Scientists find first dinosaur brain tumour

"Although we haven't conclusively identified the type of brain tumour found in this specimen, we are sure the tumour impaired the mobility of the dinosaur," said Rachel Reams, a veterinary pathologist at Eli Lilly and Co. who participated in the research.

"It almost certainly affected its balance and locomotor function," she added.

The announcement was made in Indianapolis by the Children's Museum of Indianapolis and the Black Hills Institute of Geological Research.

Evidence of the tumour was found in a fossil of a 25-foot-long predator called Gorgosaurus, a meat-eater closely related to Tyrannosaurus rex, the announcement said. The fossil was discovered in 1997 at the Two Medicine Formation in western Montana's Teton County.

Peter Larson, co-founder of the Black Hills Institute, said in an interview that the tumour was likely cancerous, "but we can't say that for sure. ... We do know that it was life-threatening, and if it did not directly cause death, it led up to it."

He said the finding is significant because it is the first brain tumour found in any kind of fossil -- dinosaur or otherwise -- and it shows that problems like brain tumours "have been around basically forever."

The ball-shaped mass was about two inches in diameter in a brain that was about half the mass of a human brain. The tumor took up almost all of the cerebrum, the part of the brain that processes higher thought, and was pressing against the brain stem, Larson said.