The National Geographic Channel ran a documentary called “Bizarre Dinosaurs” way back in October 2009, but just yesterday I got a copy of the DVD, which has inspired this post. I appeared on the show in different contexts, but primarily talking about Nigersaurus, indeed a dinosaur to which the term “bizarre” applies.
A Mesozoic Cow
Nigersaurus is Paul Sereno’s baby. It’s one of a whole bunch of remarkable animals he’s discovered in many years of fieldwork in Cretaceous deposits in the Sahara Desert of Niger in Africa. Nigersaurus is a rebbachisaurid diplodocoid sauropod dinosaur that presented so many unusual attributes that Paul assembled a team of researchers to try to make some sense of its bizarreness. This team included his longtime collaborator and former student Jeff Wilson, Jeff’s student John Whitlock, and myself, among others. We published our results in 2007 in the open-access, online journal PLoS ONE (Sereno et al., 2007). Paul gave a press conference to introduce Nigersaurus at the National Geographic HQ in Washington, DC, and there were lots of press reports surrounding this “Mesozoic cow” with its “lawnmower mouth.” Paul and I even did an NPR interview and eventually, of course, the “Bizarre Dinosaurs” show (it’s quite a ride when you sign on for Cirque du Sereno!). As we in WitmerLab often try to do, we put up a Project Page on our university site, with a common language summary and all kinds of other resources such as movies and 3D PDFs. We uploaded a pile of movies to our YouTube channel, too.
Brain size: if you can’t say anything nice, then…
My role in the project was to help figure out what the brain and sensory attributes of this beast might tell us. Ryan Ridgely and I have had NSF grants since 2003 to study the brain and ear regions of dinosaurs and their relatives. Paul Sereno knew of our work on the sauropod dinosaurs Diplodocus and Camarasaurus (Witmer et al. 2008), so he invited us on. Ryan also did the 3D visualizations of the skull and teeth used in the article and the Nat Geo show, based in part on Tyler Keillor’s skull restoration. The brain cast of Nigersaurus was interesting enough, showing that Nigersaurus was like other sauropods in having almost absurdly small brains: about half the size we would expect for a modern-day reptile of the same body size…and frankly, our expectations for modern-day reptiles with regard to brain power aren’t very high!
Inner ear & hearing: Exsqueeze me? Baking powder?
The brain cast is pretty informative, but the delicate little inner ear, buried deep within the skull, provides some key information. The inner ear is involved with the senses of hearing and balance. The hearing part is the cochlear duct, projecting down like a finger from the bottom of the inner ear. In most sauropods, the cochlear duct is pretty short (Witmer et al. 2008), but in Nigersaurus it’s so short that we concluded that the reception of air-borne sounds wasn’t very important. By our standards, it had poor hearing.
Inner ear & alert posture: pay attention
Another surprising finding is what the upper, balance part of inner ear told us about the head posture of this crazy sauropod. [Note: My using the words “posture” and “sauropod” together in the last sentence has automatically caused red lights and sirens to go off in the offices of the guys over at SV-POW.] It turns out that one of the semicircular canals of the inner ear gives us an indication of head posture—but not just any posture, the posture of the head when animals are alert, aware, and paying attention. Of course animals can put there heads in all kinds of postures, but evidence from diverse land-living animals shows that when animals are super-vigilant, they tend to hold their heads in a stereotyped manner that presumably maximizes their sensory capabilities (see Witmer et al. 2003, Hullar 2006, Witmer & Ridgely 2009). That “alert posture” corresponds to holding the head such that the lateral semicircular canal is horizontal. Ryan and I had looked at alert posture in other sauropods, and Camarasaurus had a somewhat downturned posture and Diplodocus was strongly downturned (Witmer et al. 2008), but what we found in Nigersaurus made us scratch our heads and wonder whether our slick alert-posture trick was defective. The alert posture of Nigersaurus had the head pointing straight down! No other animal does this! We soon realized it made perfect sense given both the trend in sauropods and the unique “lawnmower” feeding apparatus (Sereno et al. 2007). Lots of animals have alert postures that are very similar to their feeding postures, particularly animals that spend a lot of their time feeding, which must have been true for sauropods, too.
Among my proudest moments…
Okay, you’ve been very nice, patiently wading through arcane minutiae of dinosaur anatomy. So what’s the connection to Optimus Prime, the noble Autobot leader of Transformers fame? The Nat Geo “Bizarre Dinosaurs” documentary was narrated by Peter Cullen, who also has been the voice actor for Optimus Prime from the 1980s TV show to the present movie series. In the video clip above, not only does Optimus Prime Peter Cullen describe our research, but (at 2:28, to be precise) he utters my name. Yes, Optimus Prime spoke my name! Thank you, Nigersaurus, for making that happen.
Hullar, T. E. 2006. Semicircular canal geometry, afferent sensitivity, and animal behavior. Anatomical Record 288A:466–472.
Sereno, P. C., J. A. Wilson, L. M. Witmer, J. A. Whitlock, A. Maga, O. Ide, and T. A. Rowe. 2007. Structural extremes in a Cretaceous dinosaur. PLoS ONE 2(11): e1230. doi:10.1371/journal.pone.0001230.
Witmer, L. M. and R. C. Ridgely. 2009. New insights into the brain, braincase, and ear region of tyrannosaurs, with implications for sensory organization and behavior. Anatomical Record 292:1266–1296.
Witmer, L. M., R. C. Ridgely, D. L. Dufeau, and M. C. Semones. 2008. Using CT to peer into the past: 3D visualization of the brain and ear regions of birds, crocodiles, and nonavian dinosaurs. Pp. 67–88 in H. Endo and R. Frey (eds.), Anatomical Imaging: Towards a New Morphology. Springer-Verlag, Tokyo.