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Re: Sinosauropteryx tail colors
Yup.. completely agree about the "critical mass" aspect and the
coexisting of different types of integument. Only makes sense,
especially in regards to how Xu et al frame it (I've seen others state
similar and have used the elephant analogy myself).
I have no idea where I came across the feathers and Juravenator...
Might have been one of those "it's 3am and I can't sleep" zombie
nights and I misread something.... probably the collagen/musculature
fibers. Either way, finding only a few tiny patches of scales,
especially in the regions where they were located, doesn't rule out
Juravenator having had filamentous feathers of one variety or another.
On Mon, Feb 1, 2010 at 6:55 PM, Tim Williams <firstname.lastname@example.org> wrote:
> Kris Kripchak <email@example.com> wrote:
>> Tim, so how do you interpret Juravenator? If memory serves, patches
>> of fossilized Juravenator skin (from the tail base and hind
>> leg) shows primarily scales... but I think I remember reading
>> something about how there may be traces of simple, filamentous feathers
>> present as well.
> If the _Juravenator_ specimen preserves feathers (even filamentous ones, or
> 'protofeathers'), then it is not mentioned by Gohlich and Chiappe (2006).
> This study states that feathers were not preserved. The tail does preserve
> fibers, but these are interpreted as either hypaxial musculature or
> subcutaneous collagen bundles.
>> I also think that Xu considered it most likely
>> that Juravenator and other feathered dinosaurs simply possessed
>> more extensive scales on their bodies than modern birds.
> I agree - and there is no reason why feathers (and their precursors) should
> have replaced scales. This is mentioned in the description of _Dilong_,
> where Xu et al. (2004) state:
> "Large, derived tyrannosauroids were reported to have scaled skin
> (28), but the presence of two kinds of body covering is not
> unexpected. However, current understanding of the integumentary
> morphology in non-avian theropods is hindered by poor information
> on distribution. Given the diverse morphologies of integumentary
> structures in living birds, it is possible that non-avian
> theropods had different integumentary morphologies on different
> regions of the body, and derived, large tyrannosauroids might bear
> both scale-like and filamentous integumental appendages.
> Alternatively, the lack of filamentous integumentary structures in
> derived tyrannosauroids is correlated with the large size, a
> physiological strategy also adopted by some mammals such as
> elephants, which lose most of their body hairs as they mature
> (29). This therefore supports the hypothesis that the original
> function of protofeathers is correlated with thermoregulation
> 5 years later, I think this still holds true. Feathers could theoretically
> co-exist with scales over much of the body. However, a certain 'critical
> mass' of feathers over most of the body (especially the trunk) would be
> needed in order for them to serve effectively in insulation.