Re: Feathered Dragons: Studies on the Transition from Dinosaurs to Birds

[DinoBoyGraphics@aol.com]

I apologize to Jaimie and the few who are still reading this thread that I 
haven't responded sooner:

>>>The feathers themselves exist in birds today. It would not be much of a 
>>>stretch of the imagination to assume that birds back to the beginning had 
>>>them, and in fact this is supported in the fossil record, all the way to 
>>>their toes. The novelty here is the manipulating musculature, which doesn't 
>>>exist in any tetrapod I know of, at least.<<<

    Rather obviously feathers, including those on the hindlimbs, exist in 
birds.  It is the asymmetrical aerodynamic feathers on the hind legs of 
Microraptor (and others) that are unique.    No extant feather-based 
aerodynamic structure today lacks muscular control, and it is hard to see how 
the feathers could have done much more than induced drag without the ability to 
manipulate them, even if you assume a spread-eagle dromaeosaur.  Furthermore, 
if they could not fold up, the hind-"wing" feathers would get just as damaged 
moving amongst foliage.  So the presence of these unique structures do not 
support a priori the idea of arboreality.

>>> I recall making this point all last year prior to the publication of Paul's 
>>> article in _Prehistoric Times_ wherein he advocated hindlimb wings as 
>>> archetypal as those of the forelimbs.<<<

Perhaps you should have stuck with it? ;)  I have the utmost respect for GP's 
work, but I did not find the PT article (or his poster at SVP) convincing as to 
lateral splay in sinornithosaurs.  I have looked at some of the material 
myself, and have very high resolution images of "Dave," and I think he has 
mistaken damaged femoral heads for morphological changes.  He may be right and 
I may be wrong; more specimens will hopefully clear up the issue once and for 
all, but in the meantime (and based on the data I have) I am very skeptical of 
spread-eagle Sinornithosaurs.  It is interesting to note that if Archaeopteryx 
did have have hindlimb "wing" feathers, they were of use to it despite its 
normal theropod-style erect limbs.

>>>Actually, I had in mind the idea that a foil or horizontal wing in aiding 
>>>speed and decreasing lift properties, as in Hartman's own presentation at 
>>>SVP a few years ago on *Caudipteryx* using wings and tail as a terrestrial, 
>>>cursorial adaptation.<<<

     How dare you use my own words against me!  In all seriousness, I'd 
appreciate it if you could send me a more detailed description or illustration 
of what you are describing, because it is hard for me to envision.  But I think 
I see were we are miscommunicating.  I am not claiming that the vertical 
hindlimb "wings" are adaptations for cursorial existence, only that they are 
not inconsistent with it.  I suspect they were used as stabilizers during short 
ballistic leaps (or perhaps not so short, depending on how much thrust the 
forelimbs could produce as this stage).  As for your assertion that rudders 
should not be hemispherical, enter "airplane tails" into google's image search 
and check out the second airplane (the yellow and blue one).  Many older plane 
tails had a sharp vertical leading edge and a rounded hemispherical trailing 
edge (including spitfires, which you can also put into Google).  It may not be 
perfectly efficient, but neither is evolution, and feathers are!
  n!
ot exactly good for making angular control surfaces.  If it worked in planes it 
probably would be good enough for dromaeosaurs.

    This is where I think the the repeated fallacy by many (but perhaps not 
Jaime) comes in.  We are so hooked on the idea of aerodynamic surfaces for 
gliding or powered flight we forget about control and other uses that 
aerodynamic surfaces have.

>>>...this argument was handled largely by Cunningham who offered that they 
>>>could, in fact, have a positive effect on lift.<<<

To quote from Jim: "Assuming appropriate articulations and load bearing 
structures, it could work as a glider.  Without doing numbers, I'm not sure how 
well.  One wouldn't want to just guess at it."

    But without persuasive evidence that sinornithosaurs have limbs different 
from all other dinosaurs, "guessing at it" is exactly what one as to do.  He 
further states: "Until one determines the articulations and attachments, I 
don't see how
any conclusions can be drawn, only speculations."

     No one has has demonstrated the lateral-splay ability of sinornithosaurs, 
and I am not the only one who thinks so.  Yet for some reason the 
gliding-through-the-trees scenario seems to
be quickly approaching cannonization.

>>> What features does *Microraptor* lack that prevent it from being particular 
>>> arboreal or scansorial? Aside of course from the unnecessarily sprawled 
>>> femur.<<<

     Remember, I am not saying that microraptor could not climb trees.  Rather 
than terrestrial ballistic leaps it may be that it often climbed trees to use 
gravity to accelerate after prey.  But it does not have other adaptations seen 
in arboreal animals.  It does not have longer distal pes phalanges than 
proximal ones.  It has a high center of gravity (bad for horizontal leaps in 
trees).  It has a long manus (non-brachiating arborealists usually have short 
hands and feet, to avoid leverage problems when climbing).  It has a long stiff 
tail.  These do not "prove" it wasn't arboreal, but what features are 
consistent with arboreality?  These arguments, after all, must go with the 
preponderance of the evidence, not one or two "keystone" characters. 

Best wishes,


Scott Hartman
Zoology & Physiology
University of Wyoming
Laramie, WY 82070

(307) 742-3799