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Skull diapsida 1 svg

Generalised diapsid skull

Diapsids (Diapsida) (meaning "two arches") are a group of sauropsids ("reptiles") that include crocodiles, lizards, snakes, tuataras, and birds as well as many extinct forms like non-bird dinosaurs, pterosaurs, non-crocodilian pseudosuchians and many Mesozoic sea reptiles like plesiosaurs and ichthyosaurs.

One of the diapsid characteristic is that they have two holes (temporal fenestra) in each side of their skulls behind the eye. The holes are there for jaw-muscles to give diapsids more powerful bite. Some diapsid lineages have lost one or both of the fenestrae but they are still known to be diapsids because of their other features.

Diapsid groups[]

  • Araeoscelidia
  • Ichthyopterygia (ichthyosaurs and grippidians)
    • Grippidia
    • Ichthyosauria (ichthyosaurs, fish shaped sea reptiles)
  • Weigeltisauridae (gliding early reptiles: Coelurosauravus etc.)
  • Testudines (turtles)
  • Lepidosauromorpha
    • Eolacertilia
    • Lepidosauria
      • Sphenodontia (tuatara and relatives)
      • Squamata (lizards, snakes, and amphisbaenians)
        • Mosasauroidea (mosasaurs (giant sea lizards) and relatives)
    • Sauropterygia (plesiosaurs and relatives)
      • Placodontia (placodonts)
      • Nothosauroidea
      • Plesiosauria (plesiosaurs)
  • Archosauromorpha
    • Protorosauria
    • Rhynchosauria (rhynchosaurs, odd looking plant-eaters)
    • Trilophosauria
    • Phytosauria (phytosaurs)
    • Archosauria (archosaurs)
      • Pseudosuchia (pseudosuchians, crocodile-line archosaurs)
        • Ornithosuchidae
        • Suchia
          • Aetosauria (aetosaurs, plant eating armored crocs)
          • Rauisuchia (rauisuchians)
      • Avemetatarsalia
        • Scleromochlus
        • Ornithodira