Biggest Dinos Had Tennis Ball-Sized Brains

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Though the plant-eating dinosaur Ampelosaurus was among the largest to walk the Earth, it was equipped with a puny brain.
O. Sanisidro

An advanced member of the largest group of dinosaurs ever to walk the Earth still had a relatively puny brain, researchers say.

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.

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

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, told LiveScience. "They apparently hit on something and stuck with it -- expansion of brain size over time wasn't a major focus of theirs."

For years, scientists have wondered how the largest land animals ever lived with such tiny brains. "Maybe we should flip that question on their end -- maybe we shouldn't ask how they could function with tiny brains, but what are many modern animals doing with such ridiculously large brains. Cows may be triple-Einsteins compared to most dinosaurs, but why?" Witmer said.

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