GEOL 104 Dinosaurs: A Natural History

Fall Semester 2006
Evolution of the Vertebrates II

Review basic amniote anatomy.

Three main divisions within Amniota, each recognized by various synapomorphies but named after pattern of temporal fenestrae:

  • Synapsida, with infratemporal fenestra only
  • Anapsida, with no temporal fenestrae (symplesiomorphy)
  • Diapsida, with both infra- and supratemporal fenestra
    Cladistic studies place Anapsida and Diapsida as sister taxa within Reptilia.

    Division between synapsids and reptiles and (within reptile) between diapsids and anapsids in Pennsylvanian (late Paleozoic Era); oldest true archosaurs in Early Triassic Epoch.

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    Last modified: 14 July 2006