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Re: a question for the tyrannosaur experts was: How Did Hadrosaurs Survive?




From: "Cliff Green" <dinonaut@emerytelcom.net>
Reply-To: dinonaut@emerytelcom.net
To: "dinosaur mailing list" <dinosaur@usc.edu>
Subject: a question for the tyrannosaur experts was: How Did Hadrosaurs Survive? Date: Sat, 26 Oct 2002 19:28:11 -0600



> > BTW, My theory has just as much credibility as any one elses, seeing
> >that, once again, no one has seen
>
> I don't think so; it seems far more likely that hadrosaurs fled, and
> fought only as a last resort. If hadrosaurs had regularly attempted to
stand
> their ground, weapons and or armor would have been selected for. Instead
> they evolved keen senses and longer legs, and "hooves".


Dear Tim and list,

I think that perhaps I wasn't clear on all this. I definately agree that
duckbills first line of defense was probably flight. I think that flight is
the natural initial reaction for just about any living thing, including
humans, when threatened.

No. Some dinosaurs were well armored and/or armed; the raison d'etre for such defenses is to enable a defender to stand its ground.




I remember using that very defense mechanism
myself, in grade school, as I was being targeted for elimination by the
school neanderthaloids.
My entire point in this whole debate is that I think that duckbills, in
general, where tougher then you give them credit for.


     I said that at least one type had large spikes across it's back and
tail. I think these spikes would have made it harder for a theropod to
bite down on a duckbill from above, into the spine.
>
>    It would have bitten into the upper thigh or flanks.

    Have you seen a tyrannosaurs launch this method of attack on a
regular basis? I'm not saying they didn't or wouldn't, I'm just stuck on
Your "It would have" as an absolute.

Tyrannosaurids had a horizontal posture so probably wouldn't have attacked from above into spines, and striking soft tissue would probably cause a quicker death from hemorhaging.



> > > By running away, but not (all hadrosaurs could escape a new > >predator > >with > > > consummate senses and speed.

What "New" predator are you talking about? Are you saying that
tyrannosaurs were a newly indroduced species to the West,

>
>   Tyrannosaurus or its immediate ancestor appears absent in the lowlands
in
> the late Edmontonian period and probably evolved in the well inland
> environments, perhaps in response to Alamosaurus, as Starkov suggested.

    I thought daspletosaurus from the Judith River Formation was a
Tyrannosaur ancestor.

But it lived at least 4 million years before T. rex, whose closest ancestor must have been something like T. bataar, which was roughly contemporaneous with the late Edmontonian fauna.


Btw, I should have added in my response to Rob Gay, who mentioned a study suggesting Albertosaurus was faster than T. rex: If longer legs conferred no advantage, why were they selected for among tyrannosaurs and hadrosaurs by the Lancian? Why did T. rex monopolize the top predator niches, including prey which fled; why didn't Albertosaurus persist like the cheetah alongside the lion if it were faster?


And Again, I heard a lecture by Dan Chure in 1994
saying that The Dinosaur National Monument, in Northeast Utah, had
braincases And teeth of what appeared to be primitive tyrannosaurs from the
Morrison.These fossils have been attributed to Stokesosaurus.         Am I
mistaken on this? Haven't there been recent discoveries of more primative
tyrannosaurs such as eotyrannis (Sp.) as well?

    HEY! all you list Theropod experts. Can any of you be of assistance?

Thanks.

Cliff Green


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