Madrid 5 (European press)
“We determined the age of Utahraptor and found that it was much older than previously assumed,” Gregory Ludvigson, a scientist emeritus with the Kansas Geological Survey at the University of Kansas, who collaborated on the research, said in a statement. “This discovery has important implications for the evolutionary history of dinosaurs.”
The fieldwork was carried out in Utah at the famous Utahraptor Ridge site, named after the larger cousins of the ferocious dinosaur Velociraptor, one of the heroes of the Jurassic Park saga.
The ridge is home to Stikes Quarry, a quicksand deposit full of dinosaur fossils that have survived largely intact and preserved, in the same locations where they died. Stikes Quarry is part of the Cedar Mountain Formation, a unit of rock that contains fossils of more species of dinosaur than any other formation in the world.
“We also learned to our complete amazement that the rock strata in Stikes Dinosaur Quarry were deposited during an episode of global change known as the Weissert event,” said Ludvigsson. “This discovery set an agenda that will reverberate for decades.”
More than a decade ago, Ludvigson teamed up with Jim Kirkland, a state paleontologist with the Utah Geological Survey, and Matt Goeckel, a state geologist and director of the Department of Conservation Studies and Conservation at the University of Nebraska-Lincoln, to address this question.
The scientists and recruited colleagues adopted two research approaches: The first track, uranium/lead dating of zircon crystals, involves analyzing samples of these minerals collected at various depths in the rock layers. The second looked at changes in the relative abundances of two types of stable isotopes of carbon found in buried organic matter.
By comparing the results to periods in Earth’s history when global changes in the carbon cycle were known to occur, the team showed that the rocks in Gato Amarillo are a member of the Cedar Mountains Formation, and the Utahraptor fossils found in the interior, are older than 10 million years. Established. Previous estimates put the age of the rocks and fossils at 125 million years.
“This is a long evolutionary time,” Ludvigson said. “It’s kind of vindication of something Jim has been arguing for some time, but controversy never puts an age on it, and that’s important to him.”
The revised age indicates that the rocks in Stikes Quarry are at least 135 million years old. The Yellow Cat Member’s bottom includes older layers. The findings fill in a gap in the rock record at the boundary between the Jurassic and Cretaceous periods in Utah.
“Before, we had a gap of 25 million years between them, and that’s a third of the lifespan of mammals, more than twice the time of humans,” said Kirkland, who first named and described the dinosaur Utahraptor ostromaice in 1993. . development. It’s a lot of time. Anything could happen for 25 million years if you don’t have a record of what’s happening. We’ve plugged this record in, for the most part. “