This is something that's been bugging me for a few days now - the avian group is usually associated with the Theropoda, which is an off-shoot from the lizard-hipped Saurischia. The Ornithischia are always depicted as a widely separate branch, yet the earliest known dinosaurs are Theropods (Eoraptor, Herrerrasaurus, etc), so isn't is more likely that the bird-like hip evolved once and that the common ancestor of (for instance) birds and hadrosaurs is closer than the common ancestor of birds and sauropods as the diagrams usually suggest? Or am I missing something here and the likelihood of the hips evolving twice are much greater than they seem?
2007-03-11
13:27:41
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3 answers
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Anonymous