zoo 201 amniotes NOT COMPLETE

  1. What is an amniotic egg?
    • 3 new membranes (amniote synapomorphy)
    • 1. amnion: surrounds developing embryo and holds it in amniotic fluid. keeps embryo moist and protects it
    • 2. chorion: outer membrane surrounds embryo and yolk, gas exchange with porous shell
    • 3. allantois: repository for nitrogenous waste
  2. Other Derived characteristics of Amniotes
    • Keratinized skin resistant to water loss
    • hardened nails or claws
    • lungs with greater internal surface area are filled by thoracic expansion (instead of buccal pumping)
    • no larvae or metamorphosis
    • loss of lateral line system
    • further loss/reduction of skull elements
  3. When did amniotes originiate and what are the 3 major groups?
    • Carboniferous (based on skull morphology)
    • 1. anapsids
    • 2. diapsids
    • 3. synapsids
  4. Anapsida characteristics
    • no temporal skull opening behind orbits (completely roofed by dermal skull bones)
    • turtles tradtionally considered anapsids, but now considered derived diapsids based on new data
  5. Diapsida characteristics
    • two temporal skull openings behind orbits (separated by bony arch)
    • represented today by all living reptiles (traditionally minus turtles) & birds
  6. Diapsida: Lepidosauria
    • all modern reptiles except crocodylians and turtles
    • tuataras (most basal lineage) lizards, snakes, amphisbaenians
    • >95% of living non-avian reptiles
  7. Diapsida: Archosauria
    • corcodylians, birds & extinct groups (e.g. pterosaurs, dinosaurs)
    • flight evolved twice in Archosauria (pterosaurs and birds)
  8. What kind of group are reptiles?
    Paraphyletic, because birds are not included
  9. Turtles on the phylogenetic tree
    • position under revision
    • some data indicate relationship close to archosaurs (DNA)
    • other data say closer to lepidosaurs (morphology)
  10. Synapsida characteristics
    • one temporal skull opening behind orbits
    • first linage to diverge from ancestral amniotes (basal to all other amniotes)
    • gave rise to mammal lineage (only extant lineage)
  11. Characteristics of Class Reptilia
    keratinized epidermal scales
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zoo 201 amniotes NOT COMPLETE
aminote power point in lappins half of zoology 201.