A team of experts came to this conclusion after examining the bones of fish that perished on that fateful day when an asteroid measuring six miles in diameter impacted with the planet.
According to main author Melanie During, a doctoral student at Uppsala University in Sweden and lead author of an article published on Wednesday in the journal Nature, the fishes perished in the springtime. “The reign of the dinosaurs came to an end in the spring.”
Scientists have determined when the meteor struck — a little more than 66 million years ago, give or take 11,000 years — as well as where it struck, off the coast of Mexico’s Yucatán Peninsula. Although the Cretaceous period of Earth’s geological history came to an end as a result of the meteor, despite the fact that three-quarters or more of the world’s plant and animal species perished in the subsequent mass extinction, it has been difficult to find fossils of anything that was directly killed by the meteor.
However, in 2019, palaeontologists revealed the finding in southern North Dakota of what seemed to be a mass cemetery of species that perished within hours or days of the impact, which they believe was caused by a meteorite. Despite the fact that North Dakota was almost 2,000 miles away from where the meteor struck, the seismic waves from what was the equivalent of an earthquake with a magnitude of 10 or 11 sloshed water out of lakes and rivers, killing the fish in the process. Tektites, which are little glass beads thrown into the air by the collision, fell from the sky in a shower of tektites.
The location, known as Tanis, is located inside the fossil-rich Hell Creek formation, which runs over four states and was the subject of years of investigation by the researchers. Tanis was characterised as a “wonderland of fossil findings” in a storey published in The New Yorker; nevertheless, the first scientific report describing the site was relatively limited on specifics, focused instead on the geological environment.
Because of the new scientific findings, the fossils now reveal information about the disaster that was previously hard to decipher from the rocks.
A palaeontologist at the University of Edinburgh who was not involved in the research said it was “amazing” that they could pinpoint an event that occurred more than 66 million years ago, “literally a rock falling and striking the Earth in an instant.” “It’s amazing that we can take an event, a single moment that occurred more than 66 million years ago — literally a rock falling and instantly striking the Earth — and pinpoint that event to a specific time of year.” The narrative, in my opinion, is of the finest level of detective fiction.
Species in the Northern Hemisphere, some of which were emerging from hibernation or giving birth to young, may have been more susceptible to extinction than their southern counterparts.
In the Southern Hemisphere, animals hibernating in the fall months may have been better protected from the rapid, severe shift in temperature. According to Ms. During, “if you were able to hibernate, it would boost your odds.” Having the ability to lock oneself off in a tunnel or take refuge underwater might be quite advantageous to you.
Dr. Brusatte was in agreement. According to him, “I believe there is some promise here for assisting in understanding the patterns and processes of extinction.”
After seeing Jan Smit, a dinosaur specialist at Vrije University in Amsterdam, speak about Tanis, Ms. During became interested in the species. She began working on a master’s degree at the time and attended the discussion.
His account of the fossil discovery in North Dakota piqued her interest, and she wanted to know more. Then, from the back of the room, I began sending an email to him from my phone asking, ‘Hey, if you have these fishes, could we please conduct isotopic analysis on their bones?'” Ms. During made the statement.
She got in contact with Robert DePalma, the palaeontologist who was in charge of the Tanis project at the time. Ms. During travelled to North Dakota in August 2017 and spent ten days in Tanis digging up the fossils of six fish: three sturgeon and three paddlefish, among other species.
To prepare the bones for the study, the scientists chopped tiny sections of bone from the lower jaws of paddlefish and the pectoral fin spines of sturgeon in the laboratory. Like tree rings, they observed a pattern of recurrent bright and dark lines that represented seasonal variations in the rate of development. Observing the outermost section of the bones suggested that the fish were getting more active and developing at a quicker rate after the conclusion of the winter season.
The amount of plankton in the water for the fish to consume was determined by changes in the quantities of various forms of carbon in the bones, known as isotopes of carbon. The levels were lower than they would have been at the height of the summer’s abundance. Jeroen van der Lubbe, a paleoclimatologist at Vrije University in Amsterdam and one of the paper’s authors, said the finding contributed to the “many lines of evidence that we have indicating these fish died in the spring.”
They were discovered caught in the gills of the fish, but not in the digestive system, which was a surprise. “They weren’t able to swim on,” Ms. During said. “They perished very instantly.”
Another team of scientists headed by Mr. DePalma conducted a similar examination on fish fossils and came to almost the same results as Mr. DePalma’s team last December, which was published in the journal Scientific Reports.