The Cambridge Camel is Just Plain Wrong
September 21, 2010
Since I posted my photograph of the Cambridge University Zoology Museum’s dromedary camel in the last entry, I haven’t been able to get it out of my mind. Here it is again, this time with the background removed:
You’ll remember from last time that the thing that struck me most powerfully about it was the huge disarticulations between the centra of C3, C4 and C5. [Stevens and Parrish (2005:fig. 10.1A) illustrated the articulated cervical column of a dromedary camel Camelus dromedarius in osteological neutral pose, and it comfortably approximates life posture; but its vertebrae are very different from those of this specimen. I don't know what to make of this. Are there dromedary subspecies? If so, they are very different from each other; if not, then the individual variation is pretty amazing.]
The Cambridge mount made me wonder how the neck of that specimen would look if we moved it down into neutral pose — that is, keeping the zygapophyses maximally overlapped as they are in the mount, but bringing the centra together at the same time. I tried it in GIMP (a free equivalent to the better-known PhotoShop), and here is the result:
Let’s be clear that photoshopping vertebrae is an inexact science at best: I am working here from a single photograph taken carelessly as one among a hundred taken opportunistically in a museum too awesome not to photograph; I can see the vertebrae only from one angle; judging the maximal zygapophyseal overlap is error-prone.
Still, even taking all of these factors into account, I found this pose striking. It left me very much wanting to find a published osteology of the camel with better multi-view figures of the cervical vertebrae. Sadly, it seems like there isn’t anything like that (though if you know better, PLEASE say so in the comments!) But my search led me inevitably to tetrapod savant Darren Naish, and he pointed me to Maziersky (2010), a book review which includes the following photo:
Judging by the odd way the camel is propped up on a table, this is a dead animal being posed rather than a live one adopting a posture voluntarily, but it does appear that this is at least a pose that the mechanics of the animal allow. And that got me thinking about how the vertebrae must be arranged to allow this. Here’s the best I’ve been able to come up with:
In comparison with the mounted skeleton’s pose, this re-articulates cervicals 3 and 4; but 4 and 5 remain horribly disarticulated, and the 5-and-6 and 6-and-7 pairs are now also in this state.
(A reminder is due again here that what I am doing is an approximate and error-prone process. No doubt I got the maximal possible zygapophyseal disarticulation wrong in several places, for example. But even allowing for that, I find this pretty amazing.)
If you’re wondering why the two earlier images had so much blank space at the top and this one has so much to the right, it’s because I made them all the same size and shape. This means that if you open all three images in different browser tabs, then tab between them, you should see the neck neatly moving between the three different poses. For those of you too lazy or technophobic to do that, here is a superposition:
Habitual posture (i.e. when the animal is not eating or drinking or otherwise doing anything in particular with its head) is somewhere above the mounted pose, but less extended than the raised pose shown by Maziersky.
What does all this tell us?
Nothing very encouraging, I’m afraid. Even allowing for the vagaries of photoshopping images of museum mounts, it’s apparent that something very weird is going on in this camel’s neck, such that even a pose well below the habitual one requires extensive vertebral disarticulation. Assuming that, like me, you don’t believe the vertebrae really are disarticulating in life, we can only conclude that it is useless to try to reach conclusions about neck posture based on osteology alone. We need to understand the soft-tissue systems — especially the articular cartilage — as well.
Stevens and Parrish (1999:798) stated that “in vivo, muscles, ligaments, and fascia may have further limited movement [i.e. beyond the restrictions imposed by maintaining zygapophyseal overlap]; thus, the digital manipulations reported here represent a ‘best case’ scenario for neck mobility.” Although this seems intuitively appealing, evidence including but not limited to the Cambridge camel shows that the opposite is actually the case: in at least some taxa, and maybe all, soft tissue enables necks to be more flexible, not less, than the bones alone suggest.
Folks, we’re flying blind. Until we start to understand the soft tissues in the necks of extant critters — especially the intervertebral cartilage, but I bet that’s not the whole story — we really have no idea how to interpret the bones.
Come on, neontologists! Teach us about intervertebral cartilage!
- Maziersky, David. 2010. Anatomy of the Dromedary: Illustrating the world’s first atlas of camel anatomy. Halcyon 45:5-6 (June 2010).
- Stevens, Kent A., and J. Michael Parrish. 1999. Neck Posture and Feeding Habits of Two Jurassic Sauropod Dinosaurs. Science 284:798-800.
- Stevens, Kent A., and J. Michael Parrish. 2005. Neck posture, dentition, and feeding strategies in Jurassic sauropod dinosaurs. pp. 212-232 in: Virginia Tidwell and Ken Carpenter (eds.), Thunder Lizards: the Sauropodomorph Dinosaurs. Indiana University Press, Bloomington, Indiana. 495 pp.
Special bonus archosaur-rich artwork
Check out John Conway’s obscenely brilliant infinite-zoom Jehol video. (Well, a lot of people have been calling it infinite zoom, but it’s clearly finite. Still, it’s at least Very Big Zoom.) A lot of jaws dropped at SVPCA in Cambridge when John was showing this off. While you’re at it, you might like to read the interview with John at Dave Hone’s Archosaur Musings. Dave’s interviewed quite a few palaeoartists now, but John has more to say than most of them, and it’s well worth a read.
Special bonus horror story
While I was emailing with Darren about camels, he told me that John Hutchinson had recently acquired a camel at the RVC, and suggested that I ask to be present at the dissection of the neck. I contacted John only to be told: “Just got the feet; had no time to get the rest, sadly. Notice came at a bad time for my group, as it tends to do. It is now incinerated.” John also told me at SVPCA of a hippo that was recently incinerated because he couldn’t get to the zoo to collect it within 24 hours. Graaaggh! It’s a tragedy the dead animals that go to waste.