Alamosaurus was one of the final dinosaurs to live in the southern part of North America when the space rock impacted.
According to a recent study on fossils discovered in New Mexico, several of Earth’s last dinosaurs were robust and flourishing just before they were wiped out by an asteroid-induced cataclysm.
For several decades, experts have questioned whether non-avian dinosaurs were diminishing in numbers before a huge asteroid collided with Mexico’s Yucatán Peninsula towards the close of the Cretaceous period (145 million to 66 million years ago). The latest research, released on Thursday (Oct. 23) in the journal Science, backs up prior data indicating that the dinosaurs were terminated at their peak and might have still wandered the planet if not for that troublesome asteroid.
Scientists determined the age of rocks from the Naashoibito Member fossil location in New Mexico, which held a diverse Cretaceous ecosystem teeming with different dinosaurs, such as the 70-foot-long (21 meters) long-necked sauropod known as Alamosaurus, in addition to carnivorous tyrannosaurs, armored dinosaurs, and hadrosaurs. The dating process demonstrated that this ecosystem was present shortly before the Chicxulub asteroid impact, implying that New Mexico’s remaining dinosaurs were thriving before the enormous space rock caused annihilation from above.
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According to study leader Andrew Flynn, an assistant professor in the Department of Geological Sciences at New Mexico State University, “They seemed to be prospering, at least before the mass dying,” as expressed to Live Science via email. “The dinosaur fauna in the Nasshoibito Member in New Mexico is diverse, indicating a robust dinosaur population.”
The asteroid initiated a large-scale extinction event that eliminated around 75% of all living species, including all dinosaurs, with the exception of avian species. Prior research has suggested that dinosaur variety decreased during a reorganization in the Maastrichtian era (72.1 million to 66 million years ago) of the Cretaceous, when ecological variables like shifts in the climate rendered dinosaurs more susceptible to calamities. On the other hand, other scientists have claimed that the asteroid put an end to a time of affluence for dinosaurs.
The majority of what experts understand about the Cretaceous-Paleogene (K-Pg) boundary — the geological layers that signify the culmination of the Cretaceous period — has originated from formations like Hell Creek and Fort Union located in the northern Great Plains of the U.S., creating significant uncertainty concerning events elsewhere.
Paleontologists were aware that the Naashoibito Member encompassed New Mexico’s last identified non-avian dinosaurs; however, the exact age of these fossils remained a subject of contention. In the current research, scientists aimed to address this ambiguity by utilizing a combination of two methods for dating rocks.
“We desired to attain two differing, separate methods for ascertaining the age of the rocks,” noted Flynn.
Scientists gather paleomagnetic specimens in the San Juan Basin of northwestern New Mexico.
The initial approach involved calculating radioactive deterioration in argon isotopes. The second method utilized magnetic fields: The planet’s magnetic field switches between a “normal” state, where magnetic north corresponds to north (as it does currently), and an inverted state, where magnetic north is located south. Scientists possess knowledge regarding the timing of these switches throughout the history of Earth; therefore, they can determine the age of rocks by evaluating the direction of magnetic poles.
The dating processes positioned the Naashoibito Member approximately between 66.4 million and 66 million years in the past — signifying that the dinosaurs there existed in proximity to the asteroid strike, within roughly 340,000 years. Furthermore, the scientists discovered that New Mexico’s dinosaurs displayed distinct characteristics, implying the presence of unique zones of dinosaur variation in western North America.
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Lindsay Zanno, a paleontologist from North Carolina State University who wasn’t involved in the study, penned an accompanying viewpoint released in Science, stating that “These amended evaluations concerning dinosaur diversity during the Maastrichtian phase still do not correspond to the wealth of the preceding Campanian Epoch — the observable apex of dinosaur diversification within North America. “Nevertheless, present estimations of Maastrichtian biodiversity remain elevated compared to the majority of other Late Cretaceous epochs.”
The recent study depicts an abrupt termination of dinosaurs due to the asteroid impact, which resulted in the swift proliferation of mammals shortly thereafter. It remains uncertain, though, whether this phenomenon was universally observed.
“This research truly underscores the necessity to examine fresh, previously overlooked locations existing during this remarkably pivotal juncture in the Earth’s past,” expressed Flynn. “Simply incorporating a single novel, well-dated dinosaur-bearing site situated in western North America enables us to discern this genuinely intriguing depiction of dinosaurs.”
Patrick PesterSocial Links NavigationTrending News Writer
Patrick Pester holds the position of trending news writer for Live Science. His articles have been featured on additional scientific platforms, including BBC Science Focus and Scientific American. Following his prior experience in zoos and wildlife conservation, Patrick underwent retraining to become a journalist. Upon being granted the Master’s Excellence Scholarship for studies at Cardiff University, he successfully finished a master’s program in international journalism. Furthermore, he possesses a second master’s degree in biodiversity, evolution, and conservation in action attained from Middlesex University London. Beyond his role as a news writer, Patrick investigates the trade of human remains.
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