Dinosaurs thriving in North America before mass-extinction asteroid strike: Study
Scientists have long wondered whether dinosaurs were in decline before an asteroid hit Earth 66 million years ago, causing a mass extinction.
New research suggests dinosaur populations were still thriving in North America before the asteroid impact, but that’s only part of the global picture, independent experts say.
“Dinosaurs were very diverse, and we now know that there were quite distinct communities” that roamed around before being abruptly wiped out, said Daniel Peppe, a study co-author and paleontologist at Baylor University.
The latest evidence comes from analysis of part of the Kirtland Formation in northern New Mexico, known for about 100 years to contain several interesting dinosaur fossils.
Scientists now say that these fossils and surrounding rocks date from about 400,000 years before the asteroid impact, which is considered a short geological time interval. The age was determined by analyzing small particles of volcanic glass in the sandstone and studying the direction of magnetic minerals in the mudstone of the rock formation.
The results show that “the animals deposited here must have lived toward the end of the Cretaceous,” the last era of dinosaurs, Peppe said.
The results were published Thursday in the journal Science.
The differences between the dinosaur species found in New Mexico and those found at a site in Montana that previously dated to the same time period “run counter to the idea that dinosaurs were in decline,” he said.
Previously discovered fossils at the New Mexico site include Tyrannosaurus rex, a huge, long-necked dinosaur, and a horned herbivore resembling a Triceratops.
Scientists who were not involved in the study cautioned that evidence found in one location might not indicate a broader trend.
“This new evidence about these dinosaurs surviving very late in New Mexico is very interesting,” said Mike Benton, a paleontologist at the University of Bristol, who was not involved in the study. But he added: “It’s just one location, not a representation of the complexity of dinosaur faunas at the time throughout North America or around the world.” »
Although scientists have found dinosaur fossils on every continent, precisely dating them can be a challenge, said paleontologist and study co-author Andrew Flynn of New Mexico State University. Easily datable materials such as carbon do not survive in fossils. Scientists therefore need to look for surrounding rocks with specific characteristics that can be used to determine ages.
Further research could help complete the picture of the range of dinosaur species alive in the world on the eve of the asteroid crash, Flynn said.
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