Crowded with dinosaurs, petrified trees, and other prehistoric treasures, an ancient riverbed in Utah is surprising scientists. The discovery sheds new light on a Jurassic landscape dominated by dinosaur giants that lived 145 to 150 million years ago (prehistoric time line).
In just three weeks of work on federal land near Hanksville, Utah, paleontologists say they unearthed at least two meat-eating dinosaurs, a probable Stegosaurus, and four sauropods—long necked, long-tailed plant-eaters that could reach 130 feet (40 meters) long, making them the largest animals ever to have walked the Earth.
"So far [the paleontologists] have found not only scattered bones but partial and complete skeletons. It's really amazing," said Scott Foss, a paleontologist in the Bureau of Land Management's (BLM's) Salt Lake City office.
Big Sexy Dinosaurs
Some BLM employees and many locals had known that there were dinosaur bones to be found near Hanksville. But the recent dig led by scientists from the Burpee Museum of Natural History in Rockford, Illinois, was still a shocker.
"Nobody anticipated the scale or the scope of what was there. Once they started excavating, they realized that the magnitude was far more than they had expected," Foss said.
"About two weeks ago they notified us that this was pretty big and we'd better come and take a look."
The site, now known as the Hanksville-Burpee Quarry, is part of the Morrison formation. "[The formation is] where all the big sexy dinosaurs that we grew up learning about are most commonly found," Foss said.
Matthew Bonnan, of Western Illinois University, said, "In the late Jurassic you had the largest animals that ever walked the Earth.
"The sauropods sort of reached their zenith of size at this point," added Bonnan, who had just returned from the dig site.
Though the Hanksville-Burpee Quarry today is high and dry, it appears to have once been at a bend in a large, long-gone river.
A bar or other river feature likely collected the corpses of dinosaurs and other animals that died upstream and were washed down during high-water events over several centuries. The result is a logjam of fossilized bones.
The site's sandstone also encases freshwater clams, petrified trees, and other preserved matter. "There is potential that there could be burrows that contain fossil mammals. We have petrified logs—a whole group of things that I think are going to tell us something very detailed about this environment," Bonnan said.
(Related: "Ancient Mammal Relative Dug Burrows in Antarctica?" [June 9, 2008].)
The late Jurassic has been studied intensively for more than a century, yet some key questions linger.
"The big open question that remains is the environment in which the Morrison fauna and flora existed," said Hans-Dieter Sues, associate director for research and collections at the Smithsonian's National Museum of Natural History in Washington, D.C.
Sues has received funding from the National Geographic Society's Committee for Research and Exploration.
Early geologists imagined the Morrison-formation region as a vast swamp, the imagined prime real estate for all those sauropods.
"But later geologists argued that the Morrison was deposited in a dry environment with just some large bodies of water," said Sues, who is not involved with the Hanksville-Burpee dig.
New Look at Familiar Dinos?
Whatever mysteries the new site may hold, it is unlikely to produce any new dinosaur species, Sues said.
"Except for some really small dinosaurs—including possible bird relatives/precursors—or a good skeleton of the giant Brachiosaurus, there is going to be little that is newsworthy regarding Morrison dinosaurs," he said.
"The big discoveries to be made lie with other groups of Morrison animals, such as flying reptiles and mammals, which are still mostly known from very fragmentary remains."
But team member Bonnan hopes the Hanksville-Burpee will eventually rival Utah's other major Jurassic fossil troves—Dinosaur National Monument and the Cleveland-Lloyd Dinosaur Quarry.
"Even if we don't find anything new in terms of species, we're looking at old bones with new eyes and new technologies," he said.
"In the old days it was more about finding the 'biggest, baddest, bestest' dinosaurs, and a museum might have just cherry-picked those best specimens.
"Now there is more interest in the fossil assemblage—what does it tell you about the environment?"
The site will close for the season on Friday. But scientists are already anxiously awaiting the resumption of excavations next summer.
"It will take years to understand the real potential, or how big this site really is," BLM's Foss said. "But there is something there worth taking a really good look at."