Before an asteroid wiped them out, dinosaurs were already in decline: study



Although the asteroid that struck the planet 66 million years ago wiped out the Earth non-avian dinosaurs, new research claims that environmental degradation groups of dinosaurs had started long before the historic event.

The Cretaceous-Tertiary extinction, arguably the most famous of all mass extinctions, wiped out 75% of living species on Earth.

However, a study published in the journal Nature Communications suggests that dinosaurs were in decline up to 10 million years before the Chicxulub, asteroid from Mexico.


“Our data indicate that the voluminous release of [nickel]-the rich gases triggered by the [Siberian Traps large igneous province (STLIP)] magmatism altered Upper Permian ocean chemistry long before the [end-Permian mass extinction (EPME)], ” the authors said.

EPME – also called the “Grand Mourant” – took place more than 251 million years ago, Kill more than 96% of marine species on the planet, 70% of terrestrial species and signaling the end of the Permian period.

In 2015, Earth and planetary science researchers from the Massachusetts Institute of Technology (MIT) reported in the journal Science Advances that massive volcanic activity in the Siberian traps occurred at the right time to have been a trigger for the most severe extinction event in the past 540 million years, calling the connection a ‘”inevitable”.

While it is not clear whether the explosive magmatism there was the primary trigger, the Nature study authors stated that “the destruction mechanisms of the event critically depend on the nature of the volatiles ejected. during STLIP eruptions “.

These destruction mechanisms – triggered 300,000 years earlier – include global warming, exposure to ultraviolet rays, hypercapnia, ocean acidification and anoxia, and the release of toxic metals, including the presence of isotopes of nickel.

“Our results provide strong evidence for the global dispersion and loading of Ni-rich aerosol particles into the Panthalasic Ocean,” the team wrote in the summary of the report.


the Panthalasic Ocean surrounded by the supercontinent of Pangea.

In a press release, CNRS and Fabien Condamine, a researcher at the Institute of Evolutionary Sciences in Montpellier (ISEM), said the team had examined evolutionary trends during the Cretaceous period for six major families of dinosaurs, including those of tyrannosaurs , triceratops and hadrosaurs.

Additionally, using a new statistical modeling method that “limits biases associated with gaps in the fossil record,” the group demonstrated that extinctions exceeded dinosaur speciations 76 million years ago.

“The impact of an asteroid 12 km wide 66 million years ago was therefore the final blow to a group of animals already in difficulty,” the statement said. “These results, published in Nature Communication on June 29, show that the disappearance of the dinosaurs was probably related to the global cooling towards the end of the Cretaceous, when the global average temperature dropped by [seven degrees Celsius.]”

Herbivores would have been particularly affected during the first extinctions, potentially “triggering cascading extinctions among other dinosaur families”.

Researchers looked at more than 1,600 dinosaur records during the Cretaceous Period, said Professor Phil Currie of the University of Edmonton. says Sci-News.


“It became clear that there were two main factors, first that the global climates were getting colder, and that made life more difficult for the dinosaurs who probably depended on the warm temperatures,” Mike Benton, co-author of study and paleontologist at the University of Bristol’s School of Earth Sciences, said in a declaration. “Then, the loss of herbivores made ecosystems unstable and prone to [an] extinction cascade. We also found that longer-lived dinosaur species were more susceptible to extinction, perhaps reflecting that they couldn’t adapt to the new conditions on Earth. “

Notably, not everyone agrees with their conclusions; others have published contradictory studies suggesting that the dinosaurs were still thriving when the asteroid struck.


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