The Evolution of Dinosaurs

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Fig. 1. Temporally calibrated phylogeny of Dinosauria, showing known temporal durations (solid bars), missing ranges (shaded bars), and ranges extended by fragmentary or undescribed specimens (dashed bars).  [View Larger Version of this Image

Fig. 2. Phylogeny of Dinosauria, showing the relationships among ornithischians (left) and saurischians (right).  [View Larger Version of this Image]

Fig. 3. Skeletal innovation in the three major clades of dinosaurs (Ornithischia, Theropoda, and Sauropodomorpha) as shown by contemporaneous species from the Upper Jurassic (Kimmeridgian) Morrison Formation of North America.  [View Larger Version of this Image]

  Fig. 4. Major stages in the evolution of modern avian skeletal design and function.  [View Larger Version of this Image]

Fig. 5. Dinosaurian paleobiogeography. (A) Temporally calibrated areagram showing the breakup of Pangaea into 10 major land areas by the end of the Cretaceous. Checkered bars indicate high-latitude connections that may have persisted into the Late Cretaceous. Five paleogeographic reconstructions (91) divide continental areas (outlines) into dry land (black) and shallow (epieric) seas (unshaded). (B) Continent-level vicariance hypothesis for the carcharodontosaurids Acrocanthosaurus, Giganotosaurus, and Carcharodontosaurus, which lived on North America, South America, and Africa, respectively, approximately 90 to 110 Ma. (C) Polar dispersal across Beringia (double-headed arrow) must be invoked to explain the geographic distribution of ceratopsians and other dinosaurian subgroups during the Late Cretaceous.  [View Larger Versions of these Images]