An unusual British dinosaur has been shown to have a skull that functioned like that of a fish-eating crocodile.
Natural History Museum Baryonyx animatronic model
Dr Emily Rayfield at the University of Bristol used computer modelling techniques to show that while Baryonyx was eating, its skull bent and stretched in the same way as the skull of the Indian fish-eating gharial - a crocodile with long, narrow jaws.
Baryonyx, was nearly 9m long and had 96 serrated teeth. It also had two huge 30-cm-long front claws, perhaps used to scoop fish from the water. Baryonyx, which belonged to a family called spinosaurs, lived in the early Cretaceous period, which was around 125 million years ago.
Emily Rayfield holding a gharial skull at the Natural History Museum.
The dinosaur specimen studied by Dr Rayfield, Baryonyx walkeri, was discovered near Dorking in Surrey, UK in 1983 by William Walker who was an amateur collector. The specimen was named after him in 1986 by Alan Charig and Angela Milner.
Partially-digested fish scales and teeth were found in the stomach region of the animal along with a dinosaur bone, suggesting that at least some of the time this dinosaur ate fish.
'It had a very unusual skull that looked part dinosaur and part crocodile,' said Dr Rayfield, 'so we wanted to establish which it was more similar to, structurally and functionally - a dinosaur or a crocodile.'
Fossil Baryonyx snout
The team used an engineering technique called finite element analysis that reconstructs stress and strain in a structure. The Baryonyx skull bones were CT-scanned at Ohio University, USA, and digitally reconstructed so that the internal anatomy could be viewed.
The team then compared digital models of the snouts of a Baryonyx, a theropod dinosaur, an alligator and a fish-eating gharial, to see how much each snout stressed during feeding.
Baryonyx animatronic claw
The results showed that the eating behaviour of Baryonyx was markedly different from that of a typical meat-eating theropod dinosaur or an alligator, and was actually most similar to the fish-eating gharial. Since the bulk of the gharial diet consists of fish, Dr Rayfield's study suggests that this was also the case for Baryonyx.
Dr Angela Milner from, dinosaur expert at the Natural History Museum, who first described the dinosaur and is co-author of the paper, said, 'I thought originally it might be a fish-eater, and Emily's analysis, which was done at the Natural History Museum, has demonstrated that to be the case.'
Dr Milner adds, 'The CT data revealed that although Baryonyx and the gharial have independently evolved to feed in a similar manner, through quirks of their evolutionary history their skulls are shaped in a slightly different way in order to achieve the same function. This shows us that in some cases there is more than one evolutionary solution to the same problem.'
Mr William Walker holding Baryonyx claw
The unusual skull of Baryonyx is very elongate, with a curved or sinuous jaw margin as seen in large crocodiles and alligators. It also had stout conical teeth, rather than the blade-like serrated ones found in meat-eating dinosaurs, and a striking bulbous jaw tip, or 'nose', that bore a rosette of teeth, more commonly seen today in slender-jawed, fish-eating crocodilians such as the Indian gharial.
The research is published in the latest issue of the Journal of Vertebrate Paleontolology.