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Sedentary, bottom-dwelling sharks generally use buccal pumping to move water over to their gills compared to more active sharks, who will use ram ventilation and swim to force water to their mouth and gills. Most sharks can switch between these mechanisms as the situation requires depending on the abundance of oxygen in the water.
They and their close relatives, the sharks, compose the subclass Elasmobranchii. Rays are the largest group of cartilaginous fishes, with well over 600 species in 26 families. Rays are distinguished by their flattened bodies, enlarged pectoral fins that are fused to the head, and gill slits that are placed on their ventral surfaces.
Some authors consider it as equivalent to Neoselachii (the crown group clade including modern sharks, rays, and all other descendants of their last common ancestor). Other authors use the name Elasmobranchii for a broader branch-based group of all chondrichthyans more closely related to modern sharks and rays than to Holocephali (the clade ...
While the shark is moving, water passes through the mouth and over the gills in a process known as "ram ventilation". While at rest, most sharks pump water over their gills to ensure a constant supply of oxygenated water. A small number of species have lost the ability to pump water through their gills and must swim without rest.
Some sharks are so flexible, they can bend right around and touch their tails with their snouts. Shark skin is so rough that in the past it was used to make a type of sandpaper, called shagreen. Without their fins, sharks wouldn’t be able to stay the right way up. They’d roll over in the water. Most sharks never close their eyes.
Carpet sharks are sharks classified in the order Orectolobiformes / ɒ r ɛ k ˈ t ɒ l ə b ɪ f ɔːr m iː z /. Sometimes the common name "carpet shark" (given because many species resemble ornately patterned carpets ) is used interchangeably with "wobbegong", which is the common name of sharks in the family Orectolobidae .
Now in its 13th season, "Shark Tank" gives entrepreneurs the opportunity to pitch their companies to some of the most successful business people in the world. These "Sharks" invest their own money ...
The following outline is provided as an overview of and topical guide to sharks: Sharks (superorder Selachimorpha) are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 440 million years ago, before the time of the dinosaurs. [1]