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Author Interview: Kimi Chapelle & Massospondylus Skull Anatomy

Andrew Farke Dinosaurs Interview

I’m a huge anatomy geek, and love papers that figure and describe the nooks and crannies of skulls. The increasingly widespread use of digital scans, coupled with the unfettering of page and color limitations by online publishing, has instituted a new golden age of anatomical description. So, I was really thrilled to see a new paper by Kimi Chapelle and Jonah Choiniere recently in PeerJ.

The work here used CT (computed tomography) scans to look inside the skull of Massospondylus, a sauropodomorph dinosaur that lived nearly 200 million years ago in what is now South Africa. As a sauropodomorph, Massospondylus was an early member of the lineage that later gave rise to such iconic giants as Brontosaurus and Diplodocus. Massospondylus is also known from a number of spectacular fossils, which means that it is pretty important as a point of comparison for understanding early sauropodomorph evolution. The paper is a real “monster,” with wonderfully detailed descriptions, comparisons and illustrations of every single preserved skull bone for a single specimen of this beast.

To learn more about Massospondylus and this particular paper, I reached out to lead author Kimi Chapelle. Kimi is a Ph.D. student at University of the Witwatersrand; this project formed the core of her master’s thesis. Thank you, Kimi, for taking the time to respond!

Silhouette of <i>Massospondylus</i>, by Scott Hartman. CC-BY, via phylopic.org.
Silhouette of Massospondylus, by Scott Hartman. CC-BY, via phylopic.org.

I would argue that Massospondylus is probably the best known dinosaur that the general public has never heard of. What would you want someone who isn’t a dinosaur paleontologist to know about this animal?
Kimi Chapelle: I guess that I would like the general public in South Africa to know more about it. A lot of people don’t know that we even have dinosaurs in South Africa, let alone who Massospondylus was. It’s a really neat dinosaur with so many great specimens referred to it from the cutest embryos, to beautifully articulated juvenile hands, to complete large skeletons! It’s not the biggest of dinosaurs, “only” 4-5m long, but I still find it pretty cool, with its small head, long neck, giant thumb claws and bipedal posture. It’s also scientifically important because of where it sits on the phylogenetic tree of dinosaur evolution. It’s pretty old; in fact the eggs associated with it are some of the oldest known dinosaur eggs in the world. It’s definitely a proudly South African dinosaur, and something South Africans should be proud of in return.

What was the most surprising part of your work for you?
KC: Well, the skull in this paper is the first one I ever segmented [editor’s note–“segmenting” is the process of outlining structures on CT scans for construction of a digital model]. It was all pretty exciting. But I guess the most surprising part was the amount of detail we could extract on the braincase and inner ear (I have a thing for braincases).

Skull of Massospondylus, modified from Chapelle and Choiniere 2018.

The skull that you scanned is a beautiful specimen. What is its story? When and where was it collected? With so many nice fossils to choose from, why did you pick this one?
KC: There were several reasons. The first one is the fact that it is one of the nicer, more complete skulls we have available in our collections. Secondly, it’s a pretty perfect size: it’s big enough to assume that it is near adult, and small enough that we would get good resolution using our facility’s CT scanner. Finally, we tried scanning the neotype skull, but the contrast and quality of the scans weren’t as good as the ones used in the paper.

Processing hundreds of CT scan slices can get monotonous quickly. What did you do to keep yourself focused and productive during this phase of the research? (I listened to a ton of podcasts when I was in heavy segmentation phase as a Ph.D. student!)
KC: Well, I’m lucky because I actually really enjoy segmenting! I find it therapeutic. Sort of like paint by numbers except that the end result is a 200 million year old fossil that you’re the first to discover in such detail! It’s pretty neat. That being said, I listen to music and multitask doing other things because working with big scans can be frustrating as some steps take a while to load or process.

Is there anything that you didn’t include in the paper–perhaps an observation or an entertaining anecdote–that you wish you could have?
KC: Spinning skulls! We have this ongoing joke in the lab that anyone who presents on data from CT scans has to have a spinning skull video somewhere in their presentation, otherwise it doesn’t count. But the STL file is a good substitute. Information-wise, we’ve been working on this paper for a while, so I think we covered what we wanted to.

Teeth of Massospondylus in the jaw, as revealed by CT scan. Modified from Chapelle and Choiniere 2018.

Citation

Chapelle KEJ, Choiniere JN. (2018) A revised cranial description of Massospondylus carinatus Owen (Dinosauria: Sauropodomorpha) based on computed tomographic scans and a review of cranial characters for basal Sauropodomorpha. PeerJ 6:e4224. https://doi.org/10.7717/peerj.4224

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