According to many sources, about 50 million years ago, an ancient continent called Balkanadolu (Balkanatolia) sat between Europe and Asia and was home to a number of interesting species unlike those found in neighboring landmasses. The authors of a new study suggesting the existence of this continent suggest that falling sea levels have allowed Asian mammals to enter the Balkanadolu and take their place, defeating local wildlife before crossing into Western Europe and a sudden extinction event.
Known as the Grande Coupure, this dramatic loss of European fauna occurred at the end of the Eocene epoch, about 34 million years ago. However, the study authors, who present their research in the journal Earth-Science Reviews, explain that Asian species began appearing in the fossil record in Southeast Europe about five to ten million years ago.
To fill in the gaps in the timeline to the Grande Coupure, the researchers reviewed all 31 Eocene mammalian fossil records from the Balkan peninsula and Anatolia and reassessed the history of some of these finds based on updated geological data. Their results showed that for most of the era, the region existed as “a previously unrecognized biogeographical region here called Balkanadolu”.
However, the fossil record also showed that Asian rodents and four-legged ungulates colonized the region about 40 million years ago. Among the Asian species that invaded Balkanadolu before the end of the Eocene were brontotheres, which resembled the great rhinoceros but became extinct by the time of the Grande Coupure.
“This colonization event was facilitated in the late middle Eocene by a drop in global eustatic sea level and a tectonic-driven sea retreat in eastern Anatolia and the Lesser Caucasus,” the study authors write.
Until 34 million years ago, when a glaciation event caused sea levels to drop once again, Balkanadolu was connected to Western Europe by a land bridge. This paved the way for Asian mammals to continue their westward journey and triggered the death of many European species.
In other words, the researchers suggest that major geographic changes between 40 and 34 million years ago enabled Asian ungulates and rodents to colonize Europe in two stages. In the first of these, they resided in Balkanadolu, where they replaced much of the wildlife available before continuing to later conquer the European continent.
“These paleogeographic changes triggered the demise of Balkanadolu as a distinct biogeographic region and paved the way for the dispersal of endemic branches to Asia before and during the Grande Coupure in Western Europe,” the authors write.
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