[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
RE: How Did Hadrosaurs Survive?
HP Tim Donovan wrote:
> >The above scenarios are speculative. But you see, these scenarios cannot
> >be refuted,
> But are dubious.
> and they offer an alternative to your "concrete" assertions on
> >tyrannosaur behavior
> Not a very credible one.
"_Any possible_ phylogenetic pattern can be 'reconstructed' if one uses
personal imagination, or its lack, as a proof."
-- Jan Zrzavý, italics in the original
Doesn't only hold for phylogeny. It holds for all science. As an example,
have a look
into today's Nature; there's a paper on the unsuspected ability of hawkmoths
colors even in dim starlight, 0.1 millicandela per square meter, when humans
completely color-blind. Who would have imagined?
> >Bottom line: We don't know enough (and probably will *never* know) to
> >reconstruct the behavior of tyrannosaurs in the type of detail you're
> I disagree.
Could you explain why, or is that under embargo...? :->
> > > But titanosaurs were armored,
> >Some were; maybe not all titanosaurs were armored, however.
Never having seen a titanosaur, I strongly suspect that all which lacked
& hypantra were armored because they needed to keep their backs straight
> The smaller ones, most likely to be targeted
> e.g. Saltasaurus, definitely were.
And why do you think so, if you haven't considered the above? No armor has
with the scanty remains of *Hypselosaurus*, for example, which was estimated
at 12 m
in length and lived alongside an undescribed abelisaur that was probably 11
> > > hadrosaurs were not. Unless an herbivore is gigantic, it should have
> > > armor or weapons if it attempted to stand its ground.
I try to imagine a hadrosaur's kick... should be very similar to a
> >Again, you do not *know* this. I'll repeat what I said: large size is a
> >potential *deterrence* against large predators.
> But hadrosaurs were not sufficiently large in relation to tyrannosaurs
> for a combative survival strategy to be credible in the absence of armor
> or weapons.
Hm... Is there a land animal alive that always fights and never
On the other hand, horses, which qualify as cursorial, are good fighters
and bite, so I think everything tries to fight if escape is otherwise
> > The massive strength of a
> >hadrosaur fighting for its very survival is
> >enough to *injure* an attacking tyrannosaur.
> Possibly, but the tyrannosaur had an advantage-it was clearly
> designed to fight and kill,
Was it also designed to _be fought_? I'm not so sure. A good kick in the
and the abdominal cavity is filled with dangerous bone splinters that pierce
gut... imagine the cruel details.
> the hadrosaur was not. Lacking weapons, but evolving
> hooves and keen senses, hadrosaurs would
> have fled, and fought only as a last resort.
So what? Does this mean such fighting was automatically unsucessful in the
> >An injured tyrannosaur is as good as dead if it can't chase
> >and bring down prey any more - and you yourself has argued that these
> >guys were fast predators. No tyrannosaur would want to risk serious
> >and debilitating injury.
This is part of the reason why the predator is _always_ at a disadvantage.
what an intro lecture in ecology says:
1. The life-dinner principle. The prey is running for its life. The predator
running for its dinner. Occasional mistakes are fatal for the former but not
latter. Therefore the selection pressure on the former is a lot stronger
than on the
latter. Consequently, the prey is always one step ahead of the predator in
evolutionary arms race (ignoring all potentially complicated cases such as
2. The prey is a moving target. As soon as the predator is adapted to a
of prey, the target moves, because those types of prey to which the predator
optimally adapted survive preferentially. Those that are common today will
die out or evolve in the future because the predator will adapt to them. It
the prey moving. Therefore it's hard to imagine that a predator kills off
under stable conditions. To the contrary, it favors the _preservation_ of
because it prevents strong competitors among the prey species to become
> Lions are occasionally injured and bereft of their ability
> to hunt, but they
Not the (severely enough) injured ones obviously.
> still prey upon healthy adult ungulates.
If they can get them. Certainly happens, but certainly less often than less
individuals being caught.
> >Much better to target old, young or sick individuals -
> >those least able to fight back - as Cliff said.
> There is evidence that tyrannosaurs attacked armored dinosaurs,
1. Everything happens. Lions do attack elephants and crocodiles. But how
enough for natural selection to kick in? :-S
2. What is that evidence?
> and perhaps ceratopsids,
While I personally don't doubt it, what's the evidence? One unhealed bite
> which are much more dangerous or tougher than
How do you define toughness? As the time of survival after a tyrannosaur
bite? As the
ability and willingness to fight, which would be the same as dangerousness?
> Also, if tyrannosaurs did not dare attack healthy adults, why
> did ceratopsids and ankylosaurs evolve greater size to match T. rex?
Interesting logic."why did [...] evolve greater size to match T. rex?" You
an answer, and this prevents you from posing the question "why did they
Did they evolve their greater size because *T. rex* pressed them to? Did
evolve it for other reasons, and *T. rex* evolved its size to stay one and
steps behind its prey?
_Is there a way we can tell in the first place, given that terrestrial
sediments from the time just before the onset of Hell Creek deposition are
NA?_ I strongly dispute this.
> The average adult size should not have changed
> if they were generally not targeted.
If predation pressure were the only possible reason for such a size
> > > What hadrosaur would be foolish enough to fight a predator of
> > > comparable size without any obvious weapons?
> >Ummm.... any hadrosaur that wants to stay alive
> would run away as fast as possible!
As long as possible. And then it would kick, bite, wriggle.
Forgive me if I sound a little frustrated. In the Altperdino list I've
topic and similar effects of Ultra... er, *T. rex* :-> for months.
questions in this e-mail are real and not rhetoric.
+++ GMX - Mail, Messaging & more http://www.gmx.net +++
NEU: Mit GMX ins Internet. Rund um die Uhr für 1 ct/ Min. surfen!
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
* ---REMAINDER OF MESSAGE TRUNCATED--- *
* This post contains a forbidden message format *
* (such as an attached file, a v-card, HTML formatting) *
* This Mail List at USC.EDU only accepts PLAIN TEXT *
* If your postings display this message your mail program *
* is not set to send PLAIN TEXT ONLY and needs adjusting *
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * *