Scientists have found that therizinosaurs defied the sterotype of sensory abilities of plant-eating animals. Their  exceptional sensory abilities - smell, hearing and balance - were well developed and might have affected or benefited from an enlarged forebrain, something typically associated with predators. 

Therizinosaurs are an unusual group of theropod dinosaurs which lived between 145 and 66 million years ago. Members of the group had evolved to be 23 foot long animals possessing 20 inch long, razor-sharp claws on their forelimbs, elongated necks and a coat of primitive, down-like feathers along their bodies.

were closely related to carnivorous dinosaurs such as Tyrannosaurus rex and Velociraptor, but despire their menacing appearance they were probably peaceful herbivores.

Palaeontologists studied the brain and inner ear anatomy of therizinosaurs using high-resolution CT scanning and 3D computer visualization to find out more about their sensory and cognitive capabilities and how these had evolved with the transition from meat- to plant-eating. The focus of the study was the skull of Erlikosaurus andrewsi, a 10-13 foot therizinosaur which lived more than 90 million years ago in what is now Mongolia. 

Lead author, Stephan Lautenschlager of Bristol's School of Earth Sciences said, "Our results suggest that therizinosaurs would have used their well-developed sensory repertoire to their advantage which, for herbivorous animals, must have played an important role in foraging, in the evasion of predators or in social complexity.

"This study sheds a new light on the evolution of dinosaur senses and shows it is more complex than we thought."

Co-author, Professor Lindsay Zanno of the North Carolina Museum of Natural History and the North Carolina State University agrees, saying "Once you've evolved a good sensory toolkit, it's probably worth hanging on to, whether you're hunting or being hunted." 

"Of course the actual brain tissue is long gone from the fossil skulls but we can use CT scanning to visualize the cavity that the brain once occupied and then generate 3D computer renderings of the olfactory bulbs and other brain parts," said  Fellow author Lawrence Witmer, Chang Professor of Paleontology at the Ohio University Heritage College of Osteopathic Medicine.  

This study has important ramifications for our understanding of how sensory function evolved in different dinosaur groups and whether it was developed as a response to their environment or simply inherited by their ancestors. In particular, in the light of the transition from dinosaurs to birds, these results should prove to be very interesting.