Sauropods still didn’t hold their necks in osteological neutral pose
September 19, 2010
I’m just back from SVPCA 2010 (the Symposium of Vertebrate Palaeontology and Comparative Anatomy), and what an amazing meeting it was. I think it was the best I’ve been to. That’s partly because I understand more of the talks these days — it’s the first time I’ve ever listened to every single talk, even all the mammal-tooth and fish-skull talks — and I learned something interesting and new from almost every one of them.
But as is so often the case, the best thing about the meeting was, well, meeting. I met with Matt and Darren for the first time in a year, which is always excellent. And for the first time, I met horizontal-sauropod-neck advocate Kent Stevens. Kent was there to present one of two talks on horizontal necks, and UK sauropod jockey John Martin presented the other. Their talks were part of a block of seven sauropod talks — it would have been eight had Michael Pitman not changed his scheduled sauropod-tail talk to a theropod-tail talk. Matt and I both made presentations, although Darren wasn’t able to because he didn’t know that he’d be able to come to the meeting until the last moment.
After that block of talks, Matt, Darren and I went off to lunch with Kent and Martin. Despite the lighthearted attempts of session moderator John Hutchinson to build the session up as a two-way fight, it was all rather peaceful and enjoyable. After lunch we all went to have our photos taken together in front of the Zoology Museum‘s giraffe skeleton:
As you can see, we were all very civilised and well behaved.
In all seriousness, it’s no secret that we SV-POW!sketeers are very much advocates of a raised habitual posture, and so that we strongly disagree with Kent and John. We had a lot of fun talking together, but we didn’t find that they presented any compelling new evidence in their talks. (You can read the abstracts of their talks, and indeed of mine and Matt’s, in the SVPCA abstracts book.)
The case for horizontal or near-horizontal habitual pose rests on two assumptions. First, that osteological neutral pose (ONP) was habitually adopted; and second, that we can know what ONP was. We still feel that both of these assumptions are false. We can’t know ONP because there is not a single sauropod neck skeleton anywhere in the world consisting of undistorted cervicals — and even if we knew what ONP was, it wouldn’t tell us much about what I am suddenly going to call mechanical neutral pose (MNP)[*], because we don’t know anything about the intervertebral cartilage. And we know that extant animals do not habitually adopt ONP because we have X-rays that show us how they habitually rest, and we know that they don’t match what you get by articulating bones.
[* either John or Kent made the point that ONP != MNP in his talk. I think they probably used a different name for MNP, but it eludes me for now. If anyone can remind me, I will switch to their terminology.]
So, anyway, it was a bit frustrating watching John’s talk, and seeing him show many photographs of live animals and claiming that their necks were in ONP, when we knew perfectly well that they were not — because necks lie. We fear he may have been tricked by the misleading soft-tissue outlines that mask the postures adopted by the neck skeleton in nearly all tetrapods. As an example, I give you the hoatzin, which happily was on display at the Zoology Museum as both a stuffed specimen and a skeleton:
Here’s another photograph from the astounding collection of the Zoology Museum (and some day I really ought to blog about the museum itself). I took this photograph of the neck of a camel with no specific agenda, but when I looked at it again today, one aspect leapt out at me:
Notice how very dramatically the third and fourth cervical central fail to contact, and the fourth and fifth. How uncomfortable this must be for the poor camel — its neck extended (or “dorsiflexed”) far, far out of ONP, to the point where the vertebrae drastically disarticulate. And yet we all know perfectly well that habitual pose for camels is much more extended than this, and many of us have seen photos of camels leaning their necks right back so that their heads are upside down, and they can rub the top of their head against their back. Just imagine what that does to the cervical articulations.
More on this subject another time. For now, I leave you with more from the Sauropod Neck Posture Working Group summit.