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Re: Tyrannosaurus tail torque (also thinking about adaptations in juveniles vs. imagos)



On Fri, 19 Nov 2010 00:09:28 -0300
Augusto Haro <augustoharo@gmail.com> wrote:

> 2010/11/18 Jonas Weselake-George <ee555@ncf.ca>:
> 
> > It may be valuable to think of additional factors beyond top speed.
> >
> > Some of the muscle mass may be optimised for endurance - with such
> > long legs exhausting prey through "out walking" them may have been
> > extremely effective.
> >
> Great idea, something similar to the canid approach. As far as I know,
> canids are not faster than many of their prey item but can reach them
> because of exhaustion. 

Thanks. The comparison is exactly what I had in mind.

I would add to your interesting points on air sacs two features: The
generally greater efficiency of bipedal locomotion over quadrupedal
locomotion and the longer legs - both of which would have given
all known tyrannosaurids a significant advantage over equal mass prey.

Of course, this is in the straight and level: A lot of prey may have
had advantages on certain types of terrain and most species would have
been more manoeuvrable.

> Tyrannosaurus also had titanosaurs and ankylosaurs to prey upon if
> velocity or stamina was not their thing. May their greater estimated
> bite force and banana teeth have something to do with specialization
> into killing ankylosaurs? Ankylosaurids may kill or severely disable
> with their blows, but bovids and suids can also kill -and sometimes
> do- or severely disable with their horns and tusks, yet lions and
> other predators still largely hunt them. Can we scientifically answer
> how much efficient were ankylosaurid defenses against theropods in
> comparison with the horns of bovids?

One major difference between canids and tyrannosaurids is that
tyrannosaurids would generate more lethal bite forces and thus could
execute cornered or exhausted prey more easily. 

If one examines the difference between the suffocating kills of large
cats and the long and dangerous way wolves gradually injure their prey,
one gets a sense of how much more optimised predators can be (although
experienced wolves can ambush and bring down moose with a single bite).

So the hunting strategies could be quite different - even if both use
endurance.

On another note:
The picture is also incomplete if we don't think about juvenile and
sub-adult tyrannosaurids. In any ecosystem the young would be
considerably more than three-quarters of the population and may have
filled a completely separate niche. The changes are great enough that
it might even be appropriate to refer to the adults as the "imagos" of
the species (especially given the short life expectancy upon reaching
maturity).

It would be interesting to try and estimate whether adult or sub-adult
tyrannosaurs consumed more prey in a typical ecosystem.

It might also be possible to infer something of the speed requirements
for different types of prey through apparent niche partitioning between
the smaller and faster juveniles and the larger, stronger adults.

However, this may be deceptive - as speed in sub-adults may be a
compensatory adaptation for having a high centre of gravity - itself
an adaptation to endurance.

A lot of speculation - but there is certainly more to life than speed,

-Jonas Weselake-George