Euselachii

Great white shark

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.

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.

Squatina squatina

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.

• Euselachii
  • Superorder Selachimorpha (sharks):
    • Carcharhiniformes - ground sharks
    • Heterodontiformes - bullhead sharks
    • Hexanchiformes - six- and sevengill sharks
    • Lamniformes - mackerel sharks
    • Orectolobiformes - carpet sharks
    • Pristiophoriformes - saw sharks
    • Squaliformes - dogfish
    • Squatiniformes - angel sharks
  • Superorder Rajomorphii or Batoidea (rays, torpedoes, sawfish and guitar fish):
    • Myliobatiformes - stingrays
    • Pristiformes - sawfish
    • Rajiformes - skates, sometimes in addition to guitarfish and wedgefish
    • Rhiniformes - wedgefish (frequently included in Rajiformes)
    • Rhinobatiformes - guitarfish (frequently included in Rajiformes)
    • Torpediniformes - electric rays
  • Euselachii incertae sedis[6]
    • †Ctenacanthiformes Cappetta 1988