Paedomorphosis ( Re: BARYONYX' CLAWS )

["Matthew Troutman" <m_troutman@hotmail.com>]

>It is not clear that _all_ avian flightlessness evolved via 
>paedomorphosis.


  Au contaire! Many ornithologists ( Feduccia, Olson ) have speculated 
along these lines, and lets just face it, all of the flightless 
characteristics seen in flightless birds are paedomorphic 
characteristics. From the suboscine tapaculos to paleognathus ratites to 
gruiform island rails the sole factor that can be used to describe 
similiarity between the groups is their paedomorphic characters. The 
flat, sternum, the massive and disproportionate hindlimbs, the body 
proportions, the lowering the basal metabolic rate, and "furry" plumage 
can all be explained by paedomorphosis. Since most or all flightless 
birds have these characteristics, I find it safe to assume that 
paedomorphosis is the factor that makes birds flightless. There is no 
other factor that can account for all of these features. 

It comes full circle now : birds become isolated or occupy a new 
teresstrial niche, need to fly reduces, and paedomorphosis turns to 
selective advantage. 

Matt Troutman

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