Recent research reveals new information on the evolution of dinosaur senses
Bristol, UK, 19. 12. 2012 - Therizinosaurs are an unusual group of theropod dinosaurs from the Cretaceous Period. Members of this group had evolved into up to 7 m (23 ft) large animals, equipped with more than 50 cm (20 in) long, razor-sharp claws on the forelimbs, elongate necks and covered by a coat of primitive, down-like feathers along their bodies. Although closely related to notorious meat-eating dinosaurs such as Tyrannosaurus rex and Velociraptor, and in spite of their bizarre appearance, therizinosaurs were probably more peaceful plant-eaters.
It is this paradox that inspired an international team of palaeontologists including Stephan Lautenschlager and Emily Rayfield of the University of Bristol, Perle Altangerel of the National University of Ulaanbaatar, Lindsay Zanno of the North Carolina Museum of Natural Sciences and North Carolina State University, and Lawrence Witmer of Ohio University to take the first close look inside the heads of these enigmatic dinosaurs. They studied the brain and inner ear anatomy of therizinosaurs using high-resolution CT scanning and 3D computer visualisation to find out more about their sensory and cognitive capabilities and how these had evolved with the transition from carnivory to herbivory.
The focus of the study was the skull of Erlikosaurus andrewsi — a 3-4 m (10-13 ft) large therizinosaur, which lived more than 90 million years ago during the Cretaceous Period in what is now Mongolia.
The new study on the brain anatomy of therizinosaurs, published in the journal PLOS ONE, reveals that the senses of smell, hearing and balance were well developed in this group and might have affected or benefited from an enlarged forebrain. The new findings came as a bit of a surprise to the scientists, as exceptional sensory abilities would be expected from predatory and not necessarily from plant-eating animals.
“Our results suggest that therizinosaurs would have used their well-developed sensory repertoire to their advantage,” said lead author, Stephan Lautenschlager of the University of Bristol, “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 that is more complex than we thought” explained Lautenschlager further. Zanno agrees. “Once you’ve evolved a good sensory toolkit it’s probably worth hanging on to, whether you’re hunting or being hunted,” she noted.
“Of course the actual brain tissue is long gone from the fossil skulls,” said study co-author Lawrence Witmer, Chang Professor of Paleontology at the Ohio University Heritage College of Osteopathic Medicine, “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.”
This study has important ramifications for our understanding 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.
This work was funded by a research fellowship to Stephan Lautenschlager from the German Volkswagen Foundation and grants from the National Science Foundation to Lawrence Witmer.
—University of Bristol, UK
Lindsay Zanno (USA)
Institutions: North Carolina Museum of Natural Sciences & North Carolina State University
“The Endocranial Anatomy of Therizinosauria and its Implications for Sensory and Cognitive Function” by Stephan Lautenschlager, Emily J. Rayfield, Altangerel Perle, Lindsay Zanno, and Lawrence M. Witmer. published in PLOS ONE.
Link to the paper: http://dx.plos.org/10.1371/journal.pone.0052289 
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Figure 1. Life and skeletal reconstruction of Erlikosaurus andrewsi, with magnified virtual models of the brain and inner ear (Stephan Lautenschlager, University of Bristol).
Figure 2. Fossil skull of the Cretaceous therizinosaur Erlikosaurus andrewsi (Emily Rayfield, University of Bristol).