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Re: Vestigial Arms (was: Theropod limbs - how mobile?)




On Sunday, May 19, 2002, at 11:18 PM, David Marjanovic wrote:

Here is how I picture tyrannosaurids using their arms for intraspecific
combat. The claws are pointed inward, and very little (if any) forearm
rotation is necessary.

http://homepage.mac.com/john_conway/tyrannosaurus-armwrestle.jpg

But it requires a lot more rotation in the shoulder joint than was possible
according to the paper.

I wish I had this paper, I am at a disadvantage. Anyway, all you have to do is move the two rex's closer together, and the shoulder hasn't got to swing out so far (not that I think they really are, see below).


At least the left wrist of the left one is flexed
too far,

I's a SKETCH, not a definitive diagram. What do you want for twenty minutes work?


and what are the big, pointed claws good for?

?.... the casts I have handled have big, pointed claws. Even if this isn't right, it doesn't make much difference to the point we are arguing.


-- And were they
capable of standing so upright?

The drawing is from underneath, to give a better view of the arms (not all drawings are from a horizontal viewing angle!). If you look at it how it is intended, the shoulders are not swung out very far, it has more to do with the angle you are viewing from.


BTW, from guessing the size of the coracoids
in your drawing, it looks like you made the entire arms as thick as the
bones are :-)

Again, it is just a sketch. If anything, the arms and coracoids are too big (not that the coracoids are very visible). The arms are about half the width of the coracoid in the drawing, which is about right as far as I can tell from the references I have on hand. But, yet again, it is just a sketch.


Look, all I really wanted to do is illustrate a point, so you would know what meant. I think that idea is plausible, and I have the picture to prove it. :-)


John Conway, Palaeoartist

"All art is quite useless." - Oscar Wilde

Protosite: http://homepage.mac.com/john_conway/
Systematic ramblings: http://homepage.mac.com/john_conway/phylogenetic/