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Re: Theropod limbs - how mobile?

From: John Conway <john_conway@mac.com>
Date: Thu May 16, 2002  01:35:44  PM Australia/Sydney
To: gasperex@hotmail.com
Subject: Re: Theropod limbs - how mobile?

On Thursday, May 16, 2002, at 08:46 AM, Steven Coombs wrote:

True, its [T.rex} hands are pretty well useless, but I wouldn't say they were capable of doing nothing. After all if its arms are estimated to lift 300+ LBS. If it was helping to lift its upper body (not all the help from its arms) or to cling on a carcass or to even cling onto a female during mating, its hands had to be used for something.

300 LBS = ?150 Kgs. Impressive as that is in human terms, it is weak in T.rex terms. T.rex's would weigh between four and eight tonnes (depending on the estimate and the individual); when it moved or stood up we are looking at many tonnes of force, not kilograms (or LBS). I can't see T.rex's arms being used to hold a female during mating, they would be ripped off. As for gripping carcasses, why? Why would it want to hold a carcass to it's chest? Even if it did, it could only hold relatively small chunks, because again, it's prey were also multi-tonne animals.

Is it possible that the heavy musculature on tyrannosaurid arms was simply retained from ancestors, and didn't serve any function?

On Thursday, May 16, 2002, at 05:56 AM, Williams, Tim wrote:

For an obligately bipedal carnivore like _Deinonychus_ I'm open to
alternative suggestions for why it had strong forelimbs.

Perhaps because it was neoflightless?

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/