Friday, July 20, 2007


Jul. 20, 2007 (McClatchy-Tribune Regional News delivered by Newstex) --
Paleontologists working at Ghost Ranch are rewriting the history of the dinosaur. It seems dinosaurs were not the fast-rising evolutionary power brokers that some scientists have thought, according to new fossils found in the red rock country of northern New Mexico.

Discoveries, made last year and described today in the journal Science, suggest a gradual rise by the creatures that came to dominate their world for more than 150 million years.

Some scientists have argued that dinosaurs came on with a bang during the period of Earth history called the Triassic, sweeping into power in what amounted to a geologic instant.

But the new fossils, found at Ghost Ranch near Abiquiu, upend that story. As dinosaurs were beginning their rise to power, other dinosaurlike creatures lived with them side by side for 15 million to 20 million years, the newfound fossils suggest.

Among them were the bones of a newly discovered dinosaurlike creature scientists named Dromomeron romeri.

'They're coexisting with true dinosaurs,' said Randall Irmis, the Berkeley graduate student who led the study.

The dinosaurs and Dromomeron were closely related but from different branches of the evolutionary tree -- like the difference between chimpanzees and humans, explained Sterling Nesbitt, one of the paper's coauthors.

The notion of the rapid rise of the dinosaurs has been on shaky ground for some time, and Irmis and his colleagues 'provide a biological nail in the coffin' to the idea, said Andy Heckert, a dinosaur expert at Appalachian State University in North Carolina.

The work also demonstrates the importance of New Mexico's fossil beds to understanding the dawn of the dinosaurs, according to Heckert, who has worked in the area for years.

The region around Abiquiu and Ghost Ranch, 50 miles northwest of Santa Fe, has a storied history in the annals of dinosaur hunting, begun with the famed paleontologist Edward Drinker Cope in the 19th century.

It was 120 years ago that Cope named what is now the New Mexico state fossil, a small meat-eater called Coelophysis. Then, in the 1940s, a team from the American Museum of Natural History found a trove of dinosaurs in a fossil quarry at Ghost Ranch.

In recent years, a younger generation of fossil hunters, people like Heckert and Irmis, have placed the area back in the dinosaur spotlight.

In 1998, Heckert began digging at Snyder Quarry, a dinosaur fossil site named after its discoverer, California firefighter and dinosaur enthusiast Mark Snyder.

Then, in 2002, amateur archaeologist John Hayden found what came to be known as the Hayden Quarry, where Irmis and his colleagues made their big find.

Preliminary excavations by Ghost Ranch paleontologist Alex Downs yielded a modest haul of bones of dinosaurs and dinosaurlike creatures. When Irmis and Nesbitt saw them during a 2005 visit, it was immediately obvious what they had.

'We knew right away,' said Nesbitt, of the American Museum of Natural History in New York.

Just six months before, Irmis, Nesbitt and a group of colleagues had begun a project to review all the fossils they could find from that era in history in hopes of sorting out what happened at the dawn of the dinosaur era.

After seeing Downs' Hayden Quarry fossils, they returned for a major dig in spring 2006.

The emergence of dinosaurs is an example of evolution in action. In the end, it was a zero sum game, as dinosaurs squeezed out other similar animals, out-competing them to dominate both large planteating and meat-eating niches.

Among those left by the wayside was Dromomeron.

By the beginning of a period of Earth history known as the Jurassic, about 200 million years ago, dinosaurs were dominant. The evolutionary question is how quickly they rose to that dominance.

One theory had the dinosaurs rising quickly, about 225 million years ago, perhaps taking advantage of a mass extinction event that had cleared out the competition. That is the path mammals took to dominate the modern world.

Not so the dinosaurs, whose coexistence with Dromomeron and its kin suggest a different path to power.

Newstex ID: KRTB-0010-18293557


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