Re: The absurdity, the absurdity (was: Cooperating theropods?)

[Chris Campbell <sankarah@ou.edu>]

Larry Dunn wrote:
> 
> From: Jack <jconrad@lib.drury.edu>
> 
> >Indeed, but it also depends upon how you define rational and likely.
> 
> I define it as "to be expected based on reasoning."  In the case of
> paleontology we have to rely on the fossil record and  to some degree on
> likely modern analogs to hypothesize about the behavior of these
> animals.

The problem with that idea is that there *are* no modern analogs.  These
animals are so different in form that you can't really compare them to
extant animals.
 
> >The evidence does not give any conclusive proof that _Deinonychus_ 
> >preyed upon the _Tenontosaurus_, but there cannot be proof that it didn't.
> 
> I don't think we should have Deinonychus hopping on top of Tenontosaurus
> simply because we can't prove that it didn't happen.  I think we should
> look at extant animals of similar weight differentials and judge from
> that whether it's a likely scenario.

But you have to look at more than weight differentials.  You also have
to look at likely hunting techniques, life history strategies, build,
and so on.  All of these things are very different from those of living
species, so we can't directly compare the two.
 
> >I just don't feel that it is healthy to completely disregard the 
> >idea.
> 
> But this isn't an idea that everyone's keeping on the back burner as a
> remote possibility.  It's accepted as a fact by many: "Raptorman," able
> to leap tall herbivores in a single bound.

I just can't see a reason to think it's that remote, though.  Those
claws couldn't have been used for anything other than slicing (they're
too well designed for that role), and the dromies couldn't use them on
anything other than big animals.  You've said it's ridiculous to think
that they'd lose three of their number in an attack, citing modern
mammals as evidence, but the comparison isn't valid.  Dromies layed eggs
and lots of 'em; this might let large numbers of them survive to
maturity, which would mean they'd be less likely to worry about
individual survival.  None of this proves a damn thing, of course, but
it does make the hunting idea plausible.
 
> >We find _T. rex_ teeth in ceratopsian bone as well, but
> >there is currently no data supporting _T. rex_ as a predator of
> >ceratopsians.
> 
> Well, who knows if T. rex actively hunted ceratopsians?  Certainly not
> me.  But it's not unreasonabe to assume that an animal of T. rex's size
> and probable strength would be able to hunt and kill ceratopsians
> without enlisting it into a gang.

True.  Also, it's not unreasonable to assume that Deinonychus hunted
Tenontosaurs with good success, and that the site under discussion was
just a freak occurrence.  Heck, they might have killed it without losing
a member and then got swept up in a flash flood or something.  
 
> >If owls should happen to go extinct in the future and a
> >paleontologist digs up owl coprolites with small mammals bones in them,
> >there will be no _conclusive_ proof that owls preyed upon small
> >mammals.  (How could they without teeth?)
> 
> Vertebrates generally hunt prey smaller than themselves.  We're thus
> able to entertain the likely possibility that the owls were hunting the
> small mammals.
> 
> But if you brought the owl fossil to me and suggested that it hunted
> deer in packs by dive-bombing the deer and tearing at them with their
> talons,  I'd have to disagree, even if you also brought fossil owl
> pellets containing venison.  Owls being what they were and deer being
> what they were, I'd look for another explanation (a more rational and
> likely one!) for the presence of the venison.

A fair point, but we also have to remember such things as hunting dogs
killing water buffalo, wolves killing bison and moose, lions killing
elephants, and so on.  These are not unusual occurrences, so we have to
keep an open mind about what the possibilities are, especially in light
of differences in build, probably life history strategies, and armament.
 
> >In several million years there may be no conclusive evidence that
> >wolves or lions or hyenas are pack hunters either.
> 
> Well, for the sake of discussion I'll agree, and then I'll push all of
> the other extant carnivores off the cliff too.  Are you saying that
> future paleontologists should then assume they were all pack hunters
> because there's no proof that they weren't?

I wouldn't, unless I found a site which had a bunch of them in one
place.  That alone argues that they might have been social, if not
necessarily pack hunters.  But think about it: given that sickle claw,
pack hunting would require no coordination at all.  All you'd need is a
"scream and leap" mentality and a will for mayhem, and you could take
down whatever you felt like.  Larger numbers just mean larger animals. 
They don't have to coordinate on the scale of the brighter lions and
wolves out there, they just have to leap onto their prey, claw away, and
have the presence of mind to jump off when the thing starts falling.
 
> No inconvenience at all.  I'm glad we're at last agreed that discussion
> of ant behavior has no place in this conversation!  Let us banish spunky
> little Formica from the discussion.

But can we keep intrepid beetles?  :)

Chris