These predators, known as 'rauisuchians' preyed on early herbivore dinosaurs and their mammal relatives living at the time, according to Rick Tolchard from the University of the Witwatersrand in South Africa.
Giant, predatory crocodile-like animals that lived during the Triassic period in southern Africa preyed on early dinosaurs 210 million years ago, scientists say.
These predators, known as "rauisuchians" preyed on early herbivore dinosaurs and their mammal relatives living at the time, according to Rick Tolchard from the University of the Witwatersrand in South Africa.
"These ancient fossils provide us with evidence of how at least two predator species hunted these vegetarian dinosaurs 210 million-years-ago," Tolchard said.
"It is amazing to follow the clues left behind in fossilised teeth, jaws, limbs and other fossils to help us tell the ancient story of life in southern Africa," he said.
The fossils, described in the Journal of African Earth Sciences, include teeth, pieces of jaws, hind limbs and body armour, all of which can be described as parts of rauisuchians.
Rauisuchians are closely related to crocodiles as we know them today. They had a diversity of body shapes and sizes during the Triassic period, researchers said.
The specimens described in the research include some of the largest carnivorous members of this group, that were possibly up to 10 metres long, with huge skulls full of serrated, curved teeth.
The study shows that the rauisuchians were some of the latest-surviving members of their group and that when they were alive, they were thriving close to the Antarctic Circle -- the theoretical limit for their physiology.
"In the Triassic period, rauisuchians were widespread and their fossils are known from all continents except Antarctica," said Tolchard.
"They went extinct about 200 million years ago, paving the way for dinosaurs to become the dominant large land animals," he said.
"Rick's study demonstrates the value of re-examining old specimens, and now we finally know what was preying on all those herbivorous dinosaurs," said Jonah Choiniere, Rick's advisor and Professor at the Wits Evolutionary Studies Institute.