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RE: Bird reduce their "heating bills" in cold climates



Furthermore, scales and feathers can co-occur on the same body parts: 
http://elibrary.unm.edu/sora/Condor/files/issues/v032n01/p0064-p0065.pdf
 
It's entirely possible polar dinosaurs grew a coat of dinofuzz/feathers over 
the scales to keep warm during the dark winters, and seasonally shed this 
insulation when summer approached.
 
Most birds have scales on the metatarsi, but willow ptarmigans have a coat of 
feathers which covers the scales, and this feather coat is seasonally shed from 
the ventral portion of the feet:  
http://elibrary.unm.edu/sora/Condor/files/issues/v079n03/p0380-p0382.pdf
 
Some theropods also had feathered metatarsi:
http://www.nature.com/nature/journal/v461/n7264/full/nature08322.html

Guy Leahy
----------------------------------------
> Date: Mon, 5 Jul 2010 17:51:30 -0700
> From: tijawi@yahoo.com
> To: dinosaur@usc.edu
> CC: tijawi@yahoo.com
> Subject: Re: Bird reduce their "heating bills" in cold climates
>
> Jura wrote:
>
>
>> You are oversimplifying here. "Saurischians" is really
>> "maniraptors and a couple of non-maniraptoran coelurosaurs.
>> The majority of known saurischian integument is scaly.
>
>
> I don't see why this is a "one-or-the-other" situation. Scaly integument and 
> dino-fuzz could co-exist in coelurosaurs (and other dinosaurs). After all, 
> modern birds have scales on their feet and on part of the face.
>
>
> There is no reason why feathers (and their precursors) should have replaced 
> scales. This what Xu et al. had to say about _Dilong_:
>
> "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)."
>
>
> Further, in many Yixian dinosaurs, the filamentous integument (feathers or 
> dino-fuzz) is preserved as a halo around the body. Scales are not preserved 
> on the body itself - even on parts of the body where we would expect to see 
> scales (such as the feet, or face). This also applies to _Archaeopteryx_. So 
> the absence of scales is a preservational artifact, and so should not be used 
> as a guide as to whether scales were present or absent in real life. This is 
> what Xu et al. were alluding to.
>
>
>> Assuming that all these fossils are preserving rea
> at
>> filamentous integument evolved on four separate occasions
>> (coelurosaurs close to Maniraptora, Hypsilophodontids,
>> _Psittacosaurus_, Pterosaurs), rather than the 7+
>> re-evolutions of a scaly covering that would be required if
>> it was a symplesiomorphy.
>
>
> The above scenario strikes me as highly *non-parsimonious*. It assumes that 
> scaly integument is lost when filamentous integuments appeared. However, the 
> evidence suggests that a scaly covering was never actually lost - instead, 
> filamentous integument first appeared alongside scales, and the former 
> subsequently spread over the body at the expense of the latter.
>
>
>
> Cheers
>
> Tim
>
>
>
>