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Re: Pterosaurs and ABSRD (sensu Williams)



In a message dated 5/20/01 1:01:30 PM EST, luisrey@ndirect.co.uk writes:

<< Should be clear by now that this is not any evolutionary step towards a 
true feather. >>

Longisquama "feathers" were probably not on the evolutionary path toward true 
feathers, but they could very well be structures that evolved independently, 
along a different path, from earlier dermal structures that did evolve into 
feathers in theropods.

I suspect some Permian and Triassic prolacertiforms, among which several 
lineages are well known to have been arboreal climbing and gliding reptiles, 
already had such dermal structures. In pterosaurs, these developed into a 
hairy coat; in certain archosaurs, these developed into scutes; in other 
archosaurs, these developed into true feathers. The protein in feathers would 
have had a multitude of uses, just as hair in mammals developed into 
fingernails and claws, glyptodont armor(??), armadillo shells, rhino horns, 
and pangolin scales.