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Moving out of my bird and reptile phylogeny niche is weird, but here goes...

<<The key to understanding rearing, in my humble opinion, is
understanding what is going on at the hips and the tail.  Can the hips
rotate back far enough to allow the sauropod to go tripodal?  Could
the tail support the sauropod tripodally?  Could a sauropod stand on
just its hind legs?  What of the caudofemoralis longus muscle which
runs off the tail and inserts on the middle of the back of the femur
on a landmark called the fourth trochanter?>>

These are all interesting questions in relation to discussion of sauropod rearing that I think need to be asked. However, would some sort of phylogenetic bracketing be useful as well? Although I am doing little else other than playing Devil's advocate here, all the models in the world may not allow you to find out how something could actually move in real life. (See below.)

<<I am planning on addressing sauropod rearing to a point in my
dissertation, and I am busy at work on a physical model (and hopefully
later a computer model) of the sauropod forelimb and hindlimb/tail.
The forelimb model is complete, but the hindlimb/tail one needs some
work yet.  My hypothesis going into this is that the rearing in
sauropods is going to be limited by that C. longus muscle and how far
the pelvis can rotate back as the animal reared up.>>

Cool. Exactly what are the limitations of the M. caudofemoralis longus? Are we talking about relative size and attachment? In many types of birds the M. caudofemoralis longus is reduced to a simple ribbon of tissue, and too my knowledge they have little problem lifting and pivoting at their hips even with the center of gravity located in the breast (mass depends on the bird, but it goes as high as 60-70% if I remember my George and Berger). This is where the bracketing thing comes in: would comparisons (though admittedly they are very tenous and different in this situation) with modern birds and crocs be useful for at least giving an idea as to how the muscle would accomplish this?

Matt Troutman

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