Smithsonian.com

The head of Diplodocus, on a reconstruction at the Utah Field House of Natural History. Photo by the author.

At about 80 feet long, an adult Diplodocus would have required a huge amount of food to fuel its bulk. But how did these huge dinosaurs actually eat? We know from the anatomy of their skulls, and their peg-like teeth, that Diplodocus and other sauropods were not capable of chewing. They did not stand among the Jurassic’s fern-covered floodplains, grinding away. These gargantuan dinosaurs clearly plucked food, then swallowed the mouthfuls whole, but what did Diplodocus dinner habits actually entail?

Paleontologist Mark Young and co-authors have just released a new study in the journal Naturwissenschaften on the different ways Diplodocus could have collected plant food. After creating a virtual model of a Diplodocus skull to investigate the different stresses and strains created by three different feeding behaviors, Young and colleagues investigated what happened to the skull during a normal bite, when the Diplodocus tried to strip leaves from a branch, and when the sauropod tried to strip bark from a tree.

Not surprisingly, the Diplodocus experienced little stress in the simple bite model. The dinosaur was perfectly capable of opening and closing its jaws vertically on plants without any major stress. This was true of branch-stripping, too. The skull of Diplodocus easily coped with the low levels of stress created by biting on a branch and pulling to remove the vegetation from the plant. As Young and colleagues point out, the dinosaur did not shear through the plants, but instead detached the soft parts of the vegetation from the tougher branches or stems of the parent plant.

When the scientists modeled what would happen when Diplodocus tried to strip bark from trees, though, they found that the dinosaur’s skull was not well-suited to the strains involved. Diplodocus specialized on the soft parts of plants, and didn’t scrape its teeth over tree bark.

The same technique may help us better understand why there were so many other sauropods lived alongside Diplodocus. Indeed, the sauropods of the Morrison Formation include Diplodocus, Apatosaurus, Barosaurus, Brachiosaurus, and Camarasaurus, each with more or less different skulls. (Haplocanthosaurus was another contemporary sauropod, although we have no idea what this dinosaur’s skull looked like.) Perhaps, by modeling how the skulls of these different sauropods responded to feeding stresses, we can parse what sort of foods they preferred and gain some insight into why so many giants lived at the same time.

Reference:

Young, M.,  Rayfield, E., Holliday, C., Witmer, L., Button, D., Upchurch, P., Barrett, P. (2012). Cranial biomechanics of Diplodocus (Dinosauria, Sauropoda): testing hypotheses of feeding behaviour in an extinct megaherbivore Naturwissenschaften DOI: 10.1007/s00114-012-0944-y