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Re: Saurischia and Ornithischia pelvis

Being able to rest on it seems to be as much a question of the right orientation of the bone as it is of having the right surface, because the loaded bone should be approximately under the center of mass.

Of course having generally more gracile pubes without the massive distal expansion doesn’t help, but both the right positioning and the right shape and robusticity are required if the bone is supposed to be used this way.

An ornithischian with an opistopubic condition wouldn’t be able to effectively use its pubis to support its weight while resting, even if it had a pubic boot. The longer part of the bone is sticking out caudally, there’s no way it could get it under the center of mass unless it was sitting on it near-vertically (and caudal flexibility probably wouldn’t have allowed even that).

I don’t know how important an ability this was for saurischians (though that they readily lost it to adapt for herbivory suggests it wasn’t very important), but if it was used the way that was suggested, the plesiomorphic orientation of the pubis would help fulfill an actual function in at least some saurischians, as opposed to being totally useless.

On 13.07.2015 23:05, tholtz wrote:
And I think people are conflating the actual question (orientation) with
the not-related issue of a pubic boot (a distal expansion of the pubis,
regardless of the orientation). The original poster asked about the
position of the pubis.

Yours sincerely,

Darius Nau