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Sharks are found in all seas. They generally do not live in fresh water, with a few exceptions such as the bull shark and the river shark which can swim both in seawater and freshwater. [99] Sharks are common down to depths of 2,000 metres (7,000 ft), and some live even deeper, but they are almost entirely absent below 3,000 metres (10,000 ft).
Note that reptile-like amphibians, mammal-like reptiles, and non-avian dinosaurs are all paraphyletic. The placement of hagfish on the vertebrate tree of life has been controversial. Their lack of proper vertebrae (among with other characteristics found in lampreys and jawed vertebrates) led phylogenetic analyses based on morphology to place ...
Marine vertebrates are vertebrates that live in marine environments. These are the marine fish and the marine tetrapods (primarily seabirds, marine reptiles, and marine mammals). Vertebrates are a subphylum of chordates that have a vertebral column (backbone). The vertebral column provides the central support structure for an internal skeleton.
Found in all oceans [328] it was one of the largest and most powerful predators in vertebrate history, [327] and probably had a profound impact on marine life. [329] The Greenland shark has the longest known lifespan of all vertebrates, about 400 years. [330] Some sharks such as the great white are partially warm blooded and give live birth.
The first shark-like chondrichthyans appeared in the oceans 400 million years ago, [1] developing into the crown group of sharks by the Early Jurassic. [2] Listed below are extant species of shark. Sharks are spread across 512 described and 23 undescribed species in eight orders. The families and genera within the orders are listed in ...
Marine reptile. Marine reptiles are reptiles which have become secondarily adapted for an aquatic or semiaquatic life in a marine environment. Only about 100 of the 12,000 extant reptile species and subspecies are classed as marine reptiles, including marine iguanas, sea snakes, sea turtles and saltwater crocodiles. [1]
Active. Amphibian Species of the World 6.2: An Online Reference (ASW) is a herpetology database. It lists the names of frogs, salamanders and other amphibians, which scientists first described each species and what year, and the animal's known range. The American Museum of Natural History hosts Amphibian Species of the World, which is updated ...
Evolution of fish. The Devonian period (419–359 Mya), also known as the Age of Fishes, saw the development of early sharks, armoured placoderms and various lobe-finned fish, including the tetrapod transitional species. The evolution of fish began about 530 million years ago during the Cambrian explosion. It was during this time that the early ...