Re: Paedomorphosis ( Re: BARYONYX' CLAWS )

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

>> Now, if in theropods, they needed to use their forelimbs for 
>>predation : why wouldn't they lose flight the typical avian way          
>>( paedomorphosis ) and tweak their forelimbs to work the way it >>does 
in phorusrhacids ? ( in which flight was lost the typical avian >>way 
and the forelimbs was modified ).

<<Perhaps they did it in just this way. But theropods were not typical 
avians, because at the time theropods began to appear, typical avians 
were still well in the future. So all bets are off as to the details of 
the mechanism whereby they became flightless, ground-dwelling forms. Not 
having evolved all the gear that birds have for powered flying doubtless 
gave theropods considerably more leeway in the mechanisms available to 
them for becoming secondarily flightless. By the time you're a 
full-fledged bird, the quickest route to flightlessness can only be 
paedomorphosis.>>

     This assuming that they had flighted ancestors. What can only 
totally diagnose that an animal is secondarily flightless is ancestry. 
But since the fossil record is rather sparse, we do not have the 
ancestors and we have to look at other ways to decide whether any 
theropods are secondarily flightless. Whether an dinosaur is not a 
typical bird in anatomy is not the point. Flight is only possible 
through certain adaptations in musculature and osteology. And when an 
dinosaur shows these features then it can be considered a bird. And 
since early birds that we know are more similiar to modern birds in 
architecture, then the same process of losing flight must apply. There 
are no other ways ( unless you still consider that the way penguins, 
auks, and plotopterids lost their aerial flight is valid; all this 
proves is that aqutic birds that use their forelimbs for swimming lost 
their flight in this way) .

MattTroutman

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