Reptiles

• Tetrapods


  Terrestrially adapted egg
• Amniotes


  Group of tetrapods whose extant members are the reptiles (including birds) and mammals

  
• Derived Characters of Amniotes


  • Amniotic eggs
  • Amnion
  • Chorion
  • Yolk Sac
  • Allantois

  
• Amniotic egg


  • Key evolutionary innovation for terrestrial life
  • Allowed the embryo to develop on land in its own private "pond", hence reducing the dependence of tetrapods on an aqueous environment for reproduction

  
• The first amniotes evolved from their amphibian ancestors

  Approximately 340 million years ago during the Carboniferous period

  
• The key differences between the synapsids, anapsids, and diapsids are the structures of the skull and the number of temporal fenestrae behind each eye
• Skull structures

  • Anapsids have no temporal fenestrae
  • Synapsids have one
  • Diapsids have two
• Traditionally, dinosaurs were considered slow, sluggish creatures
• Fossil discoveries and research have led to the conclusion that many dinosaurs were agile and fast moving

  
• Reptiles


  • Tuataras
  • Lizards
  • Snakes
  • Turtles
  • Crocodilians
  • Plesiosaurs
  • Ichthyosaurs

  
• Reptiles


  • Unlike amphibians, have scales that contain the protein keratin
  • Most lay their shelled eggs on land
  • Fertilization must occur internally, before the eggshell is secreted
  • Many species of snakes and lizards are viviparous

  
• Cold-blooded


  Ectothermic, but they do regulate their body temperature by using behavioral adaptations
• Lepidosaurs


  • One surviving lineage is represented by two species of lizard-like reptiles called tuataras, endemic to New Zealand
  • The other major living lineage consists of the lizards and snakes, or squamates, the largest order of reptiles

  
• Turtles


  • Have a boxlike shell made of upper and lower shields that are fused to the vertebrae, clavicles (collarbones), and ribs
• Crocodilians


  Alligators and crocodiles, belong to a lineage that reaches back to the late Triassic