Hairy Museum of Natural History

Well, here’s just the sort of story to shake me out of my posting hiatus. A team of researchers led by Dr. David Varricchio have just announced the discovery of a hypsilophodont dinosaur that dug burrows and cared for its young in dens.

In a new paper, Varricchio et al. describe Oryctodromeus cubicularis, “digging runner of the lair,” from the remains of three individuals, and adult and two juveniles. The authors note that the fossils were found within a sinuous sandstone body that crosscuts three layers of a completely different type of mudstone. This indicates that the three Oryctodromeus were preserved deep within a sediment-filled burrow, and the mixed age of the specimens suggests that the burrow was a den where Oryctodromeus cared for its young.

There is every reason to believe that Oryctodromeus dug these burrows itself. The relative dimensions of the burrow match what an animal the size of an adult Oryctodromeus would make. And while the overall proportions of its skeleton suggest it was a better sprinter than tunneler, there are key details that suggest Oryctodromeus was quite capable of excavating a cozy little home. Its beak was solidly fused and expanded in the front, perhaps an adaptation to loosen or scoop out soil. Its shoulder girdle was remarkably robust compared to other hypsilophodonts, providing leverage for powerful forelimb muscles used in digging. The hips and base of the tail were also stoutly reinforced, allowing it to brace itself while tunneling.

Some of these features occur in other Montanan hypsilophodonts, such as Orodromeus and Zephyrosaurus, which appear to be the closest relatives to Oryctodromeus. Varricchio et al.’s careful study and description of the Oryctodromeus fossils and their surrounding sediments has given us insight into a newly discovered dinosaurian behavior, and suggests that Montana may have been home to a mid-Cretaceous radiation of burrowing hypsilophodonts.

Further reading:

Varricchio, D. J., Martin, A. J., and Katsura, Y. 2007. First trace and body fossil evidence of a burrowing, denning dinosaur. Proceedings of the Royal Society B: Biological Sciences. FirstCite early online publishing.

Padian, K. 2007. Dinosaurs digging deeper. Proceedings of the Royal Society B: Biological Sciences. FirstCite early online publishing.

The press release (with images) from Montana State University.

New Scientist has a good article, as does News in Science.

—Matt Celeskey.

File under: Cretaceous, Dinosaurs, Recent Discoveries.