Welcome Kaatedocus: this is how to illustrate a sauropod
December 20, 2012
A couple of days ago, a paper by Tschopp and Mateus (2012) described and named a new diplodocine from the Morrison Formation, Kaatedocus siberi, based on a beautifully preserved specimen consisting of a complete skull and the first fourteen cervical vertebrae.
Unfortunately, the authors chose to publish their work in the Journal of Systematic Palaeontology, a paywalled journal, which means that most of you reading this will be unable to read the actual paper — at least, not unless you care enough to pay £27 for the privilege.
So you’ll just have to take my word for it when I tell you that it’s a fine, detailed piece of work, weighing in at 36 pages. It features lavish illustrations of the skull, but we won’t trouble you with those. The vertebrae are illustrated rather less comprehensively, though still better than in most papers:
It should be immediately apparent from these lateral views that the vertebra are rather Diplodocus-like. But the hot news is that there is a great raft of free supplementary information, including full five-orthogonal-view photos of all fourteen vertebrae!
Here is just one of them, C6, in glorious high resolution (click through for the full awesome):
Now, folks, that is how to illustrate a sauropod in 2012! The goal of a good descriptive paper is to be the closest thing possible to a proxy for the specimen itself, and you just can’t do that if you don’t illustrate every element from multiple directions. By getting this so spectacularly right, Tschopp and Matteus have made their paper the best illustrated sauropod description for 91 years. (Yes, I am talking about Osborn and Mook 1921.)
It’s just a shame that all the awe-inspiring illustrations are tucked away in supplementary information rather than in the paper itself. Had the paper been published in a PLOS journal, for example, all the goodness could have been in one place, and it would all have been open access.
Is Kaatedocus valid?
There’s a bit of a fashion these days for drive-by synonymisation of dinosaurs, and sure enough no sooner had Brian Switek written about Kaatedocus for his new National Geographic blog than comments started cropping up arguing (or in some cases just stating) that Kaatedocus is merely Barosaurus.
It’s not. I spent a lot of time with true Barosaurus cervicals at Yale this summer, and those of Kaatedocus are nothing like them. Here is Tschopp and Mateus’s supplementary figure of C14:
And here is a posterior vertebra — possibly also C14 — of the Barosaurus holotype YPM 429, in dorsal and right lateral views:
Even allowing for a certain amount of post-mortem distortion and “creative” restoration, it should be immediately apparent that (A) Barosaurus is much weirder than most people realise, and (B) Kaatedocus ain’t it.
There may be more of a case to be made that Kaatedocus is Diplodocus — but that’s the point: it there’s a case, then it needs to be actually made, which means a point-by-point response to the diagnostic characters proposed by the authors in their careful, detailed study based on months of work with the actual specimens.
There seems to be an idea abroad at the moment that it’s somehow more conservative or sober or scientific to assume everything is a ontogenomorph of everything else — possibly catalysed by the Horner lab’s ongoing “Toroceratops” initiative and subsequent cavalier treatment of Morrison sauropods — maybe even by the Amphidocobrontowaassea paper. Folks, there is no intrinsic merit in assuming less diversity. Historically, the Victorian sauropod palaeontologists of England did at least as much taxonomic damage by assumptions of synonymy (everything’s Cetiosaurus or Ornithopsis — whatever that is) as they did by raising new taxa. The thing to do is find the hypothesis best supported by evidence, not presupposing that either splitting or lumping is a priori the more virtuous course.
Morrison sauropod diversity
As we’ve pointed out a few times in our published work, sauropod diversity in the Kimmeridgian-Tithonian in general, and in the Morrison Formation in particular, was off-the-scale crazy. There’s good evidence for at least a dozen sauropod genera in the Morrison, and more than fifteen species. Kaatedocus extends this record yet further, giving us a picture of an amazing ecosystem positively abundant with numerous species of giant animals bigger than anything alive on land today.
Sometimes you’ll hear people use this observation as a working-backwards piece of evidence that Morrison sauropods are oversplit. Nuh-uh. We have to assess taxonomy on its own grounds, then see what it tells us about ecosystem. As Dave Hone’s new paper affirms (among many others), Mesozoic ecosystem were not like modern ones. We have to resist the insidious temptation to assume that what we would have seen in the Late Jurassic is somehow analogous to what we see today on the Serengeti.
Hutton’s (or Lyell’s) idea that “the present is the key to the past” may be helpful in geology. But despite its roots as a branch of the discipline, the palaeontology we do today is not geology. When we’re thinking about ancient ecosystems, we’re talking about palaeobiology, and in that field the idea that the present is the key to the past is at best unhelpful, at worst positively misleading.
But isn’t the Kaatedocus holotype privately owned?
You’ve had two sermons already, I’m sure we can all agree that’s plenty for one blog post. I will return to this subject in a subsequent post.
Sermon doesn’t even get started.
Tschopp, Emanuel, and Octávio Mateus. 2012. The skull and neck of a new flagellicaudatan sauropod from the Morrison Formation and its implication for the evolution and ontogeny of diplodocid dinosaurs. Journal of Systematic Palaeontology. doi:10.1080/14772019.2012.746589