Euselachii

Euselachii are an infraclass of a class of cartilaginous fish. This group includes sharks and rays.[2][3][4]

Euselachii
Temporal range:
Silurian-Holocene[1]
Tiger shark
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Elasmobranchii
Infraclass: Euselachii
Hay, 1902
Orders

See text

Taxonomy

Of the 14 orders that compose Euselachii, 8 belong to the sharks, 6 to the rays, without an intermediate taxon separating sharks of rays. For this reason, some authors have separated Euselachii in two:

super-order Selachimorpha corresponding to orders of sharks; super-order Rajomorphii corresponding to the orders of rays, torpedoes, sawfish and guitar fish. For those who do not recognize these two super-orders, Euselachii therefore has for synonyms Pleurotremata, Selachimorpha and Rajomorphii.

Reproduction

Both oviparity and viviparity are found in Euselachii. Around 70% of sharks are viviparous,[5] including some members of Carcharhiniformes such as requiem sharks and hammerhead sharks, while the remaining 30% of sharks as well as all rays are either oviparous or ovoviviparous.

Physical appearance

There was a recent discovery that a Palaeozoic chondrichthyan (carcharopsis) was found to no longer resemble the "triple-layer" tooth structure that the modern day chondrichthyan sharks model.

List of orders

References

  1. "Infraclass Euselachii Hay 1902". Fossilworks.org.
  2. Nelson, J. S. (2006). Fishes of the World (4 ed.). Hoboken, NJ: John Wiley & Sons. p. 49. ISBN 978-0-471-25031-9.
  3. "Euselachii". Integrated Taxonomic Information System. Retrieved 21 May 2018.
  4. "Fish glossary". FishBase.
  5. "Mating and Reproduction of Sharks", Shark Foundation
  6. J. A. Long. 2011. The Rise of Fishes: 500 Million Years of Evolution (Second Edition) 1-287 [G. Lloyd/G. Lloyd/M. Uhen]
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