Nearctic realm represented by the Madrean Region. Although North America and South America are presently joined by the Isthmus of Panama, these continents were separated for about 180 million years, and evolved very different plant and animal lineages. When the ancient supercontinent of Pangaea split into two about 180 million years ago, North America remained joined to Eurasia as part of the supercontinent of Laurasia, while South America was part of the supercontinent of Gondwana. North America later split from Eurasia. North America has been joined by land bridges to both Asia and South America since then, which allowed an exchange of
South China (continent) Ocean. By the Late Carboniferous (300 million years ago), while North China collided with Siberia and Kazakhstania, completely closing the Proto-Tethys Ocean, South China became an independent continent. For much of the Permian Period, South China remained in the tropical latitudes. And also, while most of the giant lycopods of the Carboniferous disappeared, giant lycopods remained in South China, since its isolation from the now formed Pangaea. Cimmeria, a microcontinent that consisted of today's Tibet, Iran, Turkey, and parts of Southeast Asia rifted away from Gondwana (just as North and South China did earlier), and was heading towards Laurasia. Paleo-Tethys