Re: To Sprawl or Not to Sprawl?...

[DinoBoyGraphics@aol.com]

In a message dated 5/5/2004 3:19:41 PM Eastern Daylight Time, 
twilliams_alpha@hotmail.com writes:

>>> (1) The femoral morphology of _M. zhaoianus_ may not be the same as that of 
>>> and _M. gui_.  The former appears to have the normal theropod-type femoral 
>>> head (also retained in birds); but _M. gui_ may have a derived subspherical 
>>> femoral head allowing a "sprawling" hindlimb posture.  (If this is the 
>>> case, this would undoubtedly warrant generic separation for _M. gui_).<<<

     If this IS the case, it would most certainly warrant generic seperation.  
But without strong positive evidence, I don't see how this is anything but 
special pleading.  It took tens of millions of years to rearrange the forelimbs 
from the primative theropod condition (e.g. posterior facing glenoid) to a 
flapping configuration, but you think (nearly?) contemporal sister-taxa have 
totally different pelvic and femoral structures?  Remember that making the head 
spherical is only one small step.  You would have to close off the acetabulum, 
and you would have to totally change the insertation points on the proximal 
femur.  You are talking about truly radical shifts in the embryology of the 
animal.  

Since the feathers could have been useful without employing them horizontally 
(e.g. rudders), there is no evidence right now to support the sprawling M. gui 
idea.

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

(307) 742-3799