Want a big flocculus? Try a pterosaur

Pterosaurs, the extinct flying reptiles, had the largest neural system for processing balance information ever seen in a vertebrate. It probably allowed them to perform complex aerobatic manoeuvres while keeping their gaze firmly centred on their prey.

Studying fossil pterosaur skulls is extremely difficult because they are so delicate. Taking casts of their skull cavities to determine the shape of their brains is especially tricky. So instead Lawrence Witmer, at Ohio University in Athens, and his colleagues used X-ray CT scans to built up three-dimensional images of the brains of two species.

One striking finding was that the animals, Rhamphorhynchus muensteri and Anhanguera santanae, both had a massive flocculus. This is the brain region that integrates balance information from various parts of the body and sends the information on to the eyes. This brain region occupied 7.5 per cent of the pterosaurs' total brain mass - in birds the organ occupies only one to two per cent.

This is remarkable because birds themselves have a large flocculus compared to other animals. "It is just ridiculously large in pterosaurs," says Witmer.

Posted by David on October 29, 2003 2:52 PM