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Tracksuits found in Africa and South America show that dinosaurs once traveled on a highway 120 million years ago before the two continents split apart, according to new research.
Paleontologists have discovered more than 260 dinosaur footprints from the Early Cretaceous Period in Brazil and Cameroon, which are now more than 3,700 miles (6,000 kilometers) apart on the other side of the Atlantic Ocean.
The footprints are similar in age, shape and geological context, said Louis L. Jacobs, a paleontologist at Texas Southern Methodist University and lead author of a study describing the tracks published by the Museum of Natural History & Modern Science. Mexico on Monday.
Most of the fossilized prints were created by three-toed theropod dinosaurs, and some probably belonged to four-legged sauropods with long necks and tails or ornithischians, which had bird-like pelvic structures, the co-author said. Diana P.
Vineyard, research associate at SMU.
The trails tell the story of how massive earth movements created ideal conditions for dinosaurs before supercontinents separated into the seven continents we know today.
Lush basins for life
The footprints were preserved in mud and silt along ancient rivers and lakes that once existed on the supercontinent Gondwana, which broke away from the mainland of Pangea, Jacobs said.
“One of the youngest and narrowest geological connections between Africa and South America was the northeastern corner of Brazil located against the coast of Cameroon along what is now the Gulf of Guinea,” Jacobs said. “The two continents were continuous along that narrow stretch, so animals on either side of that nexus could move across it.”
Africa and South America began to drift apart about 140 million years ago. The separation created cracks in the Earth’s crust, and as the tectonic plates beneath South America and Africa moved away, magma in the Earth’s mantle created a new oceanic crust. Over time, the South Atlantic Ocean filled the space between the two continents.
But before this gradual change took place, different types of basins were formed as the Earth’s surface pulled apart. Rivers fed into the basins, creating lakes, Jacobs said.
The authors of the study found evidence of what is known as a half-graben basin in the Borborema region of northeastern Brazil and a similar one in the Koum Basin in northern Cameroon.
“A half graben is an elongated basin formed by pulling the Earth’s surface apart and forming a fault on one side so that the valley floor dips down toward the fault on which movement is occurring,” Jacobs said via email. “Hold your hand in front of you. Tilt your fingers down, indicating movement along the fault. Rivers will flow down the valley and sediments will be deposited and eroded from the high side of the valley.”
Within the two basins, the researchers found dinosaur tracks, ancient river and lake sediments, and fossilized pollen.
“Plants provided food for the herbivores and supported a food chain,” he said. “Dinosaur footprints in the muddy sediments left by the rivers and lakes, including those of carnivores, document that these river valleys may have provided specific routes for life to travel across the continent 120 million years ago.”
While dinosaur fossils can provide unique insights into the types of animals that roamed the planet millions of years ago, their footprints offer other windows into the past.
“Dinosaur tracks are not rare, but unlike the bones that are usually found, the tracks are proof of dinosaur behavior, how they walked, how they ran or otherwise, who they walked with, what environment they walked in they through, which direction they were going, and where they went. when they were doing it,” said Jacob.
It is difficult to tell the specific species of dinosaurs that traveled along the basins, but they represent a larger portrait of the ancient climate and how different types of animals thrived in the environment created by the continental rift.
“If your dog and a coyote walk across the same mud flat, you may know that two dog walkers have walked there, that they are very similar, but you may not know that they are different species. Ditto the dinosaur track situation,” Jacobs said. “All animals have home ranges. All animals expand their ranges. Each animal uses resources as needed depending on availability, which is often seasonal. Herbivores follow nutritious plants; carnivores follow their herbivorous diet.”
At the time, rainfall levels helped create a tropical rainforest type environment with abundant vegetation. Animals arrived in the basins from present-day Africa and South America, contributing to the mixing of their populations.
“Imagine a lush open basin with vegetation for the herbivores followed by the carnivores,” said study co-author Lawrence Flynn, assistant director of the American School of Prehistoric Research and laboratory safety coordinator within the department of human evolutionary biology at Harvard University. “If there is no one on the ‘new’ turf, animals will spread into it, if there is no competition.”
Later, once the continents drifted apart, this disruption was likely a break in genetic continuity, Jacobs said.
The dinosaur tracks were first discovered in Cameroon in the late 1980s, and Jacobs reported on them at the First International Symposium on Dinosaur Tracks and Tracks, convened by paleontologist Martin Lockley, in 1986.
Jacobs then became friends with study author Ismar de Souza Carvalho, who is now a professor within the Department of Geology at the Federal University of Rio de Janeiro. Jacobs was studying dinosaur movements from an African perspective, while Carvalho was studying them from a Brazilian perspective.
As research on basins in Africa and South America continued in the following years, Jacobs and Carvalho and their colleagues reviewed existing and new fieldwork and research to analyze the matching features. The new study is being published in honor of Lockley, who spent his career studying dinosaur footprints.
“We wanted to combine new and evolutionary geological and paleontological evidence to tell a story specifically about where and why and when intercontinental dispersal occurred,” Jacobs said.
“One beauty of this Earth is that any of us can see that Africa and South America fit together like puzzle pieces. It is easy to imagine that, in a connected world, animals, including dinosaurs, could move from place to place.”
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