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
Avalonia later phases of the Acadian orogeny. This was happening at around the Equator during the later Carboniferous, forming Pangaea with Avalonia near its centre but partially flooded by shallow sea. In the Jurassic, Pangaea split into Laurasia and Gondwana, with Avalonia as part of Laurasia. In the Cretaceous, Laurasia broke up into North America and Eurasia with Avalonia split between them. Iberia was later rotated away again as the African part of Gondwana strike-slipped past it. This last movement caused the Alpine orogeny including the raising of the Pyrenees during the Miocene and Pliocene. As a result of this, part