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Re: Dinosaurs and birds



Scott Hartman wrote-

It had sure better be. Outside of the assymetrical feathers (which is a drag-reducing adaptation, not a lift-generating one, although the two are related) there isn't any terribly good reason to assume Archaeopteryx was volant. It _may_ have been, but it would have to get around the glenoid not being oriented for completel upstrokes, the lack of an ossified sternum for hypertrophied musculature attachment, the lack of a pulley-like supracoracoideus needed to prevent dislocation of the humerus during downstrokes, and some problems with the wings (you'll hear more around SVP time).

What does Sapeornis bring to this issue? It didn't have an ossified sternum either, and its short coracoid (shorter than most other maniraptorans in fact) and reduced acromion process suggest its supracoracoideus was even less flight-adpated than Archaeopteryx, correct? Yet it has huge arms with a well developed deltopectoral crest and reduced manual digit III. Do you believe Sapeornis was flightless too?


T. Michael Keesey wrote-

Maybe he never threw his full support behind it, but:

"More interesting is to consider the possibility that sauropods are basal to
all other dinosaurs, that prosauropods and ornithischians are sister groups,
and that theropods are a sister group to the prosauropod+ornithischian group.
This is what the feet say, anyway."
(from http://dml.cmnh.org/2002Aug/msg00030.html)

Just to clarify, "what the feet say" was in reference to the amount of phalanges on pedal digit V, which Olshevsky finds to be incapable of increasing through evolution. Thus sauropods must be basal to even early dinosauromorphs like Silesaurus and Lagerpeton, because they sometimes have two phalanges on digit V. Crazy single character analyses...


Mickey Mortimer