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"The X Digit"...a Pteroid bone??



Thrs,Jan 21, 1999Raymond Thaddeus C. Ancog wrote:


>Well, what about the other features of the skeleton that would preclude
>pterosaurs from giving rise to birds? When the total evidence is weighed,
>the evidence against such a link far outweighs that for a link (many of
>which can be explained away as similar adaptation for flight).

I see many similarities in Pterosaur and Bird anatomy,...far too much to be
passed off as convergent evolution.
The whole development of the Supracoracoideus structure seems (to me) much
too complex to have developed twice independantly in two
separate lineages. As far as the rest of the skeleton, ...just what are we
comparing?? I propose an early branching (Triassic) of the Pterosaur-bird
line.
Pterosaurs would have had time enough to specialize and develope their more
bulky frames. My proposed missing link would have a furcula as well as a
long 4th
wing digit (although much shorter than later Pterosaurs). At any rate, it
would overall have been small and light enough not to have made hard
landings involving the forepaws.

>An aberrant carpal in birds? First time I've heard of that. The only living
>tetrapod I know of with such a feature is the giant panda. What exactly did
>these embryologists say?

I`m going to have to get a hold of the original papers myself (by Holmgren
1955 and Montagna 1945). My copy from the Archie Conference only shows dark
blurs where these limb elements should be.
This seems to be the embryological evidence that leads Feduccia (and others)
to outright reject a direct connection between dinosaurs and birds, and has
led them to proclaim that the three digits in birds are correctly referred
to as digits two, three, and four. ....I`m a bit behind the times, having
just read this article (from 1985) for myself. Evidently the research goes
back much further. I wonder if more research has been done since on this
topic...to refute these claims?? I doubt it as last I heard, Feduccia was
still making claims for the count of 2,3,4.