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Re: Exaptation

In a message dated 95-12-07 21:10:21 EST, dchwang@itsa.ucsf.EDU (Dennis C
Hwang) writes:

>Just a thought here--weren't pterosaurs already fully accomplished fliers 
>by the late Triassic?  I seem to recall that _Preondactylus_, 
>_Peteinosaurus_, and some others had already made a strong showing by 
>this point (?_Eudimorphodon_).
>If this is the case, then evolving protobirds weren't necessarily 
>expanding into a whole new set of *unoccupied* niches by developing 
>flight.  Perhaps secondary flightlessness appears so commonly (by BCF) 
>because of competition with pterosaurs, who may have already been 
>occupying those niches.
>Flight is, after all, pretty expensive metabolically.  One might well 
>imagine that it would be lost pretty quickly if it confers little 
>survival advantage.

This is indeed a possible cause of secondary flightlessness. Pterosaurs were
flying around the Late Triassic with no problem.