Sauropod hypothesis: the base of the tail of sauropods was always more less horizontal. That is, the keystoning of the sacrum predicts the angle of the back from the ground. Prove me wrong @mike and @ScottHartman.

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@john @mike I think tail angle was horizontal or less. I don't think any tetrapods with tail-based restractors habitually held the tail above horizontal for biomechanical reasons.

@john @mike I agree the tails were not arched into the air, even in the most keystoned of sacra, so it sets a minimum angle of the back. That's actually how I've been doing my new (or reposed) sauropod skeletals for 4 years or so now.

@john @mike And once people stop doing the GSP unguligrade pes posture the limbs tend to line up with such a pose (I switched all my sauropods to that 5-6 years ago, but I didn't say much outside of an SVP presentation about it).

@ScottHartman @mike I had noticed the shift in your skeletals, but i wasn’t sure whether you were deliberately not arching the tails, or whether it was a natural consequence of the other changes.

@john It was the confluence of several things - assuming tails don't go past vertical, getting a more realistic degree of flexion in the knee and ankle, and some small refinement to pectoral girdle placement. It's in my stack of like 3 dozen blog posts I have a planning folder for but never actually finished.

@ScottHartman @john Oh, so it looks like we (gather gently) disagree on this.

@mike @john We do here. Turns out sauropod tails go horizontal when I made other (IMO improved) assumptions about foot and pectoral posture, so the synergy with the biomechanical improvement makes it a strong argument to me. Also, while hadrosaurs and prosauropods once got the "tails arched in the air" treatment, those are clearly wrong, so with it not being normal to dinosaurs and there being no extant analog I think the "tail-arching up" model is coasting on social inertia at this point.

@ScottHartman @john On this, I'm happy to defer to you. I've got no dog in the scapula-position fight, and no real opinion on whole-body posture. (I'd love to read a paper on it, though, HINT HINT.)

@mike @john it's on the pile of papers I need to start after finishing up publishing the rest of my dissertation.

@ScottHartman @john When you get to it, drop me a line if you're interested in collaboration. (No offence taken if not!)

@mike @john sounds good. The rib chapter is really foundational to this project anyhow.

@john @ScottHartman Well, the keystoning is real and ubiquitous. But I am more inclined to think that the base of the tail was typically inclined somewhat upwards. See discussion at

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