Researchers recently discovered something very surprising in one of the largest diamond mines in Africa. The Catoca mine in Angola is home to tracks from animals that date back to roughly 118 million years ago. Dinosaurs, crocodiles, and some species of large mammals once tread through these mines, and left their mark there.

Mammal tracks were first discovered in the mines in 2010 by mine geologist Vladimir Pervov. Pervov got in touch with paleontologist Octávio Mateus, who visited the mine in July 2011 to collect the track marks. The Catoca Diamond Mine halted activity for about eight months to allow paleontologists to dig without disruption when this discovery was made, which is no small measure, because Catoca is the fourth-largest diamond mine in Africa. If the diamond mine, which is privately owned, had decided not to cooperate, this find could have been obliterated from history.

These are the first mammalian fossils ever discovered in the inland part of Angola. All of the other mammalian tracks discovered in Angola were discovered near the coastline. These are also the first dinosaur tracks ever discovered in Angola.

The mammal tracks were unusually large for that time period. All known mammals that long ago were very small, not much larger than rats. The tracks researchers found in the diamond mine belonged to a mammal the size of a raccoon, however. This is the first evidence of any mammals of this size during the early Cretaceous period. The mammal's footprints were roughly 1 inch by 3.7 inches. The researchers estimated its size based on that.

This find came out of the PaleoAngola Project, which seeks to study Angola's paleontology. This project is an international collaboration. From this project, we now know that dinosaurs likely originated in Angola during the Cretaceous period.

Researchers found about 70 distinct tracks in the diamond mine, in a small sedimentary basin. Eighteen of these tracks belonged to sauropods, which were the first dinosaurs to ever be discovered in Angola. The sauropod tracks measure roughly 20 inches.

The researchers also found the track marks of a crocodylomorph, an ancient group that included relatives of modern-day crocodiles.