Black Sea–Caspian Steppe Black Sea–Caspian Steppe The Black Sea-Caspian Steppe is an informal name for that part of the Eurasian Steppe that extends south between the Black and Caspian Seas. It is usually treated as part of the Pontic-Caspian steppe which includes the area north of the Black and Caspian Seas, but there is some reason to treat it as a distinct place. Its natural boundaries are the Sea of Azov and Black Sea on the west, the Caucasus Mountains on the south and the Caspian Sea on the east. Its northern boundary may be taken as the triangle formed by the lower
Caspian Sea The water level change within the Caspian Sea is an indirect reason for which plants may not get established. These affect aquatic plants of the Volga Delta, such as "Aldrovanda vesiculosa" and the native "Nelumbo caspica". About 11 plant species are found in the Samur River Delta, including the unique liana forests that date back to the Tertiary period. Reptiles native to the region include spur-thighed tortoise ("Testudo graeca buxtoni") and Horsfield's tortoise. The history of the Caspian sea is divided into two parts: a Miocene stage, determined by tectonic events that correlate with the closing of the Tethys Sea,