The scientists analyzed the skull of 70-million-year-old fossils of the giant dinosaur Ampelosaurus, discovered in 2007 in Cuenca, Spain, in the course of the construction of a high-speed rail track connecting Madrid with Valencia.
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 Spainís National Museum of Natural Sciences, said.
The first sauropods appeared about 160 million years earlier than this fossil. For 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.