A low-lying continent that existed around 40 million years ago and was home to exotic fauna may have “paved the way” for Asian mammals to colonise southern Europe, according to new research.
Sandwiched between Europe, Africa and Asia, the forgotten continent — which researchers have dubbed “Balkanatolia” — became a gateway between Asia and Europe when sea levels dropped and a land bridge formed around 34 million years ago.
“When and how the first wave of Asian mammals arrived in southeastern Europe remains poorly understood,” write paleogeologist Alexis Licht and his colleagues in their new study.
But the result was simply dramatic. About 34 million years ago, at the end of the Eocene epoch, large numbers of native mammals disappeared from western Europe with the emergence of new Asian mammals, in a sudden extinction now known as the Great Divide.
However, recent fossil discoveries in the Balkans have turned this timeline on its head, pointing to a ‘special’ bioregion that appears to have allowed Asian mammals to colonise south-eastern Europe up to 5–10 million years before the Great Divide.
To investigate, Licht, of the French National Centre for Scientific Research, and his colleagues re-examined the evidence from all known fossil sites in the region, which covers the present-day Balkan Peninsula and Anatolia, the westernmost projection of Asia.
The ages of these sites were revised on the basis of current geological data, and the team reconstructed the palaeogeographical changes that occurred in the region, which has a “complex history of episodic drowning and re-emergence”.
What they found suggests that Balkanatolia served as a springboard for animals to move from Asia to western Europe, with the transformation of the ancient landmass from a self-sustaining continent to a land bridge — and the subsequent invasion by Asian mammals — coinciding with “dramatic palaeogeographic changes”.
About 50 million years ago, the Balkans were an isolated archipelago, separated from neighbouring continents, where a unique collection of animals distinct from those of Europe and East Asia flourished, the analysis says.
Then, a combination of sea level fall, Antarctic ice sheet growth and tectonic changes linked the Balkanatolian continent to western Europe between 40 and 34 million years ago.
This allowed Asian mammals, including rodents and four-legged hoofed mammals (aka ungulates), to venture westward and invade the Balkans, according to the fossil record.
In addition to this record, Licht and his colleagues also discovered fragments of a jaw belonging to a rhinoceros-like animal at a new fossil site in Turkey, which they dated to around 38 to 35 million years ago.
The fossil is probably the oldest Asian-type ungulate found in Anatolia to date and predates the Great Divide by at least 1.5 million years, suggesting that Asian mammals were indeed on their way to Europe via the Balkans.
This southern route to Europe through the Balkanatolias may have been more favourable for adventurous animals than crossing high latitude routes through Central Asia, which at the time were desert steppes.