Turgai Strait

The Turgai Strait, also known as the Turgay/Turgai Sea, Obik Sea, Ural Sea^[1] or West Siberian Sea, was a large shallow body of salt water (an epicontinental or epeiric sea) during the Mesozoic through Cenozoic Eras. It extended north of the present-day Caspian Sea to the "paleo-Arctic" region, and was in existence from the Middle Jurassic to Oligocene, approximately 160 to 29 million years ago.^[2]

The Turgai Strait was not absolutely continuous throughout this entire era, though it was a persistent and predominating feature in its region; it "fragmented southern Europe and southwestern Asia into many large islands, and separated Europe from Asia."^[3]

The division of the Eurasian landmass by the Turgai Sea had the effect of isolating terrestrial animal populations.^[4] Notably, the isolation of Europe by the Turgai Sea led to it developing its own unique fauna via a mixture of Europe-endemic and African-originating lineages. Following the Turgai Strait's disappearance and the extinction of much of Europe's original fauna during the Eocene-Oligocene extinction event, Asian-originating lineages such as water frogs managed to successfully migrate to and colonize Europe, leading to Europe's modern assemblage of taxa with primarily Asian origins.^[5]

The Turgai Strait derives its name from the Turgay Basin of modern-day Kazakhstan, where a stretch of the Turgai River flows.^[6]