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Re: ANKYLOSAUR CLUBS *
On Sat, 17 Feb 1996, Ronald Orenstein wrote:
> A question; would the degree of horizontal vs vertical movement suggest that
> an ankylosaur would have been aiming mainly at an attacker's legs (with, I
> suppose, the aim of throwing it off balance) rather than generally flailing
> away at it (in which case rotation in three dimensions would be more useful)?
By "attacker" do you mean a predator? The thing would have been
the most useful piece of offensive weaponry an ankylosaur had against a
predator, but it seems a good question as to whether it couldn't be used
against other ankylosaurs. (I don't buy the stuff about the tail being
too stiff. Why have those massive caudal ribs to attach muscles to if
you're not going to be able to use those muscles?)
I think we pretty much agreed recently that rhinos use their
horns mainly against predators, not each other. It seems you could make a
similar case for a Centrosaurus. Other animals have horns primarily for
intraspecific combat- bighorns and giraffes(ossicones). Then there seems
to be everything in between- male elephants are dependent on their tusks
for securing females, but don't they also use them against predators?
Triceratops probably used those horns for defense, but scars also show
up on frills from other Triceratops.
The blunt weapons, though, would seem to imply that intraspecific
combat is the main driving force behind their evolutiuon, and perhaps
some are also of use against predators. If they were primarily
anti-predatory devices, selection should cause them to become sharp and
pointed like a rhinos horns. Cases like these among the dinosaurs seem to
be Pachyrhinosaurus, Pachycephalosaurus, and the Ankylosaurs. (in the
case of Ankylos and Pachyrhinosaurus, selection has favored the
development of nonlethal weapons like clubs and blunt horns over lethal
ones like shoulder spikes and sharp horns). Pachycephalosaurus had
something that was basically a solid bone helmet- a high-impact
head-butting device. Now, I believe that last time the issue came up, it
was mentioned that Ankylosaur clubs were filled with spongy tissue.
Somebody mentioned a similar, "foamy" texture for the Pachyrhinosaurus
nasal boss, and suggested low-impact nose-butting.
I'd guess that they were both primarily used for low-impact
combat, and perhaps throw in Shunosaurus and the Diplodocids as usingtheir
for intraspecific combat. Imagine giraffes: the males swing their heads
and thump each other in the sides with their ossicones. Then imagine
something similar, but with the tails of Ankylosaurus, Shunosaurus, and
Diplodocus. (Don't try imagining this style of butting with
Pachycephalosaurs, though, or your imaginary pachies might all break their
Those are high-impact structures, made of pretty solid bone, and probably
meant for head-to-head collision) The sexual dimorphism is a bit tricky.
Only male giraffes have ossicones
(I think...). Pachyrhinosaurus has the structure in all individuals, but it
appears much larger among some (presumably males). Some animals have horns
in both, of course. But for most dinosaurs, we don't have enough
individuals to get a good look at sexual dimorphism and see how that
prediction bears out.
anyways, those are my thoughts, hope its not too long-