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Re: A good day for tyrannosaurs

I think that ecological competition of the kind seen in laboratory
populations, under certain controlled conditions, is often difficult
to see or predict in wild populations.
We consider that ecological competition necesarily leads to the
extinction of one of the competing species from the lab, but then we
have lions and spotted hyaenas eating more or less the same, in the
same place, even killing each other from time to time, and they seem
to coexist instead, at least along the time humans have lived and
recorded the presence of both.
Some factor (or factors) impedes in this case each species from
extinguishing the other, and thus we should not consider, or expect,
that what happens in laboratory is the same which happens in the wild.
Expecting nature to behave like the laboratory may be reductionistic,
and may lead us to wonder why so many different species of similarly
sized theropods, hadrosaurs or ceratopsians, with similarly shaped
teeth, were able to coexist.

2009/10/7 Erik Boehm <erikboehm07@yahoo.com>:
> --- On Tue, 10/6/09, Dann Pigdon <dannj@alphalink.com.au> wrote:
>> From: Dann Pigdon <dannj@alphalink.com.au>
>> Subject: Re: A good day for tyrannosaurs
>> To: dinosaur@usc.edu
>> Date: Tuesday, October 6, 2009, 3:58 PM
>> On Wed, Oct 7th, 2009 at 9:33 AM,
>> Augusto Haro <augustoharo@gmail.com>
>> wrote:
>> > 2009/10/6 Dann Pigdon <dannj@alphalink.com.au>:
>> > >
>> > > It makes you wonder, though, how the
>> smaller-bodied tyrannosaur species managed to
>> compete
>> > > against the juveniles of the larger forms (where
>> they were contemporaneous).
>> >
>> > I suppose the chicks of larger taxa would have it
>> worst in such a
>> > competition, unless they were helped by their parents
>> and then
>> > consumed what the parents hunted, and not the
>> tyrannosaurids of their
>> > same size.
>> Growth rates seem to indicate that a 15-year-old
>> Tyrannosaurus would have been about the same
>> size as an adult Alioramus. Of course the two lived at
>> different times and in different places, but if
>> Alioramus had roughly the same size and build as
>> Nanotyrannus (assuming Nano to be a distinct
>> species), then adult Nanos would have had to deal with
>> equivalent sized sub-adult Tyrannosaurus
>> with *fifteen years* of hunting experience.
> And how many years hunting experience would an adult Alioramus have?
> An Alioramus like tyrannosaur could probably get along with less food, as 
> that juvenile T rex will need to eat a lot to be able to grow as quickly as 
> they did into an adult.
> Or is it possible there is some sort of Bi-stability in T-rex development, if 
> they don't get enough food as a juvenile, their growth is stunted, and they 
> end up looking like "Nano Tyrannus" as an adult?
> Could Nano-tyrannus be a neotenic offshoot of T rex?
> Someone else here thought it would be harder on the juvenile T rex rather 
> than the small adult Tyrannosaurs (unless the juveniles were accompanied by 
> large T rexs in family groups), as the small adults could begin reproducing 
> much sooner, and had lower food requirements.
> This could be offset in the T rex juvy, by concentrating on getting bigger 
> while the small adults concentrated on procreating.
> The juvy T rex would spend only a year or two at a size comparable to an 
> Alioramus, and after that could probably bully other dinosaurs away from 
> kills, and hunt larger prey, and I'd guess once a T rex reached adult hood, 
> it would live a relatively long time, at the very least it would have no 
> predators to worry about.
> Delay reproduction, but ultimately have a longer reproductive period?