Evolution and Diversity of Reptiles

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Skull Morphology

  • reptile groups are assessed using skull morphology
    • anapsids don't have any holes in their skull except the orbit
    • synapsids have a single fenestra as well as the orbit
    • diapsids have two fenestrae as well as the orbit
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Evolution of Reptiles

  • reptiles first appeared around 315 million years ago, evolving from amphibians
  • reptiles are tetrapods
    • Tetrapoda split into sauropsids and synapsids during the Carboniferous (Sauropsida contains reptiles)
  • reptiles are amniotes
    • the first amniotes appeared in the late Carboniferous 
  • Diapsida is a clade of Sauropsida, and contains Lepidosauria and Archosauria
    • Lepidosauria contains Squamata and Rhynchocephalia
    • Archosauria contains Crurotarsi and Avemetatarsalia
  • two main phylogenetic groups within Reptilia:
    • Archosauromorpha; containing crocodiles, turtles, pterosaurs and dinosaurs
    • Lepidosauromorpha; containing squamates, rhynchocephalians, ichthyosaurs, and plesiosaurs 
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Diversity of Modern Reptiles

  • Testudines; contains 14 families of turtles
  • Crocodylia: contains 3 families of crocodilians
  • Squamata: contains 41 families of lizards and amphisbaenians and 25 families of snakes
  • Rhycnhocephalia; contains as single species, known as the tuatara (Sphenodon punctatus
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