Re: Tyrannosaur age-population distributions

[Phillip Bigelow <bigelowp@juno.com>]

On Sun, 16 Jul 2006 13:32:55 -0400 Graydon <oak@uniserve.com> writes:
> On Sun, Jul 16, 2006 at 09:27:41AM +0000, Phillip Bigelow scripsit:
> > On Sun, 16 Jul 2006 08:46:02 -0400 Graydon <oak@uniserve.com> 
> writes:

> > > Were tyrannosaurine packs accreted on a basis of purely social
> > > bonds?

> > Heh.  Keep in mind the size of a tyrannosaurid's brain.  *IF* pack
> > activities occured, was it instinctual?  Yes.  Instinct usually 
> drives
> > behavior in non-mammalian vertebrates.  But was it "social" 
> behavior,
> > sensu lion prides?  Who knows, but I doubt it.

> I don't doubt it at all; chickens have social behaviour,
> and 
> chickens
> aren't any smarter than a tyrannosaurid and arguably less.


If you look at the E.Q. (encephalization quotient) for tyrannosaurids and
the E.Q. for chickens (and the E.Q.s for *all* living birds, in fact),
you will find that _T. rex_ adults lag behind all extant birds in the
Brainiac Department.

Robert Carroll's (1988) _Vertebrate Paleontology and Evolution_ textbook
has a graph showing the E.Q.s of the various relevent taxa.

Then there is the quantum jump between the E.Q. of extant birds and the
E.Q. of carnivorous mammals (like pack-forming animals.  Lions, for
example).

_T. rex_ is "brainier" than crocs (and most herbivorous dinosaurs), but
that isn't saying much.  Most of _T. rex_'s brain volume was taken up by
the animal's sensory subsystems (olfactory lobes, and to a lesser extent,
its optic lobes).  But for complex social interactions, a larger cortex
is needed and _T. rex_ just doesn't measure up in that Department.

<pb>
--
Why do chicken coops only have two doors?
Because if they had four doors, they would be chicken sedans.
(as told to me by my neighbor's son)