1. claws -- a few modern birds have claws, but usually only as babies.
2. teeth -- no modern birds have teeth.
3. flat sternum (no keel) -- the only modern day birds with flat sterna are flightless birds.
4. concave articulation points on the cervical vertibrae instead of the standard elongated, saddle-shaped articulations that most birds have.
5.free vertebrae in the truck region rather than the typical fused vertebrae seen in all modern birds.
6. presence of abdominal ribs. these are found in theropods and other reptiles but not in any modern birds.
7. a ribcage which lacks uncinate processes and does not articulate to the sternum. all modern-day birds have strut-like uncinates and sternum articulations.
8. only 6 vertebrae in the sacrum. modern birds have 11 to 23.
9. mobile joints in not only the fingers, but also in the elbow and wrist. in modern birds, all of the joints have been fused.
10. downward-facing shoulder socket (like the kind found in other theropod dinosaurs) rather than the typical outward-facing shoulder sockets found in birds.
11. solid bones. the bones of birds are hollow and allow air to permeate them.
12. long bony tail with freely moving vertebra, just like the sorts of tails found in reptiles. birds today lack tails. (they only have "tails" made of feather, which aren't really, truly tails.) and the vertebrae they do have down there are of course fused.
13. the fenestrae in the skull are arranged the same way is in other theropods. the fenestrae in bird skulls are arranged much differently.
14. a short, heavy quadratic bone with a forward inclination.
15. there is a bend in the jawbone behind the tooth row.
16. presence of a long retro-articular process. this is very reptilian and found in no birds.
17. the jugal bone is straight and thin as in other reptiles.
18. a preorbital bar that saparates the anteorbital fenestra and the eye socket.
19. the occipital condyle and foraman magnum are located above the dorsal end of the quadrate (as in theropods), rather than below the quadrate (as in modern birds).
20. slender, elongated cerebral hemispheres which do not overlap the midbrain. in birds, the cerebral hemispheres are much heavier and extend past the midbrain.
------- wouldn't it just be easier to call archaeopteryx a "dinosaur with feathers"??
2006-10-14
12:22:22
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11 answers
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asked by
tobykeogh
3