Thread: Descent of Birds

Is it odd that birds descend from saurischia (lizard hipped) and not ornithischia (bird hipped)?

It's probably a case of convergent evolution of hip structures and an historical accident of terminology (my guess).

Originally Posted by Zwirko

It's probably a case of convergent evolution of hip structures and an historical accident of terminology (my guess).

Your guess is correct:

"Oddly, birds are derived from the "lizard-hipped" dinosaurs and not from the "bird-hipped" ornithiscian dinosaurs. The "bird-hipped" condition of a pubis pointing toward the back of the animal occurred twice independently, once in the ornithischians and once in the lineage leading to birds, an example of convergent evolution. Thus "ornithischia," taken literally, is a misnomer, since the ornithischians have ornithischian-like pelves, not bird-like. Only birds (and their immediate ancestors) have bird-like pelves."

Source:
The Saurischia

and as with many characteristics, dromaeosaurs have modified the saurischian pelvis to become more bird-like :

The dromaeosaur pubis – ornithischian saurischians