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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).
Sarcopterygii (/ ˌ s ɑːr k ɒ p t ə ˈ r ɪ dʒ i. aɪ /; from Ancient Greek σάρξ (sárx) 'flesh' and πτέρυξ (ptérux) 'wing, fin') — sometimes considered synonymous with Crossopterygii (from Ancient Greek κροσσός (krossós) 'fringe') — is a clade (traditionally a class or subclass) of vertebrate animals which includes a group of bony fish commonly referred to as lobe ...
Regeneration, many different unrelated species can grow new limbs, tail or other body parts, if body parts are lost. [202] [203] The Statocyst is a balance sensory receptor independently found in different organisms like: some aquatic invertebrates, including bivalves, [204] cnidarians, [205] echinoderms, [206] cephalopods, [207] and ...
Shark Anatomy (50693674756) The gill slits of a whale shark flaring as it expels water from its pharyngeal cavity. In the shark anatomy image, it depicts the beginning half of the shark, including the gills. The shark gills are especially important and were evolved from the chordate pharyngeal gill slits synapomorphy.
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 ...
The decline in amphibian and reptile populations has led to an awareness of the effects of pesticides on reptiles and amphibians. [176] In the past, the argument that amphibians or reptiles were more susceptible to any chemical contamination than any land aquatic vertebrate was not supported by research until recently. [176]
Currently, of the approximately 12,000 extant reptile species and sub-species, only about 100 of are classed as marine reptiles. [30] Except for some sea snakes, most extant marine reptiles are oviparous and need to return to land to lay their eggs. Apart from sea turtles, the species usually spend most of their lives on or near land rather ...
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 ...