Great White Shark ( Carcharodon carcharias )
|Devon to this day|
|Bonaparte , 1838|
The plate gill (Elasmobranchii, synonym : Neoselachii), also called shark and ray-like , are a sub-class of cartilaginous fish (Chondrichthyes). They include the modern sharks (Selachii) and rays (Batomorphi) with around 1150 recent species . About 30 species live mainly in fresh water, the rest in the sea .
The plate gills differ from their sister group , the sea cats (Holocephali), by the five to seven gill slits without gill covers and the tooth strips in which the teeth are permanently replaced, from various shark-like cartilaginous fish groups known only in fossil form. a. by the strong restriction of the notochord , by the calcification of the vertebrae , the fusion of parts of the belt skeletons and the type of skin teeth .
The plate gills were traditionally divided into sharks and rays according to their external appearance. In 1996, the Neoselachi of de Carvalho and Shirai were divided independently of one another according to morphological characteristics into two monophyletic taxa , the Galeomorphii (Galea near Shirai), which mainly include large, open-water sharks, and the Squalea , which includes many bottom-dwelling sharks, deep-sea sharks and the rays belong. The sharks are thus merely a paraphyletic form taxon.
In the meantime, however, there are several molecular biological studies that confirm a basic dichotomy between sharks and rays. The morphological correspondences of the squalomorphic sharks with the rays then developed convergent . Since the rays, like the modern sharks, can be traced back to the fossil record since the early Jurassic , an ancestry of the rays at the end of a long evolutionary line of the Squalea is not supported by paleontological data.
The following table shows one version of each of the two different concepts of the internal systematics of Elasmobranchii.
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- CJ Underwood: Diversification of the Neoselachii (Chondrichthyes) during the Jurassic and Cretaceous. Paleobiology, 32 (2) (2006). pp. 215-235. PDF