Re: A good day for tyrannosaurs

[Dann Pigdon <dannj@alphalink.com.au>]

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.

Of course if Nanos *where* juvenile Tyrannosaurus, then there'd be no 
intraspecific competition 
(obviously).

Modern big cats in Africa (as an example) tend to have distinct physical 
differences. Leopards 
survive living around lions by climbing out of harms way, while cheetahs can 
easily out-sprint a lion 
if need be (using both greater speed and agility).

However most tyrannosaurs tend to have had a similar basic body form, and all 
appear to have 
been cursorial (no tyrannosaur 'leopard' analogues with those forelimbs!). I 
suppose that leaves 
the possibility of the smaller-bodied adult forms being like cheetahs - however 
Tyrannosaurus 
appears to have had extremely gracile hind limb proportions (at least compared 
to other large 
theropod groups), which I would think would make the lighter juveniles very 
quick on their feet.

-- 
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Dann Pigdon
GIS / Archaeologist                Australian Dinosaurs
Melbourne, Australia               http://home.alphalink.com.au/~dannj
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