Meet the Free State dinosaur that made the earth move
Lumbering across the Free State on an endless hunt for grazing to sustain its giant body, a 12-tonne Jurassic dinosaur would have shaken the ground beneath its massive feet.
That’s why a team of international scientists have named the newly discovered creature Ledumahadi mafube, Sesotho for “a giant thunderclap at dawn”.
Team leader Professor Jonah Choiniere, a Wits University palaeontologist, said on Thursday: “The name reflects the great size of the animal as well as the fact that its lineage appeared at the origins of sauropod dinosaurs. It honours both the recent and ancient heritage of southern Africa.”
Sauropods had long necks and tails, small heads and four thick legs, and examples such as the brontosaurus are the largest animals ever to have lived on land. At twice the size of a modern-day African elephant, Ledumahadi mafube was the largest land animal alive nearly 200 million years ago, according to a paper on the new species published in the journal Current Biology.
All sauropods ate plants and stood on four legs, but Choiniere said Ledumahadi evolved its giant size independently from sauropods, and its forelimbs would have been more crouched. This caused the scientific team to consider it an evolutionary “experiment” with giant body size.
“The first thing that struck me about this animal is the incredible robustness of the limb bones,” said lead author Blair McPhee, from Brazil. “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.”
Another team member, Roger Benson from Oxford University in the UK, said the scientists developed a new method, using measurements from the “arms” and “legs”, to show that Ledumahadi walked on all fours.
“Many giant dinosaurs walked on four legs but had ancestors that walked on two legs. Scientists want to know about this evolutionary change, but amazingly, no-one came up with a simple method to tell how each dinosaur walked, until now,” said Benson.
By analysing the fossil’s bone tissue, Jennifer Botha-Brink from the South African National Museum in Bloemfontein established the animal’s age.
“We can tell by looking at the fossilised bone microstructure that the animal grew rapidly to adulthood,” she said. “Closely-spaced, annually deposited growth rings at the periphery show that the growth rate had decreased substantially by the time it died,” indicating that the animal had reached adulthood.
Ledumahadi lived near what is now the town of Clarens, but instead of its current mountains the area was flat and semi-arid at the time.
University of Cape Town palaeoscientist Emese Bordy said: “We can tell from the properties of the sedimentary rock layers in which the bone fossils are preserved that 200 million years ago most of South Africa looked a lot more like the current region around Musina [in Limpopo] ... or the central Karoo.”
Ledumahadi is closely related to gigantic dinosaurs from Argentina that lived at a similar time, and Choiniere said this reinforced the view that the supercontinent of Pangaea was still assembled in the Early Jurassic.
“It shows how easily dinosaurs could have walked from Johannesburg to Buenos Aires at that time,” he said.
Science minister Mmamoloko Kubayi-Ngubane said the discovery underlined the global importance of South African palaeontology.
“Not only does our country hold the Cradle of Humankind, but we also have fossils that help us understand the rise of the gigantic dinosaurs,” she said. “This is another example of South Africa taking the high road and making scientific breakthroughs of international significance on the basis of its geographic advantage, as it does in astronomy, marine and polar research, indigenous knowledge and biodiversity.”
Choiniere, who recently emigrated to SA from the US, said: “South Africa employs some of the world’s top palaeontologists and it was a privilege to be able to build a working group with them and leading researchers in the UK.
“Dinosaurs didn’t observe international boundaries and it’s important that our research groups don’t either.”
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