Biggest dinos had tennis ball-sized brains

Researchers analysed the skull of 70-million-year-old fossils of the giant dinosaur Ampelosaurus, discovered in 2007 in Cuenca, Spain.

The reptile - a sauropod - had a long-neck, long-tail and was herbivorous, making them the largest creatures ever to stride the Earth.

Ampelosaurus was a kind of sauropod known as a titanosaur, many if not all of which had armour-like scales covering their bodies, 'LiveScience' reported.

Sauropod skulls are typically fragile, and few have survived intact enough for scientists to learn much about their brains.

By taking scans of the interior of their skull via CT imaging, the researchers developed a 3-D reconstruction of Ampelosaurus' brain, which was not much bigger than a tennis ball.

"This saurian may have reached 15 meters (49 feet) in length; nonetheless its brain was not in excess of 8 centimetres (3 inches)," study researcher Fabien Knoll, a paleontologist at Spain's National Museum of Natural Sciences, said in a statement.

The first sauropods appeared about 160 million years earlier than this fossil.

"We don't see much expansion of brain size in this group of animals as they go through time, unlike a lot of mammalian and bird groups, where you see increases in brain size over time," researcher Lawrence Witmer, an anatomist and paleontologist at Ohio University, said.

"They apparently hit on something and stuck with it