Imagine the scene. It was a quiet afternoon in the Cretaceous world, dinosaurs roamed the planet freely and the Mesozoic era seemed to be in its heyday. But suddenly, about 66 million years ago, a gigantic asteroid of more than 10 kilometers in diameter crashed into what we now know as the Yucatan Peninsula, in Mexico, and triggered the mass extinction that would end with three quarters of all species on the planet. Including the majestic and iconic dinosaurs. So far, the story that we all more or less know. But this Wednesday a new study published in the journal ‘Nature’ It provides one more piece of information to finish framing the moment. The extinction of the dinosaurs began in the spring of the northern hemisphere. Or in the fall of the southern hemisphere, depending on how you look at it.
The investigationled by a team from Uppsala University in Sweden, sheds light on a turning point in the history of life on Earth. Until now, the great extinction of the dinosaurs had been analyzed on a millennial time scale. In other words, the rivers of ink that have flowed over this key episode in the history of life on the planet tell what happened in the thousands of years after the impact. The recently presented study, on the other hand, manages to do ‘zoom’ in the timeline and, for the first time, pinpoints the exact season in which the asteroid collided that put an end to the age of the dinosaurs.
To resolve this prehistoric mystery, the study analyzes a set of fossil remains of sturgeons and paddlefish found in a site in North Dakota (in the United States) that, as if it were a time machine, show a snapshot of what the world was like during the Upper Cretaceous. According to the team of researchers that has led this work, scrutiny of these fossils first revealed that the fish died almost instantly after the asteroid impact. The animals had remains of the impact on their gills, so everything indicates that they died “immediately” due to the sudden waves that the asteroid caused in continental waters.
The second great conclusion, which is the one that grabs headlines around the world, is the “definitive proof” that the asteroid that killed the dinosaurs hit Earth during the northern hemisphere spring. The fossil records analyzed in this study, in fact, show a large presence of fish in the deposit. Many of them, in different stages of the life cycle. This, according to the experts who have led this work, suggests that the great impact coincided with the reproductive season of these specieswhich just happens in spring.
jurassic spring
Know that the beginning of the end of the dinosaurs started during the spring goes far beyond a simple anecdote. “It’s not just a curious fact, it’s a unpublished information to understand how this mass extinction of species occurred, one of the largest ever experienced on the planet”, comments the paleontologist and science communicator Francesc Gascó, author of ‘This was not in my dinosaur history book’ (Gualdamazán, 2021). “Discover in which season the great impact occurred from the study of a fossil record is especially interesting. Especially since it opens the door to apply this technique to the study of other historical moments to refine its dating even more”, adds the expert, independent to the ‘Nature’ study this Wednesday, in statements to EL PERIÓDICO.
speaking of the season when the dinosaurs became extinct, Gascó explains that the spring then and now do not have much to do. “The average temperature of the planet was higher than now“, clarifies the paleontologist, who also works as a teacher at the Isabel I University and a member of the Spanish Society of Paleontology. “At a landscape level, the world began to resemble what we have now, but still not quite the same“, he adds. On the planet of the dinosaurs, for example, the world map was different from the current one. There were plants and there were flowers, yes. But not as many or as colorful as now. According to Gascó, in fact, the explosion of flowering plants occurs right during the decline of the dinosaurs.
the autumnal south
The ‘Nature’ study also outlines what happened in the southern hemisphere after the asteroid’s collision. To begin with, the research concludes that the decline of dinosaurs in the global south began in the fall. Everything indicates that, after the impact of the asteroid, the ecosystems of the southern hemisphere recovered twice as fast as their counterparts in the north. In part, because the collision coincided with a period when many species were hibernating. Likewise, the study indicates, it is possible that the wave of fires that hit the southern hemisphere at that time had already led many animals to flee or take refuge in burrows.
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In general terms, according to the authors of this new research, the brutal collision of the asteroid triggered “a collapse of ecological networks from the bottom up“. The first victims of the impact were the animals that died instantly. Then the tsunami of dust, ash and steam that inundated the planet was fattened with the plants. With the flora decimated, the species dependent on the vegetation also perished. And the predators of the latter also suffered from the loss of food. asteroid changed life on earth and ended the reign of the dinosaurs. And now, to complete the story, we know that all this happened just when prehistoric flowers were at their peak.
The rise of the dinosaurs
The age of the dinosaurs ended more than 66 million years ago. But that does not mean that, thanks to the tireless work of the scientific community, we are currently facing a veritable ‘resurgence’ of the dinosaurs. In recent years, without going any further, EL PERIÓDICO has explained several surprising discoveries of dinosaurs. Many of them, in Spain itself. In the midst of a pandemic, for example, it was discovered that a fossil that had been kept in a home for more than twenty years was, in fact, a dinosaur that inaugurated a new genus and a new species; the ‘Portellsaurus sosbaynati’, discovered neither more nor less than in Portell de la Morella, Castellón. Another of the most surprising findings of recent times is, without a doubt, the discovery of a new species of dinosaur that lived in the Pyrenees 70 million years ago. The animal, whose remains also survived several decades of oblivion, measured 18 meters and weighed 14 tons. His remains can be visited, shortly, in the Museum of the Conca Dellà, in Lleida.