According to scientists from New Mexico State University, they were dinosaurs at the peak of development until the very impact of the asteroid that triggered their mass extinction. In doing so, they question the long-standing theory that dinosaurs were already declining before the impact of the asteroid. According to the authors, on the contrary, these creatures were in full bloom until the moment when their sixty-six million years ago, a catastrophe struck, causing their total annihilation.
“I think we can say based on our new study that, at least in North America, dinosaurs were not headed for extinction,” said the doctor Andrew Flynnlead author of the research from New Mexico State University.
The authors of a study published in the journal Science used a new method to date the Naashoibito Member rock layer in the San Juan Basin in New Mexico. They used two methods – analysis of the ratio of two argon isotopes in rock crystals and analysis of the orientation of magnetic particleswhich preserve the direction of the Earth’s magnetic field at the time the rock was deposited.
“The extinction event itself happened essentially right in the middle of a relatively short period when the Earth’s magnetic poles were reversed,” Flynn said. The results of the analysis show that the part of the rock in which the youngest known dinosaur fossils are found in the southern part of North America was formed at most 350,000 years before the asteroid impact. “These are the very last dinosaurs in southern North America,” dodal Flynn.
Scientists have also found that the dinosaurs of that time were more diverse than previously thought. “In the north there were many horned triceratops and classic duck-billed dinosaurs like Edmontosaurus. But in the south there were duck-billed dinosaurs with prominent crests and, most interestingly, giant sauropods.” There are no signs that these dinosaurs were in trouble, that anything unusual was going on with them, or that they were in any kind of long-term decline.” added research co-author Professor Steve Brusatte from the University of Edinburgh.
Flynn added that the apparent decline in dinosaur diversity before the asteroid impact may just be the result of less exposed rock from the end of the Cretaceousand thus a smaller number of found fossils.
