RE: Phil Currie celebration, tyrant skin, and other things

[Jura <archosaur@reptilis.net>]

--- "Tim Williams" <twilliams_alpha@hotmail.com>
> wrote:
>
>Tom Holtz wrote:
>
>>2) Tyrannosaurid juveniles may have been feathered; tyrannosaurid adults
>>may
>>have had feathers over part of their body, but these parts haven't been
>>recovered.  (Not very compelling argument, but at present only tiny scraps
>>of skin smaller than a CD case have been found).
>
>I actually regard this possibility as the most credible - especially if (as
>seems likely) feathers originally evolved for the purpose of thermal
>evolution.  An adult _Tyrannosaurus_, tipping the scales at 8 tonnes, may
>quite simply not have needed feathers.  Perhaps adult tyrannosaurs did
>retain a sprinkling of feathers over certain parts of the body, but just for
>the purpose of decoration or display rather than for insulation.

+++++++++++++++++++++++++++++++++++++++

I'm getting this overwhelming sense of deja-vu :)

If _T.rex_ started off downy and then lost it into adult-hood, would it not be 
more logical (if not more parsimonious) to assume that it was bare-skinned as 
an adult. In order for the above scenario to work, _T.rex_ would have to lose 
one type of integument and grow an entirely new piece in its place. Besides 
being expensive to do, energy wise, it would be the first time this type of 
thing has ever been recorded for a vertebrate.

__________________________________________

>I think we can confidently predict that feathers evolved in small theropods
>(_Ornitholestes_-size or below), not large ones.  The very much reduced
>surface area to volume ratio of an adult tyrannosaur reduced the need to
>minimize endogenous heat dissipating from the body.  Tyrannosaur chicks
>(being rather small) may have had downy feathers, but lost them at maturity.
>  Maniraptoriform taxa that only achieved a small adult body size kept their
>feathery coast throughout life.

++++++++++++++++++++++++++++

Does that mean we should/could expect a secondary loss of "fuzz" from the 
larger theriznosaurs as well?

____________________________


>>3) Tyrannosaurids may have had feathered ancestors, but had reversed to the
>>ancestral condition.

>A fourth possibility is that feathers were seasonal: grown before winter and
>shed before the arrival of warmer weather.  Of course, this depends upon
>whether tyrannosaurs actually ventured into colder habitats.

+++++++++++++++++++++++++++++

Again, this would seem to make more sense only if tyrannosaurs were bare 
skinned animals. The above scenario would be both extremely unique and 
extremely wasteful for the animal.

I mean, at least with the ontogenetic one, tyrannosaurs only had to do it once.

Jura - who believes choice 1 makes the most sense right now.


==
The Reptipage at: http://reptilis.net

Because reptiles are just cooler.

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