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Re: standing t-rexs

Cliff Green said:

    "I have a question  that has to do with my dino art. Could a theropod
like T-Rex prop itself up on its haunches like a kangaroo, just like in the
old Charles R. Knight renderings? In my own meager anatomical studies, I
haven't seen a problem with this being able to happen. Any input would be
most appreciated."

I'm no theropod expert, but one of the reasons why T. rex cannot rear up into the position you suggest is that the femur would have to become disarticulated to do so. As far as I know, the acetabulum (hip socket) of T. rex, like other theropods, has a bump called an antitrochanter. There is also a notch (again, as far as I know) on the back of its femur, near the femoral head. The femur can only extend so far past vertical before the notch on the back of its head locks with the antitrochanter. This appears to prevent the femur from rotating far enough back that the upright position of many museum specimens would be rendered impossible.

In the 1980 book "A Cold Look at the Warm-Blooded Dinosaurs," the late Nick Hotton describes very well the fundamental difference between the mechanics of a mammalian femur and acetabulum and that of a theropod dinosaur. I suggest you read his chapter for more information.

And, yes, as G. Paul has explained in his PDW book, the hip and pelvic musculature may have also prevented theropods from assuming such a "regal" position because assuming it would also mean avulsing most of the hip and pelvic muscles!

Good question.  Any thoughts, oh theropod mechanically inclined ones?

Matt Bonnan

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