Maybe all the camels are wrong
September 27, 2010
Suddenly it’s camel season here at SV-POW! In the last post, Mike was having some doubts about how far back camels could get their heads. That got me curious, so here are the results of 45 minutes worth of Google Image Search.
This live baby camel (source) has its neck extended about as far as the presumably dead juvenile camel from the last post, so that pose is not just mechanically possible, but also achievable in life. Admittedly, this is a baby, so it might have a bit more flexibility than adults. But I doubt if it is really pushing things here, since I’ve seen adults get into more extreme poses than this.
This dromedary Bactrian camel [thanks to John Scanlon for the correction] (source) has its head back pretty close to the hump, but it’s hard to tell with all the hair. People trying to work out the normal neck postures of the members of KISS probably run into the same problem.
I think we should have a caption contest for this one (source). Not terribly informative from a figuring-out-what-the-bones-are-doing point of view, but I like it.
A kneeling camel, from Werner Herzog’s Even Dwarfs Started Small, described as “the only film whose all-dwarf cast gleefully commit acts of arson and vandalism, throw themselves at or on top of moving vehicles, flick through pornographic magazines, stage a mock religious ceremony with a crucified monkey and laugh themselves hoarse at a camel as it takes a dump” (source, for both photo and quote). What’s cool here is that the camel’s back is angled down at the front, but its neck and head posture are unchanged.
Same thing, this time in color, sans dwarf (source).
Now, none of these camels are maxing out because they don’t have their heads laying back on their humps, as shown in slide 9 of this talk by Kent Stevens (thanks to Steve O’C for the link, in a comment on the last post). Which prompted Mike to write:
Yes, I’ve seen the picture you allude to, with the dorsal surface of the camel’s head in contact with the hump. (In fact I am pretty sure that either John or Kent showed that picture at SVPCA.) I initially planned to photoshop the mounted camel’s cervicals into that position, but it just seemed too ludicrous to believe in, and I’ve come to suspect that this picture might itself be the work of photoshoppers.
Look kids, the argument from personal incredulity!
It’s not Photoshop. There are more photos like this, they’re just not easily available online (believe me, I tried). The one shown by Jeff Wilson in his Jobaria talk at SVP ’99 was of a whole live camel on location in the desert, not the same posed camel you can see in Kent’s talk. Also, I’ve seen camels do this at the circus.
And why is it so hard to believe that camels can get their necks back that far? As Mike pointed out in another comment, the anterior verts aren’t extended much at all in his Cambridge camel. If they have anything like the flexibility of the posterior cervicals, getting the head back against the hump ought to be a cinch.
I am starting to think that camels might be the most interesting mammals out there. The neck of the giraffe certainly looks like it is suspended from the withers, whereas camel necks aren’t connected by any straight-line ligament from the back of the head to what pathetic withers they have (meaning that they do have a nuchal ligament, but it can’t be working like a suspension bridge cable inside that curvy neck), and must be held in those ridiculous curvy poses by continuous muscular effort. But when you look at the cervicals, there are no neural spines at all through the middle of the neck! Not to mention the very flat zygs that look like they shouldn’t allow the poses in the first place. It’s like they’re defying us to make any sense of them.
Clearly, what we need to do is visit museums with complete but disarticulated camel necks that we can put in sandboxes and pose, like I did for the chicken and the infamous rabbit way back when. It’s no good taking photos of mounted skeletons and declaring that they’re in ONP. Zyg-by-zyg scrutiny often reveals that one or more joints is not in ONP (usually more, if the animal is mounted in anything like a normal lifelike pose), and the spaces between the centra are often filled with some weird goop that is supposed to look like intervertebral cartilage, or just left open as in the Cambridge camel. Here is another shot from that talk of Kent’s, of a camel neck supposedly in ONP, illustrating both problems.
In the same talk, Kent wrote that the zygs of the camel do allow the head-to-hump posture. That’s backed up by some Photoshopped images of the same mounted camel with the goop in between the verts. I have no doubt that the craniocervical system of the camel allows the head to touch the hump, because I’ve seen it with my own eyes. What I’d like to know is whether you could put a disarticulated camel neck in a sandbox and achieve the same pose without violently disarticulating the cervicals. The photos of the Cambridge camel suggest that either the zygs are going a lot farther past each other than is commonly assumed, or the intervertebral cartilage is allowing more separation of the centra.
In Kent’s talk at SVPCA he cited a pers. comm. from Kent Sanders and me at SVP ’98, that in playing with ostrich necks we could not get the zygs to completely disarticulate, and that the bone would break before that would happen. That’s true, that is what we found. But the really important part of what we found is that the zygs don’t stay parallel to one another. That is, in flexing and extending the neck, the cervical zygs don’t just slide past each other in the same plane, they can also hinge apart like the covers of a book. You’ll recall that the assumption in Stevens & Parrish (1999) was that the zygs maintained 50% overlap, but subsequent work (including work by them) has shown that much smaller overlaps are possible. My work with Kent Sanders on ostrich necks suggests that the problems of determining ROMs from bones are even worse, because the zygs can get to 20-25% overlap and then hinge open, so that only the very edge of one zyg is still in contact with the other. At that point it is meaningless to even talk about overlap. How you constrain that in your model, I have no idea.
Finally, I have a memory of Greg Paul saying years ago, possibly on the DML, that if you fed a camel into DinoMorph, it would crash the program. If anyone can find that quote, I’d be grateful. To my knowledge, that assertion has never been tested, although I think it would be an informative exercise for all parties and I would be most interested in the results.
Bonus Sauropod Image
Because it was a long dry summer (Gilmore 1932:pl. 6):
- Gilmore, C. W. 1932. On a newly mounted skeleton of Diplodocus in the United States National Museum. Proceedings of the United States National Museum 81, 1-21.
- Stevens, Kent A., and J. Michael Parrish. 1999. Neck posture and feeding habits of two Jurassic sauropod dinosaurs. Science 284: 798-800.