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MONONYKUS' ARMS



Fellow dino-listers,

I think I am going to have to agree with most posters on this list (the vocal
ones at least) in my opposition to the idea that _Mononykus_ used its
forelimbs for digging.  In looking through:

Perle A, Chiappe, L M, Barsbold R, Clark, J M, and Norell, MA.  1994.
 Skeletal Morphology of _Mononykus olecranus_ (Theropoda: Avialae) from the
Late Cretaceous of Mongolia.  American Museum Novitates.  Number 3105, 29 pp.

I came upon the diagrams of some of the animal's eliments and have gotten
some tentative estimates of the length of said elements:

Total length:     ~100 centemetres
Scapula + Corocoid:     ~7 centemetres
Forelimb:     10 centemetres
  Humerus:     4 centemetres
  Radius:     ~2 centemetres
  Hand + Fingers:     ~4 centemetres
Neck + Head:     25 centemetres
Hindlimb:     48 centemetres
  Femur:     14 centemetres
  Tibiotarsus:     ~17 centemetres
  Foot + Toes:     ~17 centemetres

What we are seeing with these measurements is that a fairly large animal,
bigger than most digging animals that I know of, was digging holes perhaps 10
centemetres (4 inches) deep with a big neck and body blocking any deeper
holes.  Doing this of course while squatting on its belly with its big half
metre hindlimbs going somewhere to get out of the way of its forelimbs.  This
thing was not digging burrows.

And digging for what?  The semi-desert that it lived in didn't, as far as I
know, have much in the way of fossilised subsurface insects etc.  Perhaps it
was digging for roots or tubers. These scenarios I find unlikely too because
the ultra-short forelimbs cause such a silly pose.  If it was really digging
in the ground, one would expect longer forelimbs, or a body that wasn't so
lanky.

One suggestion that isn't quite so silly, is the idea that perhaps they used
their claws to strip bark for beetles or other sorts of under-bark insects or
whatnot.  This is also not very likely to me (though more likely than the
first idea) because the claws are not very coordinated as one would expect to
dig out insects in bark.  _Mononykus_ is also a little large to be eating
just insects anyway.

For me, I believe that the arms were nothing more than sexual display
devices, and also perhaps they were implimented in intra-specific combat,
which could explain the great muscle attachments surrounding them.

There's my two cents, flame away...

Peter Buchholz
Tetanurae@aol.com

"Kissing . . . is a goodness," he explained.  "It beats the hell out of card
games."