Diapsids

Diapsids ("two arches") are a group of tetrapods that developed two holes (temporal fenestra) in each side of their skulls about 300 million years ago during the late Carboniferous period. Living diapsids are extremely diverse, and include all crocodiles, lizards, snakes, tuataras, and birds. Although some diapsids have lost either one hole (lizards), or both holes (snakes), or have a heavily restructured skull (modern birds), they are still classified as diapsids based on their ancestry. At least 7,925 species of diapsid reptiles exist in environments around the world today (nearly 18,000 when birds are included).

Taxonomy

• Subclass DIAPSIDA
  • Order Araeoscelidia
  • Order Avicephala (polyphyletic)
  • Order Younginiformes (paraphyletic)
  • Order Hupehsuchia
  • Order Thalattosauria
  • Superorder Ichthyopterygia (ichthyosaurs and grippidians)
    • Order Grippidia
    • Order Ichthyosauria
  • (unranked) Sauria
    • Infraclass Lepidosauromorpha
      • Order Eolacertilia
      • Superorder Lepidosauria (tuataras, lizards, amphibaenians, and snakes)
        • Order Sphenodontia (tuatara and extinct relatives)
        • Order Squamata (lizards, snakes, and amphibaenians)
      • Superorder Sauropterygia (plesiosaurs and relatives)
        • Order Placodontia
        • Order Nothosauroidea
        • Order Plesiosauria
    • Infraclass Archosauromorpha
      • Order Aetosauria
      • Order Choristodera
      • Order Phytosauria
      • Order Prolacertiformes
      • Order Pterosauria
      • Order Rauisuchia
      • Order Rhynchosauria
      • Order Trilophosauria
      • Superorder Crocodylomorpha (crocodilians and extinct relatives)
        • Order Crocodylia (crocodylians)
        • Order Mesosauria
        • Order Notosuchia
        • Order Protosuchia
        • Order Sphenosuchia
        • Order Tethysuchia
      • Superorder Dinosauria (including birds)
        • Order Ornithischia
        • Order Saurischia (including birds)
          • Class Aves (birds)