About 210 million years ago, the supercontinent of Pangea was just starting to break up. At the time, dog-sized dinosaurs hid from the predators at the top of the food chain: reptiles called phytosaurs and rauisuchids. Now, with the discovery of an ancient tooth, scientists have found that these predators may have interacted with each other far more often than previously thought.

While phytosaurs dominated the sea, rauisuchids ruled the land, so until now scientists believed that the two prehistoric predators had no reason to tangle with one another.

"Phytosaurs were thought to be dominant aquatic predators because of their large size and similarity to modern crocodylians," Michelle Stocker, one of the researchers, said in a statement, "but we were able to provide the first direct evidence they targeted both aquatic and large terrestrial prey."

In this case, they found the tooth of a phytosaur lodged in the thigh bone of a rauisuchid that was 25 feet long and four feet high at the hip. So not only did these two ancient creatures interact with one another, but they did so on purpose.

"We came across this bone and realized pretty quickly we had something special," said Sterling Nesbitt, vertebrate paleontologist with Virginia Tech's Department of Geosciences.

The researchers came across the bone by chance at the University of California Museum of Paleontology in Berkeley. It goes to show that they still have much to learn about some of the first large reptiles to roam our planet.

"This research will call for us to go back and look at some of the assumptions we've had in regard to the Late Triassic ecosystems," Stocker said. "The distinctions between aquatic and terrestrial distinctions were over-simplified and I think we've made a case that the two spheres were intimately connected."

The findings were published in the journal Naturwissenschaften.