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giant birds

Dinogeorge wrote:

"However you care to arrange these taxa, the common ancestral forms of 
these taxa and birds were almost certainly capable of flying--and the 
closer the common ancestral form was to Archaeopteryx, the better flier 
it probably was. Archaeopteryx didn't acquire the power of flight 
overnight (the miracle that the "ground-up" theorists wish us to 
swallow) but evolved it much more gradually through a succession of 
those less flightworthy forms that were also the common ancestors of 
the various theropod groups and birds."

The above is a summary of what is referred to on the list as BCF. The 
recent systematic literature (e.g. Sereno 1999, Xu et al. 1999) seems 
(to me anyway) to contradict BCF. It is clear to me how phylogenetic 
schemes are constructed, but I don't understand the reasoning behind 
BCF. What is the rationale for BCF? The above statement from Dinogeorge 
seems to suggest a functional hypothesis based on the acquisition of 
flight. Functional hypotheses have been widely accepted yet proved 
wrong in the past (e.g. the evolution of the tetrapod limb - Coates and 
Clack 1991), so to make sure I was being fair to BCF I thought I'd 
raise the question.

Kendall Clements

Kendall Clements