A study reveals that the extinct dinosaurs arrived in the spring – 02/23/2022 – Science

celestial being that It came to Earth 66 million years agoand put an end to age of dinosaurs, arrived on our planet in the spring of the Northern Hemisphere, a new study reveals. The timing of the impact likely increased its devastating impact on species and ecosystems, affecting them at a delicate stage in their evolution.

The discovery, which came from careful investigation coordinated by European scientists, appeared in the scientific journal Nature, one of the world’s most important. “We are the first to conclusively show that the effect occurred in the spring, although work published since 1990 has already attempted to make this estimate,” he said. paper Dutch paleontologist Melanie Dhan, a doctoral student at Uppsala University in Sweden. During the new coordinated study, which was also signed by scientists from other European institutions.

The dull that caused the mass extinction crater formed Chicxuub, in the Yucatan Peninsula (Mexico). The rocks in the area have been scarred by the tsunamis caused by the impact, but the problem is that there are no fossils of animals directly killed by blows in these layers – or at least, no such fossils have been found so far. “This makes a study like ours not possible using this material,” explains During.

Therefore, the solution was to analyze the layers of rocks corresponding to the time of the collision located in the US state of North Dakota, approximately 3,000 kilometers from the Yucatan. Distance may seem useless, but it was already known that The Tanis fossil site, discovered in the area, contains a treasure: fish whose gills contain impact pellets, that is, small balls that are formed when a meteorite hits the Earth.

Therefore, the unlucky fish can serve as time capsules, because it bears geological imprints from the moment of impact (15 minutes to 30 minutes after the disaster, to be exact, according to scientists’ calculations). While he says he learned all this in 2017, when he listened to Professor Emeritus Jan Smit, of the Free University of Amsterdam, lecture about the North Dakota site. “And yes, the lecture was also given in the spring of that year,” he joked.

Speaking to Smit and her mentor at the time, Jeroen van der Loeb, I was able to travel to the United States that same year and began studying the fish associated with today’s sturgeon (the same ones whose eggs are the famous caviar). The animals were quickly buried when a phenomenon called “Seiche” (basically a tsunami in a confined body of water, with oscillating waves) struck the area shortly after the impact.

“I collected the jaw bones of the paddlefish and the pectoral fin spines of the sturgeon. I chose these bones because I found that they grow very similar to trees, adding a new layer each year. So we were curious to see if it would be possible to reconstruct the season in which they died.”

In flight: Analysis of the microscopic structure of the bone growth streaks showed that the fish died completely when a new growth streak began to form. This coincides with spring in the northern hemisphere, when food availability increases again after the lean cow stage of winter.

Another important clue is the chemical composition of bone. It is likely that fish feed on small crustaceans, and this is reflected in a periodic change in the presence in their bones of an isotope (variable) of the chemical element carbon, which is associated with the diet. This difference follows growth cycles, as expected.

says Brazilian paleontologist Rafael Delcourt, a postdoctoral researcher at the University of the South Pacific in Ribeirão Preto who commented on the study at the request of paper.

Another good idea, he said, was to study the fossils of fish that still had living relatives in the area and whose biology was well informed. “This gives some predictive power to understand how they grow, use resources, and deposit minerals in their skeleton.”

During and colleagues argue that the impact of spring would have been particularly severe for northern hemisphere species because the season would have coincided with the breeding season, when all resources are devoted to raising and caring for the young. Thus, many wild species, in addition to dealing with the immediate effects of the disaster, will still lose the next generation, even if they manage to survive.

In the southern hemisphere, where it was autumn, some animals would have already prepared for hibernation, remaining more protected in burrows (in the case of primitive mammals at that time). In fact, there are some indications that the Southern Hemisphere has first recovered from the tragedy. “Most of the research on this topic has been done in the Northern Hemisphere. I think this work is a catalyst for us to better understand the phenomenon in the Southern Hemisphere, and offers many ideas that can be applied, including to Brazilian fossils,” says Delcourt.