A fossilized dinosaur foreleg being scanned by laser at Drexel University for 3-D printing. Drexel University image.

For all the digging of dinosaur fossils, all the magnificent reconstructions in museums  and all the research that has been devoted to them, the great beasts remain mostly a mystery to us, and paleontologist Kenneth Lacovara of Drexel University in Philadelphia says our ways of studying them have not changed much in 150 years.

Lacovara says he aims to change that. In his lab, he and James Tangorra, a mechanical engineer at Drexel, have been scanning dinosaur bones with lasers, hoping to apply the new technology of 3-D printing to these ancient specimens.

Three-dimensional printing, if you've never seen it, has nothing to do with images on paper. Instead, it involves the creation of an almost perfect model, made of layers of resin, of the scanned object. Lacovara and Tangorra have been working, for starters, on the humerus, or front leg bone, of a Cretaceous dinosaur called Paralititan stromeri, a giant four-legged plant-eating dinosaur found in what is now Egypt in 2000.

They are telling the computer to make a one-tenth-scale model of the fossil, to which they can attach artificial muscles and tendons. The original humerus (remember that since it's a fossil it's made of stone, not bone) weighs 800 lbs. The resin model weighs less than an ounce.

"In any science, the fewer assumptions you can make about your subject, the better," said Lacovara. In so much of paleontology, scientists have said, even the best conclusions about how dinosaurs lived and moved is based on guesswork - intelligent guesswork based on the shapes of the bones, but still something to be minimized.

For generations, to cite one famous example, scientists thought T. rex stood upright on its hind legs, dragging its tail behind it. Only in recent decades did they begin to think it may have balanced its tail in the air - and found the bones fit together much more neatly if it did.

In four or five months, Lacovara said he and and Tangorra hope to have a working model of Paralititan's front leg, articulated the way that makes the most sense when the resin models of the different bones are put together. In a year or two, they could perhaps have a complete skeleton, with which they could better figure out how it walked, ate and lived more than 65 million years ago.

"The next step is to robotocize these 3-D prints," said Lacovara. "We can study how the limbs moved with very few assumptions. We let the bones tell us their limits of movement - instead of us telling them what we think they should do."

Working with the models would be better than computer simulations of the dinosaur's motion, he said: "When you make a computer model, it's only as good as the assumptions you put in. When you have physical models, they're as good as the laws of the natural universe."

And one other thing: Three-dimensional printing is still fairly expensive, but as with many new technologies its cost is dropping quickly. So if scientists drop or break their model, all is not lost - they'll just tell their computer to print them a replacement.