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:

Sauropod Neck Posture Working Group, 2010 meeting.  From left to right: Darren Naish, Matt Wedel, John Martin, Mike Taylor, Kent Stevens.

As you can see, we were all very civilised and well behaved.

The Sauropod Neck Posture Working Group carefully considers all points of view in a detached, professional and mature manner.

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:

Hoatzin (Opisthocomus cristatus), stuffed specimen and skeleton.  Note the extraordinarily long cervical skeleton, almost entirely unreflected in the live animal.

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:

Head and neck of dromedary camel (Camelus dromedarius) UMZC H.14191, in right lateral view, with disarticulated C3/C4 and C4/C5 joints.

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.

Hey!  That hurt!

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Necks lie

May 31, 2009

Since we’re spending a few days on neck posture, I thought I’d expand on what Mike said about bunnies in the first post: in most cases, it is awfully hard to tell the angle of the cervical column when looking at a live animal. Because necks lie.

horse neckTake this horse (borrowed from here). You can see that the external outline of the neck, which is what you would see in the living animal, is pointed in a different direction than the cervical column.

horse neck 2And here’s why. Many mammals carry their heads and necks so that the cranio-cervical joint is up high and the head is angled down from it. At the base of the neck, tall neural spines on the anterior thoracic vertebrae support the nuchal ligament, which lifts the body profile far above the cervical vertebrae. Basically, the cervicals run from the lower or middle part of the neck at its base to near the top of the neck at the head end.

horse neck 3This mismatch holds no matter how the neck and head are oriented. When the animal lowers its head to graze, the cervical column is still angled up relative to the apparent angle of the neck defined by its dorsal and ventral margins.

But if you think that’s bad, you ain’t seen nothin’ yet.

Budgie skeleton 480

In most of the smaller birds, like this budgie (from Evans 1969:fig. 5-6) the neck is much longer and more flexible than you would think based on the external profile. And check out the mismatch between the cervical column (in front) and the trachea (behind). That’s not drawn incorrectly; the trachea is outside the bundle of neck muscles that encloses the vertebrae, and it is free to slide around all over the place, and does so in many birds.

Also note that while the neck is extended past vertical, the extension occurs in the middle of the neck, not at the shoulder. The neck actually goes down from the craniocervical joint, not up. My guess is that there is a lot of this in climbing taxa that hold their torsos elevated. Vultures come to mind here, too. A useful reminder that in natural history we are usually dealing with norms, not laws.

colomba_livia 480

In the pigeon, note again the fact that the mid-cervicals are angled up much more sharply than is the external profile of the neck. In fact, the external profile of the neck is angled forward while the mid-cervicals are angled backward. This excellent reconstruction is from this page, which has several others which also show that necks lie.

Vidal-et-al-1986-fig5a-v2

Lest anyone think that the pigeon was either an outlier or a case of artistic embellishment, here’s yet another rabbit, this time from Vidal et al. (1986: fig. 5a). Again, the mid-cervicals–actually, almost all of the cervicals–are angled backward, but the neck as a whole is pointing slightly forward.

As an aside, I think possibly it has blown some people’s minds that we have used so many rabbits as examples, both in the paper and in our blog coverage. What can we say? Rabbits are awesome.

greater-flamingo-ng 480

Of course not all necks lie. With flamingos, what you see is what you get.

Giraffes: 20 feet of reticulated irony

Herd-of-reticulated-giraffe

Let’s see here: necks not vertical.

Male-masai-giraffe-right-and-juvenile---showing-colour-variation

Necks not vertical.

Masai-giraffe-feeding-from-tall-tree

Trying . . . very . . . hard . . . and . . . just . . . getting . . . to . . . vertical!

(I know it looks like the neck is just slightly less than vertical, but remember that necks lie, and the cervical column is steeper. In this animal, you could drop a plumb bob from the ear and it would track the course of the cervical vertebrae just about perfectly.)

VidalEtAl1986-fig2-cat

Cat, not trying at all: cervical column past vertical (Vidal et al. 1986: fig. 2).

Vidal-et-al-1986-fig5bcRat, taking its ease (top): cervical column vertical. Guinea pig, straight chillin’ (bottom): cervical column past vertical (Vidal et al. 1986: fig. 5 b and c).

Here’s the irony: for  practically as long as sauropod neck posture has been contentious, giraffes have been held up as THE example of the most extreme (dude!) elevated neck postures out there. But in fact giraffes have to really reach to achieve vertical cervical postures that “ordinary” animals like cats, rats, guinea pigs, chickens, and, yes, rabbits, reach or exceed all the time.

Good paleobiology has to start with good biology. It’s high time that the sauropod neck posture debate got a reality infusion. Giraffe necks are extreme in terms of length, but not in terms of posture.

Speaking of sauropods…

All right, you’ve suffered long enough. Here’s your sauropod vert. Care to guess what it is?

cervical

References

  • Evans, H.E. 1969. Anatomy of the budgerigar; pp. 45-112 in Petrak, M.L. (ed.), Diseases of Cage and Aviary Birds. Lea and Febiger, Philadelphia.
  • Vidal, P.P., Graf, W., and Berthoz, A. 1986. The orientation of the cervical vertebral column in unrestrained awake animals. Experimental Brain Research 61: 549­-559.