Dinosaur Park

Cretaceous Roll Call: Nodosaurs

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Nodosaurs were short-legged, stocky, and very wide plant eating dinosaurs. Along with their cousins the ankylosaurs (think club tails), they were among the most well-armored animals to ever appear on Earth. Nodosaur backs, legs, and tails were studded with bony knobs, called scutes, which were embedded in the skin. Their heads had built-in helmets, made from outgrowths of bone from the skull itself.

With so much extra weight to carry around, nodosaurs were not very fast or agile. Instead, they relied on their heavy armor for protection against predators. The armor was also probably used for show: large spikes made nodosaurs look wider and taller than they really were. Since nodosaur fossils are usually found in watery environments, it’s possible that they spent much of their time in rivers and ponds, like hippos today.

Two nodosaur species are known from Maryland. Propanoplosaurus is known from a single fossil – an almost perfectly preserved baby (called a scuteling) discovered near College Park in 1997. Priconodon was named by O.C. Marsh in 1888, based on teeth found at or near the Dinosaur Park quarry. A small number of bones have been attributed to this taxon since then, but Priconodon teeth remain the most commonly found nodosaur fossils in Maryland. These ridged, spade-shaped teeth are deceptively small. While Priconodon teeth are typically less than a centimeter across, when compared to more complete nodosaur skulls found elsewhere they imply an animal that was 30 feet long – at least.

Nodosaurs are known from every continent except Africa. They first evolved in the early Cretaceous Period, and in fact, the oldest known nodosaur is Maryland’s own Propanoplosaurus. However, Propanoplosaurus is surprisingly advanced. This suggests that there is a stem lineage of nodosaurs somewhere in North America or Europe that we haven’t discovered yet. We expect that Maryland fossils will play a part in solving the mystery of nodosaur origins.

References

Carpenter, K. Ankylosaurs. In The Complete Dinosaur, Second Edition. Eds. Brett-Surman, M.K., Holtz, T.R., Farlow, J.O., and Walters, B. Bloomington and Indianapolis, IA: Indiana University Press.

Kirkland, J.I., Alcala, Luis, Loewen, M.A., Espilez, E., Mampel, L., and Wiersma, J.P. 2013. The Basal Nodosaurid Ankylosaur Europelta carbonensis n. gen., n. sp. from the Lower Cretaceous (Lower Albian) Escucha Formation of Northeastern Spain. PLOS ONE 8:12.

Marsh, O.C. 1888. Notice of a new genus of Sauropoda and other new dinosaurs from the Potomac Formation. American Journal of Science 135:89-94.