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THE BIPED/TRIPOD ISSUE
Seems I missed quite a bust-up on rearing in sauropods, with Ken
Carpenter and Greg Paul bringing ground sloths and sthenurine
kangaroos into the debate. A paper I recommend if you are interested
in any of this is FARINA, R.A. 1995. Limb bone strength and habits in
large glyptodonts. LETHAIA 28: 189-96.
Without getting myself into legal trouble by mailing out the abstract,
Farina estimates the masses of large glyptodonts and calculates
athletic ability based on bone and muscle masses (using
R.M. Alexander's formula). Interestingly, the femora show higher
athletic indicators - even when supporting the entire weight of the
animal - than humeri in the quadrupedal stance, and Farina proposes
that performance of strenuous bipedal locomotor activity was possible.
Glyptodonts may have been able to defend themselves in a more active
way than traditionally guessed, therefore, and Farina also suggests
bipedal display in intraspecific confrontations. Darren Tanke might be
interested to hear that healed fracture marks are actually quite
common in glyptodonts (OTOH, he's probably already aware of it)
(discussed in Ferigolo 1992).
What's more interesting to historical dinosaurologists is that Farina
seemingly drew somewhat on the ideas of Uncle Bob, comparing the
proposed side-step and tail-swing of a large glyptodont with a similar
action in a stegosaur. He furthermore suggest that such aggressive
behaviour may also have been employed by ankylosaurs (is that not
going a little _too_ far?).
"We're _very_ unhappy"
"What do you expect, you're dead!"
[ Betelgeuse Betelgeuse Betelgeuse! Sorry, Darren, I couldn't
resist ;-) -- MR ]