Fossil hunters told: Dig deeper "Lots" more dinosaurs await discovery, experts say.

Posted: September 05, 2006

Dinosaur hunters of the world, grab your picks and hammers!

You've barely scratched the surface, according to a study published yesterday by scientists at the University of Pennsylvania and Swarthmore College.

A sophisticated statistical analysis suggests paleontologists have unearthed fewer than one-third of the various kinds of dinosaurs to be found, the team wrote in the online edition of Proceedings of the National Academy of Sciences.

"Good news for paleontology," said Steve Wang, an assistant professor of statistics at Swarthmore, who wrote the paper with Penn paleontologist Peter Dodson. "There's still lots out there to find."

A handful of such predictions have been made in the past. But since Dodson last did so in 1990, the rate of dinosaur finds has soared - the result of exploration in new areas and by new people. Once largely the province of white males from the United States, Britain and Canada, the field now encompasses many paleontologists from fossil hotbeds such as China and Argentina.

"It's no longer an imperialistic exercise," Dodson said.

And with the revelation that dinosaurs are ancestors of today's birds, paleontologists have vigorously pursued the smaller creatures that evoke their modern avian cousins.

"The emphasis has shifted from large dinosaurs that are going to add to the 'wow' factor of dinosaurs when mounted in museums," said Luis Chiappe, paleontologist at the Natural History Museum of Los Angeles County.

From the early 1800s until 1990, science had identified 285 dinosaur genera. (That's the plural of genus - a broader unit of classification than species, as in the "homo" in Homo sapiens.)

Then, in just the last quarter-century, the number climbed to 527, a jump of 85 percent. The total number of "recoverable" genera is 1,844, Dodson and Wang estimated. That doesn't count the likely hundreds of varieties that were not preserved in rock.

Michael Foote, a professor in the department of geophysical sciences at the University of Chicago, said the authors took a sound approach to the problem.

"I really like this paper," said Foote, who was not involved with the work. "I think this is, mathematically, a very rigorous attempt to deal with it."

Wang and Dodson used a statistical technique called an abundance-based coverage estimator - an analysis that took into account how many fossil finds throughout history represented new genera.

Loosely speaking, Wang said, that translates as follows:

"If you're always finding new things, you probably haven't found them all. . . . If you keep finding the same things over and over and over, that gives you an indication that you've probably found most things out there."

His calculations showed the reality to be somewhere in between.

He and Dodson projected that nearly 400 new varieties would be found in the next 30 years. The pace will likely level off during the 22d century, they wrote.

The authors also tackled a question related to dinosaur extinction. Fossils found to date suggest that dinosaur diversity was already in gradual decline 10 million years before the creatures' ultimate extinction, some experts say.

But Dodson and Wang's statistical method suggests that the population was stable, and that we simply haven't found their fossils yet.

That finding is consistent with the prevailing view that the creatures became extinct during a short period of time, as the result of a meteor impact at the end of the Cretaceous period.

Chiappe, who was not involved with the research, warned that such analysis must be viewed with some caution. If anything, he said, the new estimates might be too low.

Some parts of the world are relatively untapped when it comes to dinosaur fossils, notably Africa because of the turmoil in some countries, Chiappe said. But even traditional hunting grounds still have much to yield, he predicted.

Chiappe himself was part of a team that reported a new small dinosaur earlier this year, a 30-inch meat-eater from Germany dubbed Juravenator starki.

And if the new predictions hold true, there's plenty more to come.

"It's a safe bet," Dodson said, "that a child born today could expect a very fruitful career in dinosaur paleontology."

Contact staff writer Tom Avril at 215-854-2430 or tavril@phillynews.com.

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