Throughout history, more than a dozen continents and configurations have disappeared. The “supercontinent cycle” sees continents combine and break apart every 300-500 million years. Pangea was the last supercontinent, existing 200 million years ago. Dinosaurs evolved on Pangea, and when it broke apart, they differentiated based on their home continent. The remaining continents became home to mammals, with different groups evolving on each continent. Eventually, the continents split apart, leading to faunal interchanges. North and South America touched three million years ago.
Throughout Earth’s known history, there are more than a dozen continents and continental configurations that no longer exist today. At the largest level, they tend to follow the “supercontinent cycle”: continents combine to form one giant supercontinent, then break up again into separate continents, then the process repeats again. A complete cycle occurs about once every 300-500 million years. The last supercontinent was Pangea, which existed about 200 million years ago, and before that, Rodinia, which existed about 700 million years ago.
Some of the more famous continental configurations that no longer exist today are Pangea (which contained the entire land mass of the world except a small part of present-day China), Gondwana (South America, Africa, Australia and Antarctica all merged together), Laurasia ( North America and Eurasia together), Baltica (a small subcontinent consisting of the present-day Baltic states), India (formerly an independent subcontinent), and the continent of Kerguelen (a continent in the southern Indian Ocean that sank under water 20 million years ago) .
The best known of all the ancient continents is Pangea. Formed about 250 million years ago, just after the worst mass extinction ever on Earth, Pangea persisted for about 70 million years, until it broke into three pieces – Laurasia, Gondwana and Africa – about 180 million of years ago. Pangea was a C-shaped landmass straddling the equator that consisted of more than 98% of today’s total land area. Pangea was so large that it would have been possible for animals to walk from the South Pole to the North Pole only over land. This was the only known time when such a thing was possible. A continuous north-south landmass also encouraged oceanic mixing, which meant that the temperature was relatively warm and uniform across the surface of the Earth.
Dinosaurs initially evolved on Pangea. The earliest dinosaur faunas were global in extent and all ate the same food: cycads, conifers and each other. So when Pangea began dividing 180 million years ago, dinosaurs began to differentiate strongly based on their home continent. Three groups split from each other based on the three major continents at the time. About 130 million years ago, South America began to move away from Africa, leading to the creation of an actual Atlantic Ocean by 110 million years ago. About 60 million years ago, just after the extinction of the dinosaurs, North America began to separate from Eurasia, creating the Norwegian Sea.
The remaining continents – Laurasia, South America/Antarctica, Africa, Australia, have become home to the new dominant creatures on Earth, the mammals. Already 90 million years ago, the first members of the mammalian clade Laurasiatheria (hoofed animals, moles, shrews, bats, carnivores, hedgehogs, cetaceans and many others) and Euarchontoglires (rodents, lagomorphs, shrews and primates) evolved on the continent of Laurasia. Meanwhile, the superorder Afrotheria (golden moles, elephant shrews, tenrecs, aardvarks, hyraxes, elephants, manatees, and others) evolved on the insular African continent. Australia and South America were dominated by marsupials. Eventually, Laurasia split apart, splitting those groups in two, and Africa collided with Eurasia, trading fauna between the two. Just three million years ago, North America touched South America at Panama, and the most recent faunal interchange occurred, mostly to the detriment of South American animals.
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