Researchers have discovered the fossils of a new dinosaur species that's been hailed as the "first true giant" to have evolved on Earth.
The new species, called Ledumahadi Mafube, lived around 200 million year ago during the Jurassic era. Its name translates to "A giant thunderclap at dawn" in the local Sesotho language where it was found in South Africa's Free State province.
"The name reflects the great size of the animal as well as the fact that its lineage appeared at the origins of sauropod dinosaurs," says Jonah Choiniere, study author and palaeontology professor at the University of the Witwatersand in Johannesburg.
"It honours both the recent and ancient heritage of southern Africa," he adds.
Sauropods, weighing up to 60-tonnes, include well-known species like Brontosaurus, Prof Choiniere explains in the journal Current Biology. All sauropods ate plants and stood on four legs, with a posture like modern elephants.
Two hundred million years ago, South Africa was a very different place, Prof Choiniere explains in a video published on YouTube. The region would have had vast flood plains spreading out into the distance.
The Cape Fold Mountains would have been about the same size as the Himalayas, he says, and they were shedding rock and sediment into the area below. Those rocks covered up the skeletons of animals that had died there - including Ledumahadi Mafube.
Prof Choiniere said the first Ledumahadi Mafube fossil was discovered 30 years ago by a professor from the University of the Witwatersand, who brought the fossils back and kept them stored away. Scientists later returned to the spot where more fossils were uncovered.
"This animal is completely enormous. Its toenail is the length of my hand," says Prof Choiniere.
It was the biggest animal alive on Earth at that time - twice the size of an African elephant today - standing at around four metres high from the hip.
The largest dinosaur species ever discovered, Argentinosaurus huinculensis, lived in the late Cretaceous period over 96.6 million years ago. It's thought these dinosaurs might have evolved from Ledumahadi Mafube.
"The first thing that struck me about this animal is the incredible robustness of the limb bones," said lead author, Dr Blair McPhee, talking about the discovery of Ledumahadi Mafube.
"It was of similar size to the gigantic sauropod dinosaurs, but whereas the arms and legs of those animals are typically quite slender, Ledumahadi's are incredibly thick."