Dec 03, 2013 08:06 AM EST By Staff Reporter, UniversityHerald Reporter

An international team of researchers discovered that keratin-covered beaks evolved in some theropod dinosaurs not just to replace teeth but to balance the skull during feeding. The beak also reduced the risk of bending and deformation of the skull.

"It has classically been assumed that beaks evolved to replace teeth and thus save weight, as a requirement for the evolution of flight.  Our results, however, indicate that keratin beaks were in fact beneficial to enhance the stability of the skull during biting and feeding," Lead author Dr Stephan Lautenschlager of Bristol's School of Earth Sciences said in a statement.

For the study, the researchers closely examined the skull of Erlikosaurus andrewsi, a 3-4m (10-13ft) large herbivorous dinosaur, which belonged to the clade 'therizinosaur'. Andrewsi lived in present Mongolia more than 90 million years ago during the Cretaceous Period.  

Using digital models including high-resolution X-ray computed tomography (CT scanning) and computer simulations, Lautenschlager and Dr Emily Rayfield of the University of Bristol with Dr Perle Altangerel (National University of Ulaanbaatar) and Professor Lawrence Witmer (Ohio University) found that part of its snout was covered by a keratinous beak.

"Using Finite Element Analysis, a computer modelling technique routinely used in engineering, we were able to deduce very accurately how bite and muscle forces affected the skull of Erlikosaurus during the feeding process.  This further allowed us to identify the importance of soft-tissue structures, such as the keratinous beak, which are normally not preserved in fossils," Rayfield, Co-author and Reader of Palaeobiology at Bristol said.

Keratin is a tough material that is found in the beaks of birds and turtles, and in horns, nails, claws and hooves.

"Beaks evolved several times during the transitions from dinosaurs to modern birds, usually accompanied by the partial or complete loss of teeth and our study now shows that keratin-covered beaks represent a functional innovation during dinosaur evolution," Witmer, Chang Professor of Paleontology at the Ohio University Heritage College of Osteopathic Medicine said.

The finding has been published in the journal PNAS (Proceedings of the National Academy of Sciences).

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