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RE: New Tyrannosaurus paper



Tracy:

Hutchison has gone into the differences in locomotion between birds and
more basal theropods in huge detail in previous papers.  A few are cited
below.  I don't pretend to understand all of it, but its fairly safe to
assume that this is not a mistake he'd make.  

>From the newspaper accounts, it also doesn't look like the detailed
mechanics have much to do with the result here. Its just a matter of the
energetics of moving a body of that size over the ground.  How the
pieces fit together won't have much effect on the muscle mass needed to
do the job.

That said, you may have a point about the ilia.  If (big if) I remember
Hutchison's papers well enough, that would mean a big caudofemoralis.
Having much of the muscle mass for the legs actually reside along the
hip and base of the tail might allow the dinosaur to cheat a bit on any
assumption that the leg muscles must be in the leg.

The cnemial crest may be more problematic.  I dunno exactly what the
crest was used for in non-avian dinosaurs, but one might suspect that it
is related to an ability to swing the lower leg through a wide arc
*without* moving the femur so much. That's the way it gets used in, for
example, loons.  Now a real bipedal sprinter might not need that
mechanism. Its got time in the air to move the tibia, and it's pumping
the femur up and down for all it's worth in order to get speed at the
expense of efficiency.  The more likely conclusion might be that the
tyrannosaur was either adapted for long-distance efficiency or to make
the most of stride length in a fast walk. 

But, as you say, lets read the paper and find out.  

For what its worth.

Hutchinson, JR (2001), The evolution of pelvic osteology and soft
tissues on the line to extant birds (Neornithes). Zool. J. Linn. Soc.
131: 123-168. 

Hutchinson, JR (2001a), The evolution of femoral osteology and soft
tissues on the line to extant birds (Neornithes). Zool. J. Linn. Soc.
131: 169-197.

Hutchinson, JR & SM Gatesy (2000), Adductors, abductors, and the
evolution of archosaur locomotion. Paleobiology 26: 734-751.

  --Toby White
HG
The Vertebrate Notes at
http://home.houston.rr.com/vnotes/index.html
and http://www.dinodata.net

[moving soon!]


> -----Original Message-----
> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu] 
> On Behalf Of Tracy L. Ford
> Sent: Wednesday, February 27, 2002 9:16 PM
> To: Dinonet (E-mail)
> Subject: RE: New Tyrannosaurus paper
> 
> 
> 
> 
> -----Original Message-----
> From: owner-dinosaur@usc.edu 
> [mailto:owner-dinosaur@usc.edu]On Behalf Of > Jeff Hecht
> Sent: 
> Wednesday, February 27, 2002 1:06 PM
> To: TiJaWi@agron.iastate.edu; 'dinosaur@usc.edu'
> Subject: Re: New Tyrannosaurus paper
> 
> I wonder about this, and if they really looked at the skeletons?
> 
> Fact, Tyrannosaurs rex's ilia are tightly oppressed, almost 
> to a point where the sacral neural spines are crushed, more 
> than any other theropod; meaning large muscles. 
> Giganotosaurus doesn't have this. The cnemial crest on the 
> tibia is HUGE. If the animal didn't move fast why have such a 
> huge cnemial crest?
> 
>  A chicken is not a T. rex. A chicken's body is totally 
> different. The femur articulation is totally different. The 
> femoral head is nearly at a right angle to the tibia in a 
> chicken while in a theropods is nearly vertical, I've said 
> this before and should be some where in the archives. Birds 
> and dinosaurs walk differently, and differently with their 
> muscles. Did the authors just ASSUME birds and theropods 
> walked the same? You can't assume they did because the 
> skeletal structure is different. Greg Paul and Per Christian 
> have an article in the theropod Gaia volume on the leg 
> movement in Tyrannosaurus. Was this article mentioned?
> 
> I'll have to wait till next week when I get the article. I 
> doubt the paper is all that accurate in depicting the 
> behavior of Tyrannosaurus rex.
> 
> Tracy L. Ford
> P. O. Box 1171
> Poway Ca  92074
> 
>