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"Will the (hadrosaur) circle be unbroken?"

>I didn't say that. A T. rex bite should be just as deadly on a hadrosaur.<
I remember a statement to the effect of Tyrannosaurus not wanting to prey on
ceratopsians because of their horns, and a refutation of unhealed bite
wounds on a Triceratops specimen showing that they were not preyed upon.

>I didn't say that; there is proof that tyrannosaurs ate juvenile hadrosaurs
but not hatchlings.<
Not sure what the proof is, but I would agree that they'd go after juveniles
over infants.

>I pointed to the absence of tyrannosaur teeth at hadrosaur nests as
evidence that tyrannosaurs didn't attack the nests or adult hadrosaurs
didn't fight back.<
At Egg Mountain in '98, I found an tyrannosaur tooth about 20cm away from a
nest site.

>Some NA titanosaur armor has been reported;<
Reference please?

>in any case Alamosaurus was far more massive than Tyrannosaurus and may not
have needed it-although
the ability to survive is not the same as invulnerability<
Of course; nothing is ever truly "invulnerable". But you can get pretty
close to it by being too big to be preferentially preyed upon.

>Do zebra and wildebeest herds regularly fight lions or flee, fighting as a
last resort?<
But they do fight, and fight pretty well, regardless of time during the
hunt. Hence the "equation" I had in the previous post Size+Herding=Good
Defense. I mention neither flight or fight in this equation.

>But T. rex initially represented a new and more effective predator, and
several Edmontonian herbivores evidently could not survive alongside it<
Maybe this is my biggest issue here: if Tyrannosaurus evolved in isolation,
or was introduced into NA from someplace else, I can see a population being
negatively effected. But, I see no evidence from my knowledge of
paleogeography, of any isolated areas where T. rex could evolve, without
hadrosaurs, and then "reinvade" the rest of North America/the northern

>Including lions.<
Yes, including lions, although they have litters between 2-6, whereas Zebra
and wildebeest have usually 1 offspring per cow.

>Or Edmontosaurus and lambeosaurs. There is a nice illustration on page 338
I was trying to compare generally contemporaneous animals, but none the less
I'd be interested to see this illustration. I don't have access to this
book. Can someone send a scan?

>I'll say.<
But you don't provide a reference, only derisive comments. I'll refer you to
HP Leahy's post, which I quote below here:
"In Gregory Erickson's chapter in The Scientific American Book of Dinosaurs,
he notes that bite marks are significantly more common on hadrosaurs than
ceratopsians, and that ankylosaur remains show no evidence of bite marks."
So perhaps I'm not as ill-informed as you may think.

>What other factor(s)? Didn't I already address your suggestion that
hadrosaurine competition was responsible?<
You dismissed it, citing that they had different feeding heights (which I'm
not sure there's much evidence for). Factors could include famine, disease,
competition for food/space/water, decreasing gene pool, hyperspecialization
(which leads animals to be less able to adapt), among others. All of which
are about as testable as your hypothesis.

>I just got the impression that the Hell Creek lambeosaur report may not
stand up.<
I got the impression that we shouldn't discuss it until its been fully

Student of Geology
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