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re: Ptero ilium size



Chris Bennet wrote:

Unless David knows about some pterosaur mummies that I am unaware of, I
would reject his suggestion that "longer ilia means [sic] larger thigh
muscles."  We do not have any direct evidence as to the mass of the
musculature of the muscles, as has been often pointed out be people
reconstructing musculature based on bony processes and muscles scars and
those rejecting those reconstructions.  


>>>>> While the soft wet muscles may be long gone, the somewhat harder, 
>>>>> somewhat drier skin leaves impressions in a few pterosaurs, especially 
>>>>> since this is the area of fuselage fillet insertion. In Jeholopterus and 
>>>>> Dendrorhynchoides, for instance, the fuselage fillet terminates on a 
>>>>> straight line drawn between the knee and anterior ilium. Other 
>>>>> pterosaurs, where this portion is preserved, are similar. In some 
>>>>> Pterodactylus the dessication has brought the fillet to the bone itself, 
>>>>> something that I'm sure most people can understand was not the condition 
>>>>> in life.

CB wrote :
The elongation of the ilium is best
interpreted as changing the mechanical advantage of the muscles originating
from it, moving the origin further away from the center of joint motion (in
this case the acetabulum).  Immense muscles could originate from a small
area by way of a tendon 


>>>>>  This is true to some extent in lizards and alligators. Is it not?


CB wrote:
and small muscles can have broad areas of origin.

>>>>  Can't think of any muscles on any taxa like this. Example?

CB wrote:

The elongate ilia of most if not all pterodactyloids are expanded somewhat
presumbaly [sic] to provide more area for the origin of muscles, 


>>>>> and thank you for thatâ?¦

CB wrote:
but the ilia of
basalmost pterosaurs are relatively narrow straight rods that simply suggest
changes in the mechanical advantage of muscles relative to their ancestors
with shorter ilia.


>>>>> You would have to go back to the ancestors of the ancestors of the 
>>>>> pterosaurs to find shorter ilia. Back to Langobardisaurus. And the ilia 
>>>>> of basalmost pterosaurs (MPUM 6009) are slender, but elongated (more than 
>>>>> a third of the torso from ant. to post.), as in Sharovipteryx, known for  
>>>>> over 30 years. 

All in all it sounds like we're arguing not over length or width, but over the 
third dimension, depth. And like Homer Simpson in 3D Land, suddenly I'm out of 
my element   :  )  because all my best evidence comes from roadkill.

David Peters
St. Louis


Chris