“It was a real reset button”: in the transition of the geological periods called Eocene and Oligocene, almost two-thirds of the known species in Europe and Asia would have become extinct.
About 30 million years ago Africa and the Arabian Peninsula suffered a mass extinction in which 63% of mammal species were lost, but that until now had not been documented, according to a study published by Communications Biology.
That extinction occurred in the transition of geological periods called Eocene and Oligocene, which cooled the earth’s climate.
Although it was known that had affected mammal species in Europe and AsiaIt was believed that Africa could have escaped unscathed as its milder climate would have been a buffer against the worst of the cooling trend of that period, but it was not.
A team of researchers has come to this conclusion analyzing a vast collection of hundreds of fossils from various places on that continent.
Two-thirds of the species in Europe and Asia became extinct
That period was marked by a drastic climate change in reverse of what happens today. The Earth cooled, the ice sheets expanded, the sea level dropped, the forests began to turn into meadows and carbon dioxide was in short supply.
Almost two thirds of the known species in Europe and Asia have become extinct, indicates Duke University (United States), one of the signatories of the study.
The experts examined the fossils of five groups of mammals: one of extinct carnivores called hyaenodontes; two from rodents, including squirrels and porcupines; two others from primates, strepsirrhines (lemurs and lorises), and anthropoids (apes and monkeys).
Evolutionary trees from the study of fossils
By studying the fossils, they were able to create evolutionary trees, noting when new lineages branched out and marking the time of the earliest and last known appearances of each species.
The results show that the five groups of mammals studied suffered “huge” losses around the Eocene-Oligocene boundary.
“It was a real reset button”according to study lead author Dorien de Vries of the University of Salford (UK).
After a few million years, these groups reappeared in the fossil record, but with a new appearance, that is, the fossil species of the Oligocene, after the great extinction event, are not the same as they were before.
Molar teeth tests
The proof is in the molar teeth of these animals, which can tell a lot about what a mammal eats and, therefore, its environment.
The rodents and primates that reappeared after a few million years they had different teeth. They were new species, eating different things and having different habitats.
“We see a huge loss of tooth diversity, and then a recovery period with new tooth shapes and new adaptations.”said de Vries.
Rapid climate change was not the only challenge faced by those few surviving types of mammals. East Africa was also hit by a series of major geological events.
During that period, volcanic supereruptions occurred that covered vast expanses with molten rock and that was when the Arabian Peninsula separated from East Africa, opening up the Red Sea and the Gulf of Aden.