There was a time when the scientific community thought the idea of “continental drift” was absurd. Scientists thought that German geophysicist Alfred Wegener, who proposed the hypothesis in 1912, was a quack. Things have changed a lot since then, and experts now accept the proposal as science, with several different lines of evidence supporting Wegener’s theory about the supercontinent Pangaea. In fact, we recently learned about new clues.
The discovery. A group of paleontologists identified almost the same set of dinosaur footprints in Cameroon in Central Africa, and Brazil in South America. In other words, they’ve found identical footprints from millions of years ago only separated by more than 4,000 miles.
The discovery sites aren’t a minor matter. They could represent one of the last places where creatures could move freely between land masses before the continent of Gondwana, a fragment of Pangaea, completely separated some 120 million years ago.
Hundreds of tracks. The researchers found 260 tracks on both continents, another sign that the two spaces were once connected. The tracks were similar in age, about 120 million years old. Dinosaurs once walked in the mud and silt on the banks of ancient rivers and lakes, leaving these footprints behind. The footprints are known as trace fossils because they trace the animals that left them. Most were made by theropods, a group of three-toed and bipedal carnivorous dinosaurs.
Theropods such as Tyrannosaurus rex and Allosaurus were some of the most famous dinosaurs identified in the footprints sets. Other samples included hundreds of tracks from sauropods and ornithischians, which get their names because of the bird-like nature of their hip bones.
Gondwana. The researchers recreated the possible scene in their work. At that time, the Earth was a supercontinent. The footprints they found in South America were in the Sousa Basin, the region in eastern Brazil that would fit neatly into the African coast along the Gulf of Guinea. The Brazilian tracks are more than 4,000 miles from the Cameroonians, demonstrating that dinosaur populations roamed both sites when they were still connected.
According to a statement from SMU paleontologist Louis Jacobs, lead author of the study, “One of the youngest and narrowest geological connections between Africa and South America was the elbow of northeastern Brazil nestled against what is now the coast of Cameroon along the Gulf of Guinea. The two continents were continuous along that narrow stretch, so that animals on either side of that connection could potentially move across it.”
The puzzle that fits. Over the years, researchers have found enough clues to piece together what was once a supercontinent that began to fragment about 175 million years ago. This gigantic landmass united all the planet’s land masses into one, surrounded by a vast ocean called Panthalassa. The splitting of Pangaea led to the formation of the continents we know today, and its existence is fundamental to understanding plate tectonics and the geographic distribution of species and climates throughout Earth’s history.
As what is now Africa and South America began to separate, cracks formed in the crust, and a gap began to widen between the two parts of Gondwana. In these cracks, magma flowed up from below and solidified into a new crust that would form the floor of the Atlantic Ocean. As the two new continents continued to separate, the points where animals could move between them became smaller and fewer in number until the sea separated land and “life.”
Image | SMU
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