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Re: re:dinosaur eyeballs



>(it was me)
>    Are there any birds with slit pupils?   Are there any birds that show the
>whites of the eyes?   Do crocodiles have round pupils or slits (and if slits,
>which way do they slit?).  Do crocodiles and other large modern reptiles show
>whites of the eyes?

Crocodilians (crocodiles and alligators) do have a vertical slit and the
white is never seen, as far as I am aware.

>    Are we looking at the high probability that dinosaurs had round eyes that
>showed no whites?  It would seem that in 145 million years, some variations
>in eye shape might have come up:  it hasn't taken mammals more than 70
>million years to come up with the variety they have, (and conversely, why
>don't birds, with 85? million years behind them show more variety as to shape
>(not color).
>

I would think that, from a phylogenetic point of view, the best that could
be offered is that it is equivocal as to what kinds of pupils dinosaurs
have based on the conditions in consecutive outgroups. Which leads to an
equally correct (in my view) way of reconstructing the pupils of dinosaurs;
to convey a more geeneral understanding to the uninitiated observer. For
example, a vertical slit *looks* like it belongs to a cold, calculating
hunter and so would be appropriate for theropods where as the more inocuous
round pupil gives a less threatening appearance that we would associate
with a herbivore. This method does rely, almost exclusively, on our
preconceptions of the nature of animals but a reconstruction of an extinct
animals is a scientific model laden with our preconceptions anyway. By
comparison, who ever really thinks that oxygen atoms are red and hydrogen
are blue, yet any model of a water molecule always depicts them this way.
Why? Because it fits our preconceptions and helps convey a whole bundle of
intellectual baggage in a simple format.

Enough pontificating.

Cheers, Paul

pwillis@ozemail.com.au