Re: DINOSAUR digest 695

["Matthew Troutman" <m_troutman@hotmail.com>]

<<I appreciate Mathews clear citation of my work with Ken Dial and Kevin 
Middleton- a good lesson to us all on this list.>>

Thanks.

<<First, Ken and I did not "produce a cladogram based on their 
observations".>>

I should have worded it better.  I made it sound the way that it really 
wasn't, sorry.

<<Second, as we discuss in the Evolution paper and elsewhere, the tail 
of dromaeosaurs was more functionally decoupled from the hind limb than 
in basal theropods, but not as liberated as in birds.  Designating the 
tail as an independent module is a judgement call, but one we would 
defer until it took on aerodynamic function.  Obviously, there is a gray 
area when discussing concepts such as modules, but a functionally 
independent tail in a terrestrial animal is more difficult to 
identify.>>

Actually I was referring to the dromaeosaurid forelimbs.  There is 
evidence that the forelimbs had a birdlike myology.  The posterior 
rotation of the coracoid and other features suggest that bracing was 
being provided in the pectoral girdle.  Similiar arrangements are seen 
in birds and pterosaurs, animals that have strong pectoral muscles and 
need to brace the regions around them so they do not do any 
muscloskeletal damage.  The similiarity of the bracing and of the 
sternum and furcula in dromaeosaurs to birds suggests that they had a 
birdlike arrangement in their pectoral muscles.  This is supported by 
the work of Padian and Gautheir where they showed that the motions of 
the forelimbs were similiar to flapping in birds.  I am not suggesting 
that dromaeosaurs could fly, what I am suggesting is that perhaps 
dromaeosaurs (or perhaps their ancestors) used their forelimbs for 
locomotion possibly in the trees.  If this point can be proven then I 
believe that the dromaeosaur forelimbs could be classified as a 
locomotor module.  

Matt Troutman


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