Scientists have long debated whether dinosaurs They 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 it’s just one piece of the global picture, independent experts say.
“The dinosaurs were quite diverse and now we know that there were quite different communities” wandering around before being abruptly eliminated, explained Daniel Peppeco-author of the study and a paleontologist at Baylor University.
The most recent evidence comes from analysis of a part of the Kirtland Formation in northern New Mexico, known for about 100 years to contain several interesting dinosaur fossils.
Scientists now say those fossils and surrounding rocks date back to about 400,000 years before the asteroid, which is considered a short interval in geological time. The age was determined by analyzing small particles of volcanic glass within the sandstone and studying the direction of magnetic minerals within the shale of the rock formation.
The results show that “the animals deposited here must have lived near the end of the Cretaceous”, the last era of the dinosaurs.said Peppe.
The findings were published Thursday in the journal Science.
The differences between the dinosaur species found in New Mexico and those previously found at a site in Montana and dated to the same period “contradict the idea that dinosaurs were in decline,” he said.
Fossils previously found at the New Mexico site include Tyrannosaurus rex, a massive, long-necked dinosaur, and a horned herbivore similar to Triceratops.
Scientists not involved in the study cautioned that evidence found in one place does not necessarily point to a broader trend.
“This new evidence about these dinosaurs surviving very late in New Mexico is very exciting,” said Mike Benton, a paleontologist at the University of Bristol who was not involved in the study. But he added: “This is just one place, not a representation of the complexity of dinosaur faunas at that time across North America or around the world.”
Although scientists have found dinosaur fossils on every continent, dating them accurately can be a challenge, said Andrew Flynn, a paleontologist and study co-author at New Mexico State University. Easily datable material like carbon does not survive in fossils, so scientists must look for surrounding rocks with precise features that can be used to determine ages.
Additional research could help complete the picture of what range of dinosaur species were alive globally on the eve of the asteroid impact, Flynn said.