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Re: doin' the theropod nod

Mickey Rowe wrote:

> Relative to most other animals, birds
> have huge eyes.  That is, their eyes take up a larger percentage of
> their skull volume than do the eyes of other animals.  One of the
> things that birds have largely reduced in order to make space for
> their eyes are the extra-ocular muscles, the muscles that move the
> eyes within their orbits.
> By keeping its head in one place as it moves its
> body forward relatively slowly, and then jerking its head forward to
> another temporarily fixed position the bird thus does the best it can
> to keep its retinal image stable while still allowing the animal to
> move
(snip again)
> I would suggest that most dinosaurs -- even most theropods -- did *not*
> "do the pigeon

If that is the case, do you think there is an equation we could work here:
If a detailed study were done measuring the orbit and cranial volumes of all
known contemporary birds, there would be a difference across the board in
the eyeball/skull ratio of all these different genera.  On a line chart with
x marked as eye volume and y as skull volume, it may turn out that when x =
10% of y, the head bobbing would be very slight, while at 15% becoming more
obvious and by 20% would be fairly exxagerated and so on? it may even be
possible to document the forward and aft bobbing motion of the birds in
millimetres (if you're metric) and plot a linear increase of the bob to
coincide with the increasing size of the eyes relative to the skull.  We may
find out that the bobbing starts over an exact percentage.  Either way, a
similar study of theropod orbis/crania ratios would soon tell us which ones
bobbed and which didn't (and/or by how much).  That way we could tick off
the "theropod nod" as hard fact.  After all, the less inference in this
business, the better, right guys?

Samuel Barnett