Re: Tyrannosaur age-population distributions

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

Quoting Phillip Bigelow <bigelowp@juno.com>:

> _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.

I think you'll find that this idea is outdated poppy-cock (if you'll  
excuse my French).

The sheer complexity of intra-species interactions such as that  
exemplified by the ecological niche of the cleaner wrass suggests that  
brain size is not a good indication of the presence or absence of  
complex social interactions. In this example, several species of fish  
have to temporarily modify their natural instincts in order to take  
advantage of the services provided by cleaner wrass. The wrass  
themselves also have to be able to interpret the signals given by  
other species in order to approach without fear.

Great White sharks engage in complex social interactions with one  
another, communicating their feelings via body posture. They've been  
shown to recognise familiar animals by sight, and exhibit signs of  
stress when a strange shark gets too close. They communicate their  
nervousness by slightly arching their backs and dropping their  
pectoral fins down, which warns a stranger not to get too close.

Complex social behaviour needn't necessarily be 'conscious' social  
behaviour, hence it doesn't always require a large cortex.

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Dann Pigdon
GIS / Archaeologist         http://heretichides.soffiles.com
Melbourne, Australia        http://www.geocities.com/dannsdinosaurs
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