A new dinosaur unearthed in Wyoming had such large teeth

that its mouth perpetually looked to be smiling a huge grin.

The dinosaur, described in the latest Journal of Systematic

Paleontology, is called Kaatedocus siberi, with its name deriving from Diplodocus and the Native American Crow word for "small." Diplodocus was yet another dinosaur with

a winning smile. This latest find was an early ancestor to that dino.


walked on four limbs, had a long neck and a whiplash tail, such as the famous Diplodocus did," co-author Octavio

Mateus told Discovery News.

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Mateus, of the Universidade Nova de Lisboa & Museu

da Lourinhã, is one of the world's leading paleontologists, and is particularly

known for his work on sauropods — iconic large, plant-eating dinosaurs with long

necks and tails. He has studied sauropods on four continents.


was one such dino. Its herbivorous diet helps to explain its "grin."


had a set of pencil-like teeth in the front part of the muzzle," Mateus

explained. "They were adapted for eating plants. As for many sauropods, because

those teeth were not adapted for chewing, Kaatedocus

probably ingested gastroliths or gizzard stones."

Mateus and an international team

studied the well-preserved remains of Kaatedocus.

Often quite a bit of artistic license is needed during reconstructions, but in

this case, even the skull makes evident the dinosaur's "smiling" appearance.



lived 150 million years ago, during the Late Jurassic period. A relative of Diplodocus, this dinosaur lived earlier

and was smaller. The vast majority of species from this dino family come from

the Jurassic Morrison Formation of the Western United States. In contrast, this

new dinosaur was found further north, suggesting that subsequent generations

slowly moved southward over time.

In addition to the smiling expressions, this family of

dinosaurs holds another memorable distinction: they apparently weren’t too


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Ke-Qin Gao, a researcher at Peking University's School of

Earth and Space Sciences, and colleagues reconstructed basic features of

dinosaur brains based on endocraniums, or the inside surfaces of dino skulls,

if these features survived in the fossil record.

Gao and his team used an Encephalization Quotient, or EQ, to

speculate upon the complexity, or lack thereof, of brain activity in dinosaurs.

The EQ is a ratio of brain mass to body size.

At the very bottom of the EQ ratings is Diplodocus, with a meager .05 EQ. One of the longest known

dinosaurs, Diplodocus could measure

around 90 feet in length. Twenty feet of that was neck, topped off with a tiny

head and an even tinier brain case. Its long tail could inflict some serious

damage to predators, though, as could a kick from one of its four sturdy legs.

Kaatedocus likely

had a similar EQ, but it managed to survive in an environment with a lot of

other formidable dinosaurs. According to Mateus, these included Barosaurus, Stegosaurus and large carnivorous Allosaurus.

In terms of the recent Wyoming discovery, Mateus said, "This species is smaller and

slightly older than other dinosaurs of the same family, it is important for

understanding the evolution of all Diplodocus-like


Dino buffs can see the remains of Kaatedocus. They currently are on display at the Museum of Jurassic

Aathal in Switzerland.

(Images: Octavio Mateus, Universidade Nova de Lisboa & Museu

da Lourinhã)