Once more, I’m going to start recycling some of those dinosaur texts written for the defunct field guide (for the back-story on that project see the ornithomimosaur article here). This time round, I’ll get through some of the ceratopsians [adjacent skull reconstruction from wikipedia, and based on an image by Jaime Headden].
One of the most poorly known ceratopsians, Udanoceratops tschizhovi was a Mongolian species from the Santonian-Campanian Djadokhta Formation. Named in 1992 by Sergei Kurzanov, the holotype consists of an incomplete skull (the frill and everything around the orbital region are reconstructed in the image above) and associated partial skeleton. A juvenile specimen has also been identified. The skull is approximately 60 cm long, so this was a reasonably large animal, with a total length estimated at 4 m. Its short, deep skull is highly distinctive, and it lacks the peg-like premaxillary teeth present in Protoceratops. It also differs from these genera in having a particularly deep lower jaw that was curved along its length. Most studies find Udanoceratops to be most closely related to to the North American taxa Leptoceratops and Prenoceratops (Chinnery & Weishampel 1998, Xu et al. 2002, Chinnery 2004, Makovicky & Norell 2006), in which case it’s a member of Leptoceratopsidae [Udanoceratops life restoration below from wikipedia; by Arthur Weasley].
It seems that at least some leptoceratopsids looked insane: Greg Paul reconstructed Leptoceratops, and found that it had a proportionally gigantic skull and a really short tail (Paul 1996). Dale Russell’s better known reconstruction (Russell 1970) is far less extreme and more widely known, but it’s a composite based on scaled data from more than one specimen. Unfortunately, the precise reasoning behind either reconstruction has yet to be provided: a very quick look at the data and images provided by Sternberg (1951) indicates that Paul’s reconstruction is more correctly proportioned. Back to Udanoceratops: I found the photo below here. It’s labelled as Udanoceratops but differs substantially from the holotype skull (much smaller nostril, jugal flange when one is lacking in Udanoceratops, deeper anterior end of dentary, etc.) – so, what is it?
One last thing: Tereschenko (2008) argued that Udanoceratops was facultatively aquatic. For reasons that are never really explained in the paper, Tereschenko apparently assumed amphibious or aquatic habits in most non-ceratopsid ceratopsians: I think because the long neural spines on the caudal vertebrae were taken to evidence regular swimming habits, and because the fossils of these dinosaurs are often associated with lakes or ponds. The paper is extremely flawed and the conclusions are almost certainly erroneous. However, it remains unknown why at least some non-ceratopsid ceratopsians possessed such tall neural spines on their caudal vertebrae. A role in display has been suggested – is it coincidental that Psittacosaurus (at least) had quill-like bristles on its tail?
Refs – –
Chinnery, B. 2004. Description of Prenoceratops pieganensis gen. et sp. nov. (Dinosauria: Neoceratopsia) from the Two Medicine Formation of Montana. Journal of Vertebrate Paleontology 24, 572-590.
Chinnery, B. J. & Weishampel, D. B. 1998. Montanoceratops cerorhynchus (Dinosauria: Ceratopsia) and relationships among basal neoceratopsians. Journal of Vertebrate Paleontology 18, 569-585.
Makovicky, P. J. & Norell, M. A. 2006. Yamaceratops dorngobiensis, a new primitive ceratopsian (Dinosauria: Ornithischia) from the Cretaceous of Mongolia. American Museum Novitates 3530, 1-42.
Paul, G. S. 1996. The Complete Illustrated Guide to Dinosaur Skeletons. Gakken.
Russell, D. A. 1970. A skeletal reconstruction of Leptoceratops gracilis from the upper Edmonton Formation (Cretaceous) of Alberta. Canadian Journal of Earth Sciences 7, 181-184.
Sternberg, C. M. 1951. Complete skeleton of Leptoceratops gracilis Brown from the Upper Edmonton Member on the Red Deer River, Alberta. Bulletin of the National Museum of Canada 123, 225-255.
Tereschenko, V. S. 2008. Adaptive features of protoceratopoids (Ornithischia: Neoceratopsia). Paleontological Journal 42, 273-286.
Xu, X., Makovicky, P. J., Wang, X.-l., Norell, M. A. & You, H.-l. 2002. A ceratopsian dinosaur from China and the early evolution of Ceratopsia. Nature 416, 314-317.