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Delayed "growth spurt" in T. rex



Anyone care to speculate on why the "growth spurt" phase in the _T. rex_
young occured 10 years AFTER the animal's birth?  Logically, such a
growth spurt would have taken place from birth through adolescence.

Are there any modern analogs to this developmental style?

<pb>
--


On Wed, 11 Aug 2004 14:37:41 -0400 "Thomas R. Holtz, Jr."
<tholtz@geol.umd.edu> writes:

> Where are the old tyrants?:

> The reason may be related to something that Carrano & Janis, Paul, 
> and
> others have noted before: that non-avian dinosaurs were more r- 
> than
> K-selectors in terms of ecology.  That is, their much higher rate 
> of
> replacement (a dozen or more eggs per clutch, as opposed to a 
> single
> offspring in 2 or more years for elephant-to-indricothere sized 
> placentals)
> would mean that tyrant populations could be maintained without 
> having to
> have long-lived adults. (And the same is true for all large bodied
> dinosaurs). In contrast, large-bodied mammals would need to live for 
> longer
> durations in order to ensure a sufficient number of young in a 
> population.
> So natural selection can favor long-lived placentals where the same 
> type of
> selection would be weaker on big dinos. Large dinosaurs appeared to 
> have
> grown fast like mammals, but don't appear to have their long 
> lifespans.


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