- Associated Press - Thursday, September 30, 2010

WASHINGTON (AP) - Dinosaur skeletons often are pieced together with leg bones nearly touching, no room left for cushiony cartilage because scientists don’t know how much they had. New research suggests some species might have had a foot’s worth.

Mammal limbs have knuckle-like projections on each end that fit together like puzzle pieces at a joint, coated with thin layers of cartilage to keep bones from rubbing.

But many dinosaurs’ limbs are rounded off, suggesting thick pads of cartilage. The bones also can contain grooves that University of Missouri anatomy professor Casey Holliday theorizes are evidence of blood vessels needed to nourish the cartilage.

His team tested the limbs of some of dinosaurs’ modern relatives, ostriches and alligators, to estimate how much cartilage their ancient ancestors might have had.

Bones stripped of cartilage were 4 percent to nearly 10 percent smaller, and each contained some characteristics similar to dinosaur bones that can create a cartilage signature, Holliday reported Thursday in the journal PLoS One.

Using that information, he calculated that certain dinosaurs would have had more cartilage than others _ enough that already huge sauropods like Brachiosaurus could have added another 12 inches of height.

Holliday is interested in how various species build healthy joints, a field that in turn might shed light on arthritis.

But for dinosaur specialists, it’s work that could impact efforts to understand how the creatures stood and moved, said paleontologist Matthew Bonnan of Western Illinois University, whose own work is reaching similar conclusions.

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