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Re: Fwd: Eodromaeus, new basal theropod from Triassic in Argentina

--- On Sun, 1/16/11, Matthew Martyniuk <martyniuk@gmail.com> wrote:

> From: Matthew Martyniuk <martyniuk@gmail.com>
> Subject: Fwd: Eodromaeus, new basal theropod from Triassic in Argentina
> To: "DML" <dinosaur@usc.edu>
> Date: Sunday, January 16, 2011, 11:42 PM
> One example that's often overlooked
> is _Caudipteryx_. Some specimens
> preserve scales on the ventral manual digits. Obviously,
> these
> coincide with the advanced-stage feathers anchored to the
> dorsal part
> of the same digits.


Unless you read something I didn't Zhou and Wang (2000) stated that they found 
evidence of skin impressions; not scales. No mention of scales was given in the 
paper, nor was it reflected in the diagram the authors provided of the 
skeleton. The most useful thing about the skin impression was that it gave one 
an idea of how large the digits were in life.


> Jason has used evo-devo to argue that feathers and scales
> *are*
> mutually exclusive many times before but this is easily
> falsified by
> looking at a number of fossil specimens. Even if feathers
> do
> "highjack" the developmental pathways used by scales, and
> even if the
> tarsal scutes (which are different from scales) of birds
> are actually
> modified feathers, there is plenty of proof that it's not
> an
> all-or-nothing trade. Feathers or filaments can and did
> coincide with
> typical dinosaurian scales in a number of specimens from
> all up and
> down the coelurosaurian tree, so there's no reason to think
> this
> couldn't be true of more basal taxa.


I'm assuming you are referring to _Scansoriopteryx/Epidendrosaurus_ and 
_Juravenator_. Both are specimens in which the alleged feather/scale 
association is present, but both are also highly ambiguous examples. For 
_Scansoriopteryx/Epidendrosaurus_ the authors mentioned that the scale 
impression by the tail was not found in "articulation" with the tail and had 
likely migrated from the tarsometatarsal region.

As for _Juravenator_, despite claims that the specimen preserves filaments 
under UV light, Chiappe and Goehlich's paper specifically states that what they 
found *might* be filaments. There preservation is slight, and only the tips are 
preserved. While they might be filaments, they might also just be preparation 
artifacts (sadly the figure they enclosed does not really show much of 
anything, though I suspect that this was bound to happen given the 

You might think this a bit nit-picky of me, but compare any of these guys with 
something like NGMC-91 where we can clearly see where there were filaments and 
where there were scales. The case is hardly as clear cut for any of the above 
mentioned guys.

Also, as an aside: there is more than one type of scale (just like how there is 
more than one type of feather). Avian tarsal scutes are scales.