science+Business Media, aka Springer International Publishing, a worldwide publishing group founded in 1842 in Germany formerly known as Springer-Verlag.
** Springer Nature, a multinationa ...
, 1971
* Triakinae Gray
Grey (more frequent in British English) or gray (more frequent in American English) is an intermediate color between black and white. It is a neutral or achromatic color, meaning that it has no chroma. It is the color of a cloud-covered s ...
, 1851
** ''Mustelus
''Mustelus'', also known as the smooth-hounds, is a genus of sharks in the family (biology), family Houndshark, Triakidae. The name of the genus comes from the Latin word ''mustela'', meaning weasel. It should not be confused with the genus nam ...
'' H. F. Linck, 1790 (smooth-hound)
** '' Scylliogaleus'' Boulenger, 1902
** '' Triakis'' J. P. Müller & Henle, 1839
The following fossil genera are also known:
See also
*List of sharks
Shark is the naming term of all members of Selachimorpha suborder in the subclass Elasmobranchii, in the class Chondrichthyes. The Elasmobranchii also include rays and skates; the Chondrichthyes also include Chimaeras. The first shark-like chond ...
References
*
Cladogram reference
{{Authority control
Triakidae
Taxa named by John Edward Gray
Extant Cenomanian first appearances