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
Saltoposuchus in newly found ecological niches, Pangaea started splitting into Laurasia and Gondwana, and the air was very arid with hot summers and cold winters. After marine life had been wiped out by the mass extinction event, the Triassic waters were populated with very few families of fish. The Triassic Period showed the first development of modern stony corals and a time of modest reef building activity in the shallower waters of the Tethys near the coasts of Pangaea. During the Mesozoic Era, early mammals, reptilian species, and other insects populated the land. Insects that had survived the mass extinction and