Some of the latest dinosaurs were healthy and thriving right up until the day they were destroyed by the Armageddon asteroid, a new study of fossils from New Mexico has found.
Scientists debated for decades whether non-avian dinosaurs went into decline before a massive asteroid hit Mexico's Yucatan Peninsula late Cretaceous period (145–66 million years ago). A new study published Thursday (October 23) in the journal Scienceconfirms previous evidence that dinosaurs were struck in the prime of life And may still be roaming the Earth if it weren't for that pesky asteroid.
Researchers dated rocks from the Naashoibito Member fossil site in New Mexico, which preserved a rich Cretaceous ecosystem that was home to a variety of dinosaurs, including the 70-foot (21-meter) long-necked sauropod known as Alamosaurusas well as carnivorous tyrannosaurs, horned dinosaurs and duck-billed dinosaurs. Dating has shown that this ecosystem existed shortly before the Chicxulub asteroid impact, suggesting that New Mexico's last dinosaurs were living well before a giant space rock brought death from the sky.
“At least before the mass extinction, they seemed to be thriving,” says the study’s lead author. Andrew Flynnassistant professor of geological sciences at New Mexico State University, told Live Science via email. “The Nasxoibito area of New Mexico has a diverse dinosaur fauna, so the dinosaur population appears to be healthy.”
The asteroid caused mass extinction an event that caused the extinction of about 75% of living species, including all but dinosaurs birds. Previously, some studies had shown that dinosaur diversity had declined as a result of restructuring during the Maastrichtian period (72.1 to 66 million years ago) of the Cretaceous period, when environmental factors such as climate change made dinosaurs more vulnerable to disaster. However, other researchers argue that the asteroid interrupted the era of prosperity of the dinosaurs.
Most of what scientists know about the Cretaceous-Paleogene (K-Pg) boundary—the rocks that mark the end of the Cretaceous period—comes from formations such as Hell Creek and Fort Union in the northern U.S. Great Plains, which means there is a lot of uncertainty about what happened elsewhere.
Paleontologists knew that the Naashoibito member represented the last known non-avian dinosaurs of New Mexico, but the exact age of these fossils remains a matter of debate. In a new study, researchers tried to resolve this uncertainty by combining two stones. dating methods.
“We wanted to have two different, independent ways of determining the age of the rocks,” Flynn said.
The first of these methods involved measuring the radioactive decay of argon isotopes. The second one took advantage magnetic fields: Earth's magnetic field switches between a “normal” state where magnetic north is north (as it is now), and the reverse state where magnetic north is south. Researchers know when such upheavals occurred in Earth's history, so by measuring the direction of magnetic poles in rocks, they can determine their age.
Dating methods determined that the Naashoito member existed between approximately 66.4 and 66 million years ago, meaning dinosaurs lived there approximately 340,000 years after the asteroid impact. The researchers also found that New Mexico's dinosaurs were unique, suggesting that there were distinct pockets of dinosaur diversity in western North America.
“These revised estimates of dinosaur diversity during the Maastrichtian still do not match the richness of the previous Campanian period—the apparent zenith of dinosaur diversification in North America,” Lindsay Zanno– a paleontologist from North Carolina State University, who was not involved in the study, wrote in a cover letter. perspective published in the journal Science. “However, current estimates of Maastrichtian biodiversity are still higher than for most other Late Cretaceous periods.”
A new study paints a picture of the sudden extinction of dinosaurs due to an asteroid impact, leading to rapid growth of mammals soon after that. However, it is still unclear whether this was the case everywhere.
“This work really highlights the need to work on new, previously understudied sites during this incredibly important period in Earth's history,” Flynn said. “Just adding one new, well-dated dinosaur site in western North America allows us to see this really interesting picture of dinosaurs.”
