[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

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



Jura wrote:

<Then there is the work of Zhou and Niswander (1996), and Sawyer & Knapp (2003) 
that show an antagonistic relationship between scales and feathers, with the 
scales on birds legs being a re-acquisition of the trait (by actively 
suppressing feather development) rather than being a hold over. This has 
further been supported by the discoveries of _Microraptor_, _Anchiornis_, 
_Pedopenna_ and a reassessment of the legs of _Archaeopteryx_ and 
_Confusciornis_ all of which showed feathers extending down to the feet, and 
suggesting that a "feathers all over" situation was the plesiomorphic 
condition. That birds have scales on their tarsal metatarsal region fits well 
with work by Alibardi & Thompson, showing that the scale formation on the this 
region of the foot occurs in a separate wave from that which covers the body.>

  While the antagonistic relationship between feathers and scales in birds may 
be apparent in a localized sense, there is no data in those works that supports 
a body-wide all or nothing hypothesis. This is especially true in birds where 
the two types of integument exist side-by-side on a single animal. When you 
raise the examples where feathers are present in various fossil maniraptorans, 
you ignore the presence of contradicting evidence that has been raised in the 
past on this exact topic:

  1. NGMC 91 (referred to the microraptoran *Sinornithosaurus*), like birds, 
preserved squamation on the pes, as well as various types of feathery or 
filamentous integument around the body.

  2. Squamation, as was pointed out before, does not always preserve in 
Liaoning fossils even when it is expected (e.g., in the Yixian choristodere 
*Hyphalosaurus lingyuanensis*). Thus the absence of squamation in some 
feathered fossils does not specifically point out an absence (even in the 
region where feathers are present) are not likely to be there. What do you 
think was present in the regions of various maniraptoran theropod limbs where 
filamentous or pennaceous feathers were absent, such as on the lower pes of 
*Archaeopteryx lithographica*?

  3. Descriptive anatomy of the filamentous or "quill"-like structures in some 
dinosaurs in which squamation is present (see Lingham-Soliar on 
*Psittacosaurus*) show that this material is intersperses and omnipresent, 
regardless of the position of the structures. Naysaying that the structures are 
"possibly also plants" is a hand-wave: You must somehow account for the 
potential that they are what they are claimed to be in your hypothesis to test 
said hypothesis. This works when we have isolated elements as in *Longisquama 
insignis,* where there is only one skeleton associated with the structures, and 
several specimens of structures but no skeletons. No other associative 
hypothesis has been forwarded to account for Jiufotang "quills" that are not 
integumental (yet), nor to account for their apparent hollow form, which is 
backed up by similar structures (in the same skeletal region) in *Tianyulong 
confuciusi*.

  4. While it seems that the hypothesis of competitive expression between 
scales and feathers in the legs of some birds it applicable, it appears this is 
not substantive to account for the material which shows filamentous versus 
squamous integument in OTHER parts of the body, such as the face, or the tail 
(see, for example, *Scansoriopteryx heilmanni*/*Epidendrosaurus 
ningchengensis*, where a patch of scales is preserved as a mould in the tail, 
while the limbs and anterior chest present traces of filamentous integument).

  5. Even more interesting, like some maniraptorans, *Tianyulong confuciusi* 
possesses multiple kinds of filamentous integument, including flattened fibers, 
small hollow tubes, and basally bound, branching bundles [hah!] of filaments 
(as is found in NGMC 91).

Cheers,

Jaime A. Headden
The Bite Stuff (site v2)
http://qilong.wordpress.com/

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)

"Ever since man first left his cave and met a stranger with a different 
language and a new way of looking at things, the human race has had a dream: to 
kill him, so we don't have to learn his language or his new way of looking at 
things." --- Zapp Brannigan (Beast With a Billion Backs)
                                          
_________________________________________________________________
Hotmail has tools for the New Busy. Search, chat and e-mail from your inbox.
http://www.windowslive.com/campaign/thenewbusy?ocid=PID28326::T:WLMTAGL:ON:WL:en-US:WM_HMP:042010_1