Much of the theory of continental drift (now referred to as plate tectonics) derives from evidence provided by fossils. Scientists have been collecting parallel evidence across the Pacific Ocean since the early 1900s. This evidence, which includes reptile fossils of matching genus, shows clearly that the Earth's modern land masses were once close together and, likely, physically joined.
History
In 1915, German scientist Alfred Wegener developed a theory that the continents we know today were once joined as a single land mass. He called the land mass Pangaea, a term that means "all lands" in Greek. A South African geologist by the name of Alexander Du Toit added to the theory, suggesting evidence that described how the supercontinent split and drifted apart. The scientists based a significant portion of their theories on evidence from the fossil record.
Significance
Paleontologists discovering matching fossils in Africa and South America contributed greatly to the evidence behind the theory of continental drift. It seems to prove that these continents were once close enough to each other that animals and plants could easily move between them. Notably, the fossils in question were found embedded in the same geologic layer sequence. This suggests that the living organisms from which the fossils derive lived in the same ecosystem and soil, even though they were found thousands of miles apart.
Types
There are hundreds of fossil types that have turned up in Africa and South America. Four of these include the Cynognathus (a mammal-like land-dweller found in South America, Africa, China and Antarctica), Lystrosaurus (a pig-sized herbivore found in Africa, Antarctica, and India), Mesosaurus (a freshwater-dwelling anapsid reptile found in Africa and South America) and Ichthyosaurs (another aquatic reptile, shaped like a 45-foot-long dolphin, found in Africa and Chile.)
Geography
The division of Pangaea began 250 million years ago and occurred in four distinct stages. First, a rift began within Pangaea and split the supercontinent into two parts, Laurasia and Gondwanaland. Next, the Atlantic expanded and pushed apart North America and Africa. Antarctica then severed from Gondwanaland while India shifted toward the equator. South America and Africa split during the third stage, pushing Africa north. Finally, Greenland broke away from continental Europe and North America.
Theories/Speculation
The 2004 discovery of a rare fossilized dinosaur led scientists to believe that the continents might have been connected by a land bridge almost 25 million years after previous researchers had theorized. The fossil in question, Rugops primus, is that of a large carnivore found in South America and the Sahara Desert.
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