Re: Life of Birds (vertical running)

["Ken Kinman" <kinman@hotmail.com>]

David Marjanovic wrote:
> Brooding is used as an explanation for the evolution of _wing_ feathers 
> (rectrices -- primaries and secondaries), not that of feathers in general 
> (whatever protofeathers, contour feathers...).  I for my part wouldn't try 
> to mix these up.  Insulation is still a very good reason why feathers, _if_ 
> they didn't start on the whole body, are found all over it in all 
> sufficiently known feathered animals.
******************************************
     I don't think I am mixing these up at all.  I see no reason why the 
earliest brooding feathers couldn't have been on the tail and rump area of 
the animal (perhaps on the abdomen as well).  A dorsal layer of contour 
feathers (in tracts) could provide waterproofing as well as an upper layer 
of insulation, under which were more ventral layers (not necessarily in 
tracts) of downier feathers directly in contact with the eggs or hatchlings.
    Evolutionary spreading of feathers forward on the body (to accomodate 
bigger clutches) could have improved internal thermoregulation so that 
cooler and cooler habitats could be colonized.  And then with 
thermoregulatory/brooding feathers on the arms, the advantages of 
wing-assisted incline running could have developed.
    All of this would have happened in the Triassic, with improvements in 
powered flight occurring throughout the Jurassic.  Most  
posteriorly-feathered "dinobirds" may have died out before the Cretaceous.  
However, that "porcupine-tailed" psittacosaur could provide some indication 
of what may have happened back in the Triassic (and I didn't even know about 
that specimen when I began proposing my FTF---feathered tails 
first----hypothesis).
    Anyway, I will not be surprised if we discover a number of 
posteriorly-feathered dinosaurs in the future.
               --------Ken Kinman
P.S.  And as I have said before, the Triassic forms which first developed 
feathers could have been facultatively bipedal  non-dinosauromorphs, and 
therefore the end of the tail would be expendable as a predator evasion 
strategy without causing lethal balancing problems.

_________________________________________________________________
Get your FREE download of MSN Explorer at http://explorer.msn.com/intl.asp