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

[John Conway <john_conway@mac.com>]

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/