His work has expanded in recent years to analysing feeding mechanisms of extinct vertebrates more generally,[4][5] exploiting microwear, including validation studies based on extant stickleback fish.

In 2009, Purnell conducted a study into the chewing methods and diet of hadrosaurids, a herbivore species of duck-billed dinosaurs from the Late Cretaceous period.

The study, which Purnell co-authored with paleontologist Paul Barrett and graduate student Vince Williams, was published on 30 June 2009 in the journal, The Proceedings of the National Academy of Sciences.

[7] By analyzing hundreds of microscopic scratches on the teeth of a fossilized Edmontosaurus jaw, the team determined hadrosaurs had a unique way of eating unlike any creature living today.

The study also found that hadrosaurs likely grazed on horsetails and vegetation close to the ground, rather than browsing higher-growing leaves and twigs.