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= Catshark   = Catsharks are ground sharks of the family Scyliorhinidae. They are one of the largest families of sharks with around 160 species placed in 17 genera. Although they are generally known as catsharks, many species are commonly called dogfish or gato. They feed on benthic invertebrates and smaller fish. Catsharks are not harmful to humans.

Anatomy and Appearance
Catsharks may be distinguished by their elongated, cat-like eyes and two small dorsal fins set far back. Most species are fairly small, growing no longer than 80 cm (31 in); a few, such as the nursehound (Scyliorhinus stellaris) can reach 1.6 m (5.2 ft) in length. Most of the species have a patterned appearance, ranging from stripes to patches to spots.

Characteristics of genus Apristurus are mostly dark bodies, having a long anal fin that ends in front of where the lower caudal fin begins. The snouts of the members of Apristurus are flat. They also present upper and lower labial furrows.

The sonic hedgehog dentition expression is first found as a bilateral symmetrical pattern and is found in certain areas of the embryonic jaw. Every 18-38 days the teeth are replaced as is a common characteristic of the developmental process of sharks

The "swell sharks" of the genus Cephaloscyllium have the curious ability to fill their stomachs with water or air when threatened, increasing their girth by a factor of one to three.

Some Catsharks, such as the chain catshark, are bioflourescent.

Distribution
Catsharks are found around seabeds in temperate and tropical seas worldwide, ranging from very shallow intertidal waters to depths of 2,000 m (6,600 ft) or more, such as the members of genus Apristurus  The Red spotted catshark lives in the shallower rocky waters ranging from Peru to Chile, and migrate to deeper waters during the winter months. They are usually restricted in small ranges. Juvenile and adult chain dogfish live on the soft or rocky bottom of the Atlantic from Massachusetts to Nicaragua. Adults tend to live on the soft sandy bottoms possibly due to egg deposition sites.

Genera[edit source
The family includes 17 genera and over 160 species making it one of the largest family of sharks.
 * Apristurus  Garman, 1913
 * Asymbolus  Whitley, 1939
 * Atelomycterus  Garman, 1913
 * Aulohalaelurus  Fowler, 1934
 * Bythaelurus  Compagno, 1988
 * Cephaloscyllium  T. N. Gill, 1862
 * Cephalurus  Bigelow and Schroeder, 1941
 * Figaro  Whitley, 1928
 * Galeus  Rafinesque, 1810
 * Halaelurus  T. N. Gill, 1862
 * Haploblepharus  Garman, 1913
 * Holohalaelurus  Fowler, 1934
 * Parmaturus  Garman, 1906
 * Pentanchus  H. M. Smith and Radcliffe in Smith, 1912
 * Poroderma  A. Smith, 1838
 * Schroederichthys  A. Smith, 1838
 * Scyliorhinus  Blainville, 1816

Cladogram

 * Scyliorhinidae
 * Scyliorhininae
 * Galeinae
 * Pentanchini
 * Galeini
 * Galeina
 * Halelaelurina
 * Atelomycterininae
 * Schroedericthyinae

Behavior
Some Catsharks do not undergo long distance migrations because they are bad swimmers. Due to being nocturnal, some species sleep close together in crevices throughout the day and then go hunting at night. Some species such as the small spotted catshark, Scyliorhinus canicula,are sexually monomorphic and exhibit habitat segregation, where males and females live in separate areas; males tend to live in open seabeds, while females tend to live in caves. Some species of catsharks may deposit egg cases in structured habitats, which may also act as nurseries for the newly hatched sharks.

Reproduction
Some species are aplacental viviparous. Many species of catshark, like the Chain Dogfish, are oviparous and lay large eggs in egg cases, called mermaid's purse and have curly tendrils at each end, for protection, onto the seabed. It takes almost a year for a catshark to hatch from the egg. Instead of laying the eggs and letting them sit for a year, some species of Catshark hold onto the egg until a few months before the shark hatches. Some catsharks exhibit ovoviviparity by holding onto the embryos until they are completely developed and then give live birth. Some species of catsharks mate by biting and holding the female’s pectoral fins and wrestle her into a mating position.

Aquaria[edit source
The Australian marbled catshark, Atelomycterus macleayi, is a favored type for home aquaria, because it rarely grows to more than 60 cm (2.0 ft) in length. The coral catshark, however, is the most common scyliorhinid in home aquaria.