The dinosaurs were not in decline when an asteroid crashed on the earth and suffered them, say the scientists. Instead, the idea that the diversity of dinosaurs decreased before asteroids hit 66 million years ago is probably based on defective fossil data, according to a study that has examined almost 18 million years of fossil evidence.
Fossil discoveries have long indicated that dinosaurs were Retaining in number and diversity Before the impact of asteroids at the end of Cretaceous. Previously, some researchers thought it was a sign that dinosaurs were already on the road to extinction even before the cataclysmic meeting with a space rock. However, this idea has long been controversial, other researchers arguing that The diversity of dinosaurs was going very well at the time of their disappearance.
“It’s a subject of debate for more than 30 years – were the dinosaurs condemned and already by leaving before the asteroid blow?” Principal author of the study Chris DeanA paleontologist told the University College in London, in a statement.
Now new research published Tuesday April 8 in the journal Current biology suggests that the apparent scarcity of dinosaurs before their extinction can simply be due to a bad fossil file.
Scientists have studied recordings of approximately 8,000 Fossils from North America dating from the Campanian Age (83.6 million to 72.1 million years) and the Maastrichtian Age (72.1 million to 66 million years), focusing on four families: Ankylosaudae, Ceratopsidae, Hadrosaudae and Tyrannosaura.
At its nominal value, their analysis showed that the diversity of dinosaurs culminated about 76 million years ago, then decreased until the strike of asteroids destroys non -avian dinosaurs. This trend was even more pronounced during the 6 million years before mass extinction, the number of fossils of the four families decreasing in the geological file.
However, there is no indication of environmental conditions or other factors that would explain this decline, revealed the researchers. All the families of dinosaurs were widespread and common, according to models developed by researchers – and therefore at low risk of extinction, with the exception of a catastrophic event such as the impact of asteroids.
The Maastrichtian can rather have lower geological conditions for fossilization, have suggested the researchers. Events such as the retirement of the Western interior maritime route, which once went from the Gulf of Mexico across the Arctic, and the rise of the rocky mountains starting around 75 million years agoMay have hampered or disrupted fossilization, which gives the impression that there was fewer dinosaurs and less diversity during this period.
The team also found that the geological outcrops of the Maastrichtian of North America were not exposed or were covered by the vegetation. In other words, rock of that time which could contain fossils of dinosaurs was not easily accessible to researchers who were looking for the remains. Since half of the known fossils of this period come from North America, the results of the study can also have global implications.
Among the 8,000 fossil files examined, the team found that the Ceratopsians – a group which includes horns in horns like Triceratops And his parents – were the most common, probably because they lived in the simple regions which were most conducive to conservation during the Maastrichtian. Hadrosaurians – Duck beak dinosaurs – were the least common, perhaps because of their preference for rivers. Reductions for the flow of rivers may have led to less sediment deposits that could have preserved these dinosaurs, researchers wrote in the study.
“Dinosaurs were probably not inevitably doomed to extinction at the end of the mesozoic (252 million at 66 million years)”, co-author of the study Alfio Alessandro ChiarenzaA paleontologist told the University College in London, in a statement. “If it was not for this asteroid, they could always share this planet with mammals, lizards and their surviving descendants: birds.”
Publisher’s note: This article was published for the first time on April 8, 2025.