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Re: How would Tyrannosaurus approach a Triceratops?

Aidan Karley (aidan_karley@yahoo.co.uk) wrote:

<I see the reasoning, but I've just been doing some poking around with my specs
and eyeballs to work out that the only experimental animal I have available
(H.sap) has about a 90deg field of view per eyeball, so with an optic axis
oriented at 45deg to the body/ skull axis, the actual fields of view of each
eye would barely overlap. Obviously subject to assumptions about the angular
width of field of view in T.rex, and the amount of yaw of their eyes in their
sockets. would the scleral plates constrain this? they're anchors for
eye-moving muscles, aren't they?>

  Note that tyrannosaurs are not really well known for their scleral rings,
such that, unlike birds, their eyes were free from these physical constraints.
Indeed, while the orbits faced 45 degrees, it is unknown in which direction the
eyeball naturally oriented. In keeping with previous replies, these eyeballs,
the size of tennis balls as recounted by Currie's refutation of Horner's "bad
eyesight" idea, would have been able to orient over the snout in which the
narrow nasal would decrease the angle between fields of vision. The nasal
becomes, even accounting for the lateral addition of the lachrymal in the
posterior end of the snout in front of the eyes, narrower than the breadth of
the snout should the head (most unlikely) be held as if the basal line (ventral
margin of the premaxilla to distal quadrate condyles) were horizontal. This
would have increased the overlap by some 15-20 degrees.

  As for blind stumbling around: vision is notoriously movement based in
herbivores, which rely on olfaction to detect their food, kin, etc. Indeed, if
*T. rex* were like a turkey vulture and used it's nose more than it's eyes, it
would still rely on vision to find food; the detection of prey availability
(the smell of dead flesh, blood, etc.) in distance is required for indeed most
predators who would like an easy kill or food source. If it were so bad at
seeing that it was nosing it's way through life, it would more likely be an
herbivore, now wouldn't it?


Jaime A. Headden

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)

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