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Re: "The X Digit"...a Pteroid bone??
Larry Febo wrote:
>The whole development of the Supracoracoideus structure >seems (to me) much
too complex to have developed twice >independantly in two separate lineages.
No structure (at least no structural analog) is too complex, in theory, to be
reproduced through convergence and/or parallelism. Certainly the development
of the supracoracoideus in avians is no more complex than their evolution of
endothermy, which, assuming there isn't an avain/mammal connection hidden in
the woodpile, would require that endothermy was developed independantly in
each group. Another example, cranial kinesis. It appears not only in avians
(and possibly nonavian theropods), but, independantly, in squamates, and
surely required a much more complex series of evolutionary steps than would
the independant development of superficially similar flight musculature in
birds and pterosaurs.