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Re: More about Erickson et al. 2004 and RE: Delayed "growth spurt" in T. rex



I still haven't had a chance to see the paper, but I've got a question.
Did the authors compare the _T. rex_ growth curve with the growth curve
of the salt water croc or the Nile croc?

Considering that these are the only extant large archosaurian predators,
and considering that we have good ecological data on these animals, it
would have been the logical comparison to make.  And this is a case where
a negative correlation with crocs would be just as informative as a
positive correlation!

<pb>
--

On Thu, 12 Aug 2004 11:52:33 -0500 "Jonathan R. Wagner"
<jonathan.r.wagner@mail.utexas.edu> writes:
> To throw in my two cents: the "twisted"  (grab the middle of the 
> curve and 
> turn counter-clockwise) growth curves of tyrannosaurs make sense 
> both for a 
> small-pack scenario and tyrannosaurs as loners.
> 
> In the former case, it might be advantageous for a family-group pack 
> 
> (pride?) to maintain a small stock of smaller juveniles, either to 
> assist 
> in hunting (if that is what they did), or simply to ensure that a 
> few of 
> them survived "training." With one or more large adults already 
> present, 
> smaller juveniles means less food expended on them, which means 
> fewer kills 
> are necessary (less danger, good thing). The need for more food that 
> 
> probably coincided with the steeper portion of the growth trajectory 
> might 
> then have coincided with an increased appetite (as it seems to in 
> humans 
> :), monopolization of pack resources by the teenager, and might have 
> 
> triggered expulsion from the pack. This, of course, NEVER happens in 
> human 
> families... ;)
> 
> However, as others have noted, sigmoidal growth curves are the rule, 
> rather 
> than the exception. Rapid growth may simply have been a way to 
> rapidly 
> traverse the size gap between the "small" predator niche (1 ton... 
> recall 
> the gap between small and large predators in Late K northern Great 
> Plains 
> faunas), and that of the largest predators. If tyrannosaurs were 
> territorial, particularly abundant, or simply hungry, they might 
> preferrentially eliminate the competition while it is younger and 
> smaller, 
> but just beginning to compete for the same resources (large 
> herbivores), 
> rather than wait until it hits full size. It is possible that such 
> rapid 
> growth to great height necessitates a long lead time; that makes 
> sense 
> graphically, but I'm not sure what the biological reason would be.
> 
> As for why there aren't any really old tyrannosaurs, I very much 
> liked the 
> point about r-strategy in tyrannosaurs. We should remember that 
> these 
> animals are not large mammalian HERBIVORES, they are top predators. 
> That is 
> a very rough life, with angry prey, other large predators, disease, 
> 
> tripping and killing yourself, etc. If there truly wasn't much 
> selection 
> for long life, there certainly would have been a large number of 
> potential 
> means to shorten it!
> 
> Not that this is anything new, I just felt the need to pipe up. 
> After all, 
> this IS the Theropod Mailing List!
> 
> :)
> 
> Wagner
> 
> P.S. Don't forget to cc me in replies!
> 
> 
> 
> 



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