A team of paleontologists recently found similar sets of Early Cretaceous dinosaur tracks on what are now two different continents. One group is in Brazil and the other is approximately 3,700 miles away in Cameroon. More than 260 tracks show where terrestrial dinosaurs were able to roam freely between Africa and South America millions of years before the two continents split apart. The findings were released on August 23 by the New Mexico Museum of Natural History and Science.
“We determined that in terms of age, these tracks were similar,” study co-author and Southern Methodist University paleontologist Louis L. Jacobs said in a statement. “In their geological and plate tectonic context, they were also similar. In terms of their shapes, they are almost identical.”
[Related: A newly discovered sauropod dinosaur left behind some epic footprints.]
Studying footprints — or fossil footprints — like these is important because they provide clues about how fast dinosaurs and other organisms walked or ran, and even what their skin might have looked like. Compared to the more familiar body fossils of teeth or bones, trace fossils often contain evidence of how these long-dead animals interacted with their environment and can also reveal what their environment may have looked like.
The team believes most of the tracks were made by three-toed theropod dinosaurs. Some were also made by sauropods or ornithischians. The footprints are embedded in the mud and mud along several ancient rivers and lakes and were made 120 million years ago on a single supercontinent known as Gondwana. This supercontinent broke away from the larger landmass of Pangea. Shortly before the connection between Africa and South America was completely severed, lakes formed between the basins.
“The plants fed the herbivores and supported a food chain,” Jacobs said. “Muddy sediments left by rivers and lakes contain dinosaur footprints, including those of carnivores, documenting that these river valleys may have provided specific pathways for life to travel across continents 120 million years ago.”
South America and Africa began to separate about 140 million years ago. This separation caused large cracks in the Earth’s crust called fissures to open along any pre-existing weaknesses in the crust. As the tectonic plates beneath the two continents moved apart, magma from the Earth’s mantle rose to the surface. The magma formed a new oceanic crust as the continents drifted apart. Eventually, the South Atlantic Ocean filled the gap between these new continents.
[Related: Why dinosaur footprints inspired paleontologist Martin Lockley.]
Traces of South America were found in the Borborema region of northeastern Brazil. African footprints were discovered in the Koum Basin in northern Cameroon. Some geological signs of continental drift are present in both places where these dinosaur tracks are found. Geological structures that formed when the Earth’s crust broke apart, called half-graben basins, were present in both areas. These basins have ancient fluvial and lacustrine sediments and fossil pollen that indicate the area is about 120 million years old.
“One of the earliest and closest geologic connections between Africa and South America was the northeast Brazil elbow located opposite what is now the Cameroon coast along 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.”
The article was also a tribute to the late paleontologist Martin Lockley, who spent much of his career studying dinosaur tracks and tracks.