Brain size of the biggest dinosaurs was as small as a tennis ball.

Recent research have claimed that an advanced member of the largest group of dinosaurs ever on Earth, had a relatively very small brain.

Skull of seventy million years old fossils of the dinosaur Ampelosaurus, discovered in 2007 in Cuenca, Spain was examined by the scientists.

The reptile was a sauropod, long-necked, long-tailed herbivores that were the largest creatures ever to stride the Earth.

More specifically, Ampelosaurus was a kind of sauropod known as a titanosaur, many if not all of which had armorlike scales covering their bodies. Sauropod skulls are typically fragile, and few have survived intact enough for scientists to learn much about their brains.

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

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

The first sauropods appeared about 160 million years before than this fossil. Many years, scientists have wondered how the largest land animals ever lived with such tiny brains.

Their computer model also revealed the ampelosaur had a small inner ear.The findings are published online in the journal PLOS ONE.