Galeomorphi is a superorder of

shark Sharks are a group of elasmobranch cartilaginous fish characterized by a ribless endoskeleton, dermal denticles, five to seven gill slits on each side, and pectoral fins that are not fused to the head. Modern sharks are classified within the ...

s. They are sometimes called galea or galean sharks. There are about 300 living

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 23 families. Galean sharks are divided into four orders: the Heterodontiformes, Orectolobiformes,

Lamniformes The Lamniformes (, from Greek ''lamna'' "fish of prey") are an order (biology), order of sharks commonly known as mackerel sharks (which may also refer specifically to the family Lamnidae). It includes some of the most familiar species of sharks, ...

, and Carcharhiniformes. The extinct, enigmatic Synechodontiformes are presently placed by some authors in the galeomorphs, but their taxonomic position still remains uncertain.

Classification

Order Heterodontiformes

The bullhead sharks are a small order of basal modern

s ( Neoselachii). All are relatively small, with the largest species being just in adult length. They are bottom feeders in tropical and subtropical waters. They appear in the fossil record in the Early

Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately 143.1 Mya. ...

, well before any of the other galean sharks. However, they have never been common, and it is likely their origin lies even further back. There are nine living species in a single genus, ''Heterodontus'' and a single family. * Family Heterodontidae (Bullhead sharks)

Order Orectolobiformes

Carpet sharks are another small order of sharks, so called because many members have ornate patterns reminiscent of carpets. Sometimes the term "carpet shark" is used interchangeably with wobbegong, which are a subgroup of the order. Carpet sharks have two dorsal fins, without spines, and a small mouth that is forward of the eyes. Many have barbels and small gill slits, with the fifth slit overlapping the fourth. The upper lobe of the caudal fin tends to be mostly in line with the body, while the lower lobe is poorly developed. The order has around 43 species in 7 families and 13 genera: * Family Brachaeluridae Applegate (Blind sharks) * Family Ginglymostomatidae

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 (Nurse sharks) * Family Hemiscylliidae

, 1862 (Bamboo sharks) * Family Orectolobidae

, 1896 (Wobbegong sharks) * Family Parascylliidae

, 1862 (Collared carpet sharks) * Family Rhincodontidae ( J. P. Müller & Henle, 1839) (Whale sharks) * Family Stegostomatidae

, 1862 (Zebra sharks)

Order Lamniformes

Mackerel sharks are an order which includes some of the most familiar species of sharks, such as the

great white shark The great white shark (''Carcharodon carcharias''), also known as the white shark, white pointer, or simply great white, is a species of large Lamniformes, mackerel shark which can be found in the coastal surface waters of all the major ocea ...

, as well as more unusual representatives, such as the goblin shark and the megamouth shark. Members of the order are distinguished by possessing two dorsal fins, 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 ...

, five gill slits, eyes without nictitating membranes, and a mouth extending behind the eyes. Mackerel sharks may also refer specifically to the family Lamnidae. The order includes seven families and sixteen living species: * Family Alopiidae Bonaparte, 1838 (Thresher sharks) * Family Carchariidae Müller & Henle, 1839 (Sand tiger sharks) * Family Cetorhinidae

, 1862 (Basking sharks) * Family Lamnidae J. P. Müller and Henle, 1838 * Family Megachasmidae Taylor, Compagno & Struhsaker, 1983 (Megamouth shark) * Family Mitsukurinidae D. S. Jordan, 1898 * Family Odontaspididae Müller & Henle, 1839 (Sand sharks) * Family Pseudocarchariidae Compagno, 1973 (Crocodile shark) * Family Cretoxyrhinidae (Extinct) * Family Otodontidae (Extinct)

Order Carcharhiniformes

Ground sharks are the largest order of sharks, and include a number of common types such as the blue shark, catsharks, swellsharks and sandbar sharks. Members of the orders are characterized by the presence of a nictitating membrane over the eye, two dorsal fins, an

, and five

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 ...

slits. The families in the order Carcharhiniformes are expected to be revised; recent

DNA Deoxyribonucleic acid (; DNA) is a polymer composed of two polynucleotide chains that coil around each other to form a double helix. The polymer carries genetic instructions for the development, functioning, growth and reproduction of al ...

studies show that some of the traditional groups are not

monophyletic In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent co ...

. The order includes eight families and over 270 species: * Family Carcharhinidae (Requiem sharks) * Family Hemigaleidae (Weasel sharks) * Family Leptochariidae (Barbeled houndshark) * Family Proscylliidae (Finback catsharks) * Family Pseudotriakidae (False catsharks) * Family Scyliorhinidae (Catsharks) * Family Sphyrnidae (Hammerhead sharks) * Family Triakidae (Houndsharks)

References

External links

* . Database of bibliography of living/fossil sharks and rays (Chondrichtyes: Selachii) with more than 15.000 listed papers and many download links. {{Taxonbar, from=Q47969 Elasmobranchii Chordate superorders