Identical dinosaur footprints found on both sides of the Atlantic

An international team of researchers led by paleontologist Louis L. Jacobs of Southern Methodist University has discovered identical sets of dinosaur footprints dating back to the Early Cretaceous period on two now-different continents.

More than 260 dinosaur footprints have been discovered in Brazil and Cameroon, showing where land-dwelling dinosaurs last managed to freely cross between South America and Africa millions of years ago before the continents separated.

“We found that these artifacts were similar in age. They were also similar in geological and plate tectonic context. In terms of their shapes, they were almost identical,” Jacobs said.

The footprints, etched into mud and silt, have been found along ancient rivers and lakes more than 3,700 miles, or 6,000 kilometers, apart. The footprints were left by dinosaurs 120 million years ago on a single supercontinent known as Gondwana — which broke away from the larger landmass of Pangaea, Jacobs said.

“One of the smallest and narrowest geological connections between Africa and South America was the elbow of northeastern Brazil off what is now the coast of Cameroon along the Gulf of Guinea,” Jacobs explained. “The two continents were connected along this narrow stretch, so that animals on either side of this connection could move across it.”

Most of the dinosaur fossils were made by three-toed theropod dinosaurs, said Diana B. Vineyard, a research associate at Southern Methodist University and co-author of the study. A few were likely made by sauropods or birds.

Co-authors of the study included Lawrence J. Flynn of the Department of Human Evolutionary Biology at Harvard University, Christopher R. Scotese of the Department of Earth and Planetary Sciences at Northwestern University, and Ismar de Souza Carvalho of the Federal University of Rio de Janeiro and the Center for Earth Sciences.

The New Mexico Museum of Natural History and Science published the study in honor of the late paleontologist Martin Lockley, who spent much of his career studying dinosaur footprints.

Dinosaur footprints tell the whole story

Africa and South America began to break apart about 140 million years ago, causing cracks in the Earth’s crust, called fissures, to appear along pre-existing weaknesses.

As the tectonic plates beneath South America and Africa moved apart, magma rose from the Earth’s mantle to the surface, creating new oceanic crust as the continents moved apart. Eventually, the South Atlantic Ocean filled the space between the two newly formed continents.

Signs of some of these major events are evident between the two sites where the dinosaur footprints were found—in the Borborma region of northeastern Brazil and the Koum Basin in northern Cameroon. Both areas have semi-bent basins—geological structures formed during rifting as the Earth’s crust separates and cracks form—that contain deposits of ancient rivers and lakes.

In addition to dinosaur tracks, these deposits contain fossil pollen grains dating back up to 120 million years.

Before the continental connection between Africa and South America was severed, rivers flowed and lakes formed in the basins, Jacobs says.

“Plants fed herbivores and supported a food chain. Muddy sediments left behind by rivers and lakes contain dinosaur footprints, including those of carnivores, documenting that these river valleys may have provided specific pathways for life to move across continents 120 million years ago.”