Dinosaur Ancestors and the Origins of Dinosaurs

Fame as a dinosaur paleontologist certainly would be justified for anyone who discovered the skeletal remains of the first dinosaurs. However, as shown by the discussion of amniote development, the phrase "first dinosaur" is in itself arguable in the light of evolutionary theory. After all, geologic ranges for fossil lineages are not always static. The possibility that fossils for ancestors of a hypothetical lineage have simply not been discovered yet leads to the concept of ghost lineages, meaning that a greater complement of ancestor and descendant species may still be locked away undiscovered in rocks somewhere in the world. For now, paleontologists can define the geologic range of dinosaurs as 228 to 65 Ma (Late Triassic through to the Late Cretaceous) on the basis of discovered specimens, but an understanding

FIGURE 6.10 Cast of the pterosaur Anhanguera from the Early Cretaceous of Argentina: Fernbank Museum of Natural History, Atlanta, Georgia. Anhanguera, alas, was also not a dinosaur.

FIGURE 6.10 Cast of the pterosaur Anhanguera from the Early Cretaceous of Argentina: Fernbank Museum of Natural History, Atlanta, Georgia. Anhanguera, alas, was also not a dinosaur.

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