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

[DinoBoyGraphics@aol.com]

>>>I would also like to say that unless there was a special novel muscular 
>>>anatomy of the legs not seen in any bird, croc, lizard, or other tetrapod 
>>>known today that would have been able to control such feather-moving 
>>>structures, this is one of the more unparsimonious arguments to assume that 
>>>these animals were particularly terrestrial _and_ capable of maintaining 
>>>leg-feather security.<<<

Um, no.  The hindleg feathers are themselves totally novel from
any "bird, croc, lizard, or other tetrapod known today," so no matter what the 
attachement or musculature you assume (moveable or not) you are making a 
third-level EPB inference.  And even if they were totally arboreal, the 
feathers would still get destroyed if they could not fold back when not in use. 
 Because the feathers had to be tucked back regardless of arboreal/terrestrial 
status, their presence makes not an iota of difference in the debate, unless 
one assumes a priori their function.  So what did they do?  Mor on that later...

>>>Avian femoral orientation laterally from the belly has been explained not as 
>>>a climbing adaptation, or even particularly
arboreal, but as an accomodation of the visera beneath the pelvis and the 
requisite widening of the thorax and pelvis ... the femora had to orient 
laterally to accomodate.<<<

The typical theropod everted femur, which becomes more everted as it is 
protracted and less so as it is retracted, in no way allows lateral splay.  In 
dromaeosaurs it simply everts a bit more as it is protracted;  Unless 
Microraptor has a pelvis and/or femur totally different from that of say, 
Bambiraptor and Deinonychus, there is no way for it to employ the hind-limb 
remigies as a "butt-fan," or as to generate lift furing gliding.

>>the feathers also show the same increasing distal symmetry of their brachial 
>>remiges, implying a direct aerodynamic connection...<<<

I totally agree, but:

>>>...and likely for some form of flight advantage, whether they were flapping 
>>>or not.<<<

Well maybe, depending on how you mean that.  I apologize if I am misreading you 
here, but it sounds like you are making Feduccia's classic mistake of 
associating aerodynamic function with lift generation in flight.  With the 
limbs tucked up during a glide-leap or powered flight (not taking a position 
here at the moment) the limbs become stabilizers/rudders, they could not 
generate lift.  The aerodynamic shape would reduce drag from the rudders, and 
make them more effective.  Unless someone can demonstrate a unique morphology 
that would allow the rear remiges to be used in a manner sub-horizontal 
relative to the line of the body, they cannot be butt-fans and/or passive lift 
generators.

    Note that I am not saying that Microraptor wasn't gliding or even flying, 
it likely was.  And it may have gotten up in trees to take advantage of 
gravity.  But if it did so, the lack of specializations to an arboreal 
lifestyle suggests it was a secondary spread to the trees allowed by their 
partial mastery of the air, not the remnents of a lineage of arboreal scansors 
that birds evolved from.

     Everyone please stop drawing spread-eagle sinornithosaurs until there is 
convincing osteological evidence for a unique hind-limb locomotor use.

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

(307) 742-3799