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Re: AW: Heterodontosaurid with protofeathers



As a Bakker fan when a child, (and with an endothermy-liking bias) I
was recently afraid of supposing all dinosaurs were insulated when
there appeared the hairy tailed Psitaccosaurus. More so being so many
scaly patches of skin in hadrosaurs, Carnotaurus, I think there was
some sauropod, etc.

But now, and after Don Ohmes cites the pterosaur "hairs", I think, why
cannot these "hairs" be an ornithodiran apomorphy? After all, birds
have feathers and at the same time scales in the metatarsal region of
the hindlimb. Why cannot it be that all dinosaurs inherited hairs,
retaining also scales, and that when you get larger, the hair recedes
and the scales expand (because of avoiding overheating).

I know however, not only large dinosaurs have to be hairless, and
there iis not evidence of hair in scaly dinosaurs yet.

2009/3/18, don ohmes <d_ohmes@yahoo.com>:
>
>
>> --- On Wed, 3/18/09, evelyn sobielski
>> <koreke77@yahoo.de> wrote:
>
>> > The really interesting question here - and it is one
>> that
>> > is likely to be swamped by a deluge of faux-feather
>> > What is the use of such
>> integumentary
>> > structures? It is hard to see them as evolutionary
>> neutral,
>> > so they are likely to have conferred some benefit.
>> What
>> > precisely did it evolve for?
>
>> Camouflage, among other things. In my view, camouflage is
>> the best-guess for the 'original benefit'. The thing
>> about camo is, it's benefits can accrue at any moment in
>> the lifespan, and irregardless of climate, age, sex, or
>> dietary preference. Nor is there any associated behavioral
>> requirement.
>>
>> Also, any odd structure that serves to change the
>> silhouette or conceals the texture of edible (or dangerous)
>> skin-covered muscle has immediate function, unlike the
>> frequently cited insulation, which requires both extensive
>> coverage and thermal effect.
>>
>> Don
>
> I believe it is also worth noting that small-to-midsize predators logically
> accrue 'camo-benefit' in two of life's critical tasks, resource acquisition
> and predator avoidance. In terms of incremental evo-scenarios, it seems
> logical that these structures would be most likely to appear in this kind of
> animal (as opposed to herbivores, which have no need to sneak up on their
> food).
>
> Don
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