Re: Paedomorphosis ( Re: BARYONYX' CLAWS )

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

<<Why would you find this so noteworthy? The present avian wing 
architecture is easily adaptable to underwater swimming, as penguins so 
obviously demonstrate. And back in the Triassic, the architecture of the 
avian wing--that is, the theropod forelimb and pectoral girdle--was 
considerably different, and much more adaptable to a grasping, predatory 
function. So--now we have dozens of species of penguins, and then we had 
dozens of species of predatory dinosaurs.>>


     Why would I find this noteworthy? Yes, the avian wing is very 
adaptable to underwater swimming. Why? Underwater swimming is basically 
the same as flight. It has the same motions, kinematics and uses the 
same muscles, flight apparatus, and control as flapping, aerial flight. 
Compare this to theropods. They did not have the same flight stroke ( 
couldn't even lift the humerus above the body ), they did not have the 
same kinematics ( most of the more basal theropods did not have the 
semilunate carpal, and all theropods lacked a single sternal unit, 
peg-like coracoids, a dorsolaterally facing glenoid, etc. ), most basal 
theropods do not show the same type of musclature, they do not show a 
comparable flight apparatus, and they did not have cerebellums modified 
for balance. So theropods as a whole do not show a bird-like flight 
apparatus. The main exceptions are the higher maniraptoriformes. However 
that they also lack many flight related features suggests that they did 
not evolve from flying ancestors and their birdlike features evolved for 
climbing, balance, etc. 

Speculation about the hypothetical " Triassic theropod flight apparatus" 
is very speculative. But, all speculation aside, a bird has to have 
several osteological features for flight.

1) Acute scapulacoracoid angle. 
2) Posteriorly facing coracoid with a peg-like or weakly strut-like 
shape.
3) Single sternum. 

These features all withstand the stresses of flight brought by the 
musclature. Bracing is absolutely essential for flight. Since all known 
theropods do not show these features it is unlikely that they modified 
the hypothetical "Triassic flight apparatus". 

MattTroutman

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