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Re: New here, General Qs



--- Bradley Fischer <fischb22@hotmail.com> wrote:
>
> On a different topic: In a fairly recent issue of Scientific American, there 
> is an article about the evolution of feathers and their beginnings on 
> theropods. The article suggests that even T-rex probably was feathered.  
> Only problem I have with this theory is that the subject sample is all from 
> china and they found no large theropods with feathers. Anyone care to 
> comment on this? Am I off on my thinking?

I don't see why them all being from a certain place would have any bearing on
the matter. The feathered Liaoning specimens represent a wide variety of
coelurosaurian lineages.

They found no large theropods with feathers (unless you count _Beipiaosaurus_,
at about 2m in length -- I wouldn't) because there are no large theropods from
that locality, or any other deposit that preserves feathers (AFAIK).

Feathery integument is likely but not certain for _Tyrannosauroidea_.
_Sinosauropteryx_ is the most basal form known to have feathery integument (but
probably not true feathers), and _Tyrannosauroidea_ probably lies just outside
the most exclusive clade that includes it and other feathered Liaoning forms.
If feathery integument evolved at the latest possible point, given the current
data, _Tyrannosauroidea_ would not have been feathery, but it is more likely
that such integument originated earlier within _Tetanurae_ (or possibly outside
_Tetanurae_???).

(It's also worth noting that one specimen assigned to _Sinosauropteryx_ has
been claimed to be of a more basal neotetanuran, which would pretty much make
feathery tyrannosauroids a certainty.)

So feathery integument is *probably* (not certainly) a basal trait for
_Tyrannosauroidea_. But you can still have your featherless _T. rex_, if you
hypothesize that it had secondarily lost its integument due to large size, much
as large therians like elephants, rhinoceri, etc. have lost nearly all of their
fur.

Still, even if this is the case, there is an important difference between
therians and dinosaurs -- dinosaurs lay eggs. No matter how big they grow, all
dinosaurs hatch small. Therefore, even if adult _T. rex_ had lost much or all
of their integument, the hatchlings would probably still have had it.

But, until we find some Liaoning tyrannosauroids, we won't know for certain....

=====
=====> T. Michael Keesey <keesey@bigfoot.com>
=====> The Dinosauricon <http://dinosauricon.com>
=====> BloodySteak <http://bloodysteak.com>
=====> Instant Messenger <Ric Blayze>
=====

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