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New research indicates that dinosaur populations in North America were thriving just before an asteroid impact 66 million years ago caused their mass extinction.
The discovery offers a new perspective on a long-standing scientific debate over whether their numbers were already in decline. However, experts caution that this represents only one piece of the global ecological puzzle.
,dinosaur were quite diverse and now we know there were different communities” that were moving around before suddenly being wiped out, said study co-author Daniel Peppe, a paleontologist at Baylor University.
The latest evidence comes from analyzing a portion of the Kirtland Formation in northern new mexico It has been known for many interesting dinosaur fossils for almost 100 years.
Scientists now say those fossils and surrounding rocks date back to about 400,000 years before the asteroid hit, which is thought to be a short interval in geologic time. The age was determined by analyzing small particles of volcanic glass within the sandstone and studying the direction of magnetic minerals in the mudstones of the rock formation.
The results suggest that “the animals deposited here may have been living near the end of the Cretaceous”, the last dinosaur era, Mr Peppe said.
The findings were published Thursday in the journal Science,
The differences between dinosaur species found in New Mexico and dinosaur species found at a site in Montana previously dated to the same time frame, “contrary to the idea that dinosaurs were in decline,” he said.
Previously found fossils at the New Mexico site include Tyrannosaurus rex, a huge, long-necked dinosaur, and Triceratops, a horned herbivore.
Scientists who were not involved in the study cautioned that evidence from one location may not point to broader trends.
“This new evidence about these very late-lived dinosaurs in New Mexico is very exciting,” said paleontologist Mike Benton of the University of Bristol, who was not involved in the study.
However, he added that it was “just a location”. It was “not representative of the complexity of the dinosaur fauna in all of North America or the world at that time”.
Although scientists have found dinosaur fossils on every continent, accurately dating them has been a challenge, said Andrew Flynn, a paleontologist at New Mexico State University and co-author of the study.
Easily datable materials like carbon do not survive in fossils, so researchers must look for nearby rocks with precise characteristics that can be used to determine the age.
Mr Flynn said further research could help paleontologists find out what types of dinosaur species were alive globally on the eve of the asteroid crash.