Common sharks

from Wikipedia, the free encyclopedia
Common sharks
Leopard shark (Triakis semifasciata)

Leopard shark ( Triakis semifasciata )

Systematics
Subclass : Euselachii
Subclass : Plate gill (Elasmobranchii)
without rank: Sharks (selachii)
Superordinate : Galeomorphii
Order : Ground Sharks (Carcharhiniformes)
Family : Common sharks
Scientific name
Triakidae
Gray , 1851

The smooth sharks (Triakidae), also called raccoon sharks or dog sharks , are a family of ground sharks (Carcharhiniformes). They are divided into nine genera and over 45 species , 28 of which belong to the genus Mustelus .

features

They are small to medium-sized (maximum size: two meters) sharks. In contrast to other sharks, the very smooth skin (→ name), which is only covered by tiny skin teeth, is striking. Smooth sharks are usually gray or gray-brown in color, not patterned, with a lighter underside. The head has no laterally protruding edges. The eyes are oval and horizontal. They are usually twice as long as they are tall. There are injection holes but very small. The front nostrils have small flaps that are 2.5 to 3.2 times as wide as the nostrils. The labial folds on the mouth are very long. The teeth are small with 3 to 4 tips. They are in 43 to 60 rows in each jaw and are uniform in both pines. The teeth on the side do not form any comb-like rows. Smooth sharks have two thornless dorsal fins . The first is relatively small and lower than the upper lobe of the caudal fin . It is closer to the base of the pectoral fin than to the base of the pelvic fins . The radials of the pectoral fins are limited to the base of the fin. There are no pits on the tail fin stalk. The upper edge of the upper caudal fin lobe is always smooth. The lower lobe of the caudal fin is small or absent. The vertebral bodies have a wedge-shaped, central, ossified core. The spiral casing has 14 to 16 turns.

Smooth sharks reproduce ovoviviparously or viviparously . The placenta is spherical.

distribution

Great sharks live worldwide in tropical, subtropical and temperate latitudes in the shelf areas of all oceans. Almost no smooth shark lives in the open oceans; it is known that the dog shark can also live pelagically . One species, Iago omanensis , the smallest smooth shark at just 37 centimeters , can be found at depths of 2000 meters. The dog shark ( Galeorhinus galeus ), the gray shark ( Mustelus mustelus ) and the white-spotted shark ( Mustelus asterias ) live in European waters such as the North Sea , the Irish Sea , the English Channel , the Bay of Biscay and the Mediterranean Sea .

Systematics

Schnauzbarthai ( Furgaleus macki )
Dog shark ( Galeorhinus galeus )
White-spotted Smooth Shark ( Mustelus asterias )
Dark Smooth Shark ( Mustelus canis )
Star spot shark ( Mustelus manazo )

There are nine genera and 46 species:

literature

  • Leonard JV Compagno : FAO Species Catalog Vol. 4, Sharks of the World, An Annotated and Illustrated Catalog of Shark Species Known to Date. Part 2 - Carcharhiniformes, page 380, ISBN 92-5-101383-7
  • Joseph S. Nelson, Terry C. Grande, Mark VH Wilson: Fishes of the World. John Wiley & Sons, 2016, ISBN 978-1118342336

Web links

Commons : Smooth Sharks  - Collection of images, videos and audio files