Re: AW: Heterodontosaurid with protofeathers

[evelyn sobielski <koreke77@yahoo.de>]

> > What
> precisely did it evolve for?
> 
> If they actually evolved FOR something, they should at
> least give us a good idea what the stimuli for it was (NOTE
> - I'm pretty sure this "anticipated adaptations" train of
> thought is not how evolution actually works).

Me neither - I meant "for" as in "fulfilling some purpose that inceases 
survivability and proliferation". It is clear that many evolutionary changes 
serve some purpose, but that purpose is only clear in hindsight. Mutation rolls 
the dice, selection picks the ones it likes. It picks according to some 
parameters, but the parameters are generally unknown to the mutation process.

"Anticipated adaptations" exist (cf dynamics of antibiotics resistance plasmid 
gain/loss in a bacterial population for example), but they are by no means 
dominant in evolution, because they are technically very hard to perform except 
on a very crude level.

However - and that is something that might warrant more study here - there are 
situations where the genetic framework for some apomorphic change is incipient 
but not realized, to a point that minor mutations are sufficient to make the 
change realize itself.

In a nutshell, I'd rather tend towards the assumption that "protofuzz" evolved 
near the base of Coelurosauria and perhaps more than once (probably more than 
once? what is more parsimonious here - multiple origins or multiple losses? It 
has to be one of these, AFAIK) , than towards the assumption that it evolved 
near the base of Archosauria once. Essentially, I would favor the hypothesis 
that some aspects of the underlying genetic framework are plesiomorphic for at 
least part of Archosauria, but that the realized phenotypic trait is not. (This 
is testable)

Also, the term "protofeathers" implies that the stuff evolved into feathers. 
Which for ornithischians is just baseless speculation at this time.


Regards,

Eike