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Newly Discovered Dinosaur Had Giant Neck, Air-Filled Bones

James Owen
for National Geographic News
March 21, 2006
 
Scientists say they have found the fossil of a new species of ungainly dinosaur that had special air sacs in some of its bones to help support its massively long neck.

Living more than 100 million years ago in what is now Mongolia (map), the dinosaur belonged to a group of gentle, plant-munching giants called sauropods, the biggest animals ever to have walked the Earth.

Experts say what's most impressive about the dinosaur isn't its huge bulk but its 24-foot-long (7.5-meter-long) neck.

Paleontologists Daniel T. Ksepka and Mark A. Norell of the American Museum of Natural History in New York discovered the fossil in Mongolia's Gobi desert in 2002.

The partial fossil skeleton includes a single neck vertebra that measures nearly 2 feet (0.6 meters) in length.

This is bigger than the same vertebra found in fossils of Diplodocus—another, much larger four-legged sauropod that measured up to 90 feet (27 meters) in length.

The researchers conclude that the smaller dinosaur was oddly proportioned even for a sauropod.

Their analysis of the find is detailed in last week's issue of the museum's journal, Novitates.

God of Might

The newly described species is named Erketu ellisoni. Erketu, the god of might, was one of 99 deities from pre-Buddhist Mongolian tradition.

Erketu ellisoni's neck bones suggest that an interesting evolutionary strategy allowed the animal to support its long neck, the researchers say.

Computed tomography (CT) scans show that the dinosaur's vertebrae are filled with spaces that probably held small air sacs.

"The vertebrae aren't solid bone but honeycombed with chambers which were probably filled with air," Ksepka said.

"This was definitely helping to reduce the overall weight of the animal, particularly the neck," he said.

"You don't want a lot of weight up front—that would off-balance the animal."

"This honeycomb structure is an advanced feature which you see pretty high up in the sauropod evolutionary tree," Ksepka added.

The researchers also report that the tops of these neck bones were split into two parallel tracks, likely allowing room for a ligament that helped the dinosaur lift its neck.

Titanosaurs

"Research that's been done lately indicates that other, similar sauropods probably held their necks parallel to the ground," Ksepka said.

"We think this animal had a similar posture," he added.

"It may have had this long neck to easily graze over a large area rather than to reach to the very tip of a tree. Their teeth were well suited for stripping vegetation."

The dinosaur's fossil remains—a chest plate, two lower leg bones, and an ankle bone—link it to an advanced group of sauropods called titanosaurs.

Titanosaurs are thought to have been a highly successful dinosaur group, because their fossils have been found throughout the world.

Despite this, the rich fossil beds of Mongolia have yielded very few sauropod remains.

"They're rare in general in the Gobi desert, so this fossil is helping us see what kind of sauropods were around in an area which has yielded all these other different kinds of dinosaurs," Ksepka said.

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