News:2009 hadrosaur mastication study

In 2009, a study was released that analyzed mastication in hadrosaurid dinosaurs. The study was led by University of Leicester and conducted by paleontologist Mark Purnell and his colleagues in England. The results were published on July 30, 2009 in the Proceedings of the National Academy of Sciences.

The study focused on Edmontosaurus in particular, and was performed by analyzing the microscopic scratches that formed on hadrosaur's teeth as they fed. The scratches have been preserved intact since the animals died. The researchers say that the scratches reveal that the movements of hadrosaur teeth were complex and involved up and down, sideways and front to back motion.

Hadrosaurs had a hinge between the upper jaws and the rest of the skull, as opposed to a flexible lower jaw joint seen in other animals. This strongly suggests that as the hadrosaurs began to eat vegetation, the food in their upper jaws was forced outwards, flexing along this hinge so that the tooth surfaces slid sideways across each other, grinding and shredding food in the process. This hypothesis had originally been proposed 25 years ago during the beginning of the Dinosaur Renaissance, however lacked evidence to support it during the time. Now, these scratch patterns provide confirmation of this theory, as well as providing new insights into the paleoecology of hadrosaurs.

By analyzing the scratches on the teeth, the researchers also determined that small particles of grit, normal for vegetation cropped close to the ground, was present in the hadrosaurs diet.

This study contrasts that of one performed last year that analyzed the stomach contents of a hadrosaur and determined that they ate cut up conifer needles, leaves, bark and twigs.