Cutting-edge quantitative analysis of the mass extinction that occurred 215 million years ago reveals it was not linked to any single catastrophic event, scientists have discovered. Extinction experts now believe the Triassic-Jurassic apocalypse event did not occur suddenly or simultaneously.
This shocking conclusion is the disappearance of a wide variety of species was not the consequence of either asteroid impacts or climate change.
We concluded that neither the asteroid impact nor the climate change had anything to do with the extinction
Professor David Fastovsky
The University of Rhode Island (URI) research was based on paleontological field work performed on sediments 227 to 205 million years old in Arizona’s Petrified Forest National Park.
Geoscientists have long suspected the disappearance of the Adamanian/Revueltian turnover had never previously been reconstructed satisfactorily.
Some researchers believed the extinction was triggered by the Manicouagan Impact, an asteroid impact that occurred in Quebec 215.5 million years ago, leaving a distinctive 750-square-mile lake.
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Others speculated the extinction was linked to a hotter and drier climate occurred at approximately the same time.
URI’s Professor David Fastovsky believes the extension occurred in a wide area and was “drawn-out”.
He said: “Previous hypotheses seemed very nebulous, because nobody had ever approached this problem—or any ancient mass extinction problem—in the quantitative way that we did.
“In the end, we concluded that neither the asteroid impact nor the climate change had anything to do with the extinction, and that the extinction was certainly not as it had been described—abrupt and synchronous.
“In fact, it was diachronous and drawn-out.”
The Adamanian/Revueltian turnover is considered perfect candidate for applying the quantitative methods for the landmark research.
This is because the fossil-rich layers at park preserve a diversity of vertebrates from the period.
These include ancient animals including the crocodile-like phytosaurs, armoured aetosaurs, early dinosaurs, large crocodile-like amphibians and other land-dwelling vertebrates,
Student, Reilly Hayes who led the study, relocated the sites where known fossils were discovered and precisely determined their age by their position in the rock sequence.
Ms Hayes and URI Statistics Professor Gavino Puggioni proceeded to apply several complex statistical algorithms to create “a probabilistic estimate” when the animals likely died out.
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This “Bayesian” method allowed for an unusually precise assessment of the likelihood that the Adamanian vertebrates in the ancient ecosystem went extinct dramatically and synchronously, as would be expected with an asteroid impact.
Previous research concluded the asteroid impact occurred 215.5 million years ago and the consequential climate change between three to five million years later.
The researchers demonstrated the extinctions happened over an extended period between 222 million years ago and 212 million years ago.
Some species of armoured archosaurs Typothorax and Paratypothorax, for instance, went extinct approximately six million years before the impact and 10 million years prior to the climate change.
The Acaenasuchus, Trilophosaurus and Calyptosuchus went extinct two to three million years before the impact.
Desmatosuchus and Smilosuchus species, on the other hand, died out two to three million years after the impact and during the very early stages of the climate change.
Professor Fastovsky added: “It was a long-lasting suite of extinctions that didn’t really occur at the same time as the impact or the climate change or anything else.
“No known instantaneous event occurred at the same time as the extinctions and thus might have caused them.”
The URI professor believes it will be difficult to apply these quantitative methods to calculate other mass extinctions because equally rich fossil data and precise radiometric dates are unavailable at other sites and time periods.
He said: “This was like a test case, a perfect system for applying these techniques because you had to have enough fossils and sufficiently numerous and precise dates for them.
“Other extinctions could potentially be studied in a similar way, but logistically it’s a tall mountain to climb.
“It’s possible there could be other ways to get at it, but it’s very time consuming and difficult.”
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