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RE: Walking Rex Paper



 

 

-----Original Message-----
From: MariusRomanus@aol.com [mailto:MariusRomanus@aol.com]
Sent: Thursday, February 28, 2002 2:39 AM
To: dino.hunter@cox.net
Subject: Walking Rex Paper

 

This was sent to me and he forgot to send it to the list also.

 

Here's the paper. Put it this way, you've been right about everything you've said about it. The paper even starts right off with a bang: "Most assessments of running ability in large theropods are qualitative, based on analogies to walking elephants or running birds and hoofed mammals." Yes,... Oh so very true..... Too damn bad this study was no different.

This remark is just so precious..... "For extant animals, our results matched reality: alligators cannot run bipedally, whereas chickens are adept runners. Our dissected Alligator only had about 3.6% mbody per leg as extensor muscles, but we estimated that it would need about 7.7% mbody per leg to run quickly on its hind limbs." Is it just me? I mean, it could be just me, but.... those sentences are so pointless on so many, many levels, that I fail to see why they were even written for this paper. But, like I said, it could just be me.

There are statements that are made that fly in the face of all reason..... I mean, statements that are completely contrary to reality. Example: "Although our T estimates are somewhat high (10â21% mbody per leg), a more columnar limb orientation could easily have reduced T enough to enable fast running (5% mbody)."  So, the flexed knees of all the fast terrestrial animals, with their flexible ankles and all, is wrong. They should be the slow ones and elephants with their stiff, columnar legs, should be the fast ones??????? "If Tyrannosaurus was indeed an adept runner, then it must have had many musculoskeletal specializations that available data do not suggest."  Or, since the paper didn't take into account spring-loaded tendons, the completely different musculature setup, and that wonderful shock absorbing, joint lubricating stuff called cartilage, but only paid attention to hip height and muscle mass comparable to a croc's and a chicken's, the calculations and conclusions are just wrong. "We isometrically scaled-up our chicken model to 6,000 kg to simulate a Tyrannosaurus-sized chicken. Our model shows that a gigantic chicken, using the same limb orientation as an extant galliform........ Features such as the more posterior position of the trunk centre of mass of Tyrannosaurus explain why we obtained lower estimates of T for Tyrannosaurus (43% mbody per leg) than for the 6,000 kg chicken"..... Uh huh....... What about,... oh I don't know...... The completely different locomotary apparatus that tyrannosaurs have??? You think that could have been one of your other features??????? Like I said Tracy, you are completely right. Mike D. needs to insert his foot into his mouth.

"A walking tyrannosaur could have adopted more extended limb joints to lower the GRF moment arms (R) and used double limb support to reduce the GRF, decreasing the T required for walking within reasonable bounds. However, our calculations suggest that even a walking tyrannosaur required activation of a large fraction of its extensor muscle volume, at considerable metabolic expense." Okey Dokie then....... rearrange the anatomy and physiology so that the study can at least say that the animal could even walk.... Sure.... that's reasonable....

This sucker is a barrel of laughs. Given that I'm a no-body on this list, and have only just started posting on it, I'm leary about pissing off too many people as of right now. I've watched for years and have seen what happens to those that are black listed. Like I said with my last post dealing with the condyles of the humeri.... It's not wise for me to be screwing with the gods. :-)  If the situation was different, I would have posted this on the list for one and all to read and then beat me.

Kris

 

Some comments from me.

 

"For extant animals, our results matched reality: alligators cannot run bipedally, whereas chickens are adept runners. Our dissected Alligator only had about 3.6% mbody per leg as extensor muscles, but we estimated that it would need about 7.7% mbody per leg to run quickly on its hind limbs."<<

 

 

Ah DUUHH!! Of course alligators canât run bipedally!!! This is a bad analogy!

 

 

>>We isometrically scaled-up our chicken model to 6,000 kg to simulate a Tyrannosaurus-sized chicken. Our model shows that a gigantic chicken, using the same limb orientation as an extant galliform........ Features such as the more posterior position of the trunk centre of mass of Tyrannosaurus explain why we obtained lower estimates of T for Tyrannosaurus (43% mbody per leg) than for the 6,000 kg chicken"..<<

 

 

As has been pointed out before, chickens and theropods have different body and leg movements, this test is mote. I suppose for me to get listened to Iâll have to get a PhD.

 

 

 

Tracy L. Ford

P. O. Box 1171

Poway Ca 92074