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12-Ton Jurassic Dino Was the Largest to Walk the Earth

The newly discovered species was massive but walked with a cat-like crouch.
A reconstruction of what the newly discovered dinosaur Ledumahadi mafube may have looked like.

A reconstruction of what the newly discovered dinosaur Ledumahadi mafube may have looked like.

A newly discovered species of dinosaur weighed in at twice the heft of an African elephant and walked with a crouchlike a cat. The dinosaur roamed southern Africa during the early Jurassic Period, some 200 million years ago and, at 12 metric tons, was by far the largest creature on Earth at the time.

Ledumahadi mafube—the name means “giant thunderclap at dawn” in Southern Sotho, a Bantu language of the region—was a distant cousin of the famous sauropod Brontosaurus, but lived millions of years earlier. According to a study, published online at the journal Current Biology, the newly discovered dinosaur was the first truly giant dinosaur known to exist.

Ledumahadi mafube is the first of the giant sauropodomorphs of the Jurassic.

Ledumahadi mafube is the first of the giant sauropodomorphs of the Jurassic.

“Nothing larger than Ledumahadi had ever walked the Earth when it evolved in the earliest Jurassic,” Jonah Choiniere, a senior research on the new study and a reader of dinosaur paleontology at the University of the Witwatersrand in Johannesburg, South Africa, told Live Science.

The first fossils of this dinosaur emerged during a construction project in the late 1980s, when they were found nestled in layers of rock near the border of Lesotho, a mountainous country that South Africa completely encloses. More than a decade later, researchers from the University of the Witwatersrand returned to the site and found more bones. It wasn’t until 2017 that they were able to excavate all its remains, including a wrist bone that helped them determine the dinosaur’s distinctive manner of walking.

"It walked on all fours, but unlike an elephant, which has very rigid, erect legs, its stance would have been more crouched, like a cat or a dog,” Choiniere explained.

By tracing the growth rings in the fossilized bones, the researchers determined the dinosaur was 14 years old, and fully grown, when it died between 195 and 200 million years ago.

Closely spaced growth rings at the periphery of the fossil show that the animal is an adult.

Closely spaced growth rings at the periphery of the fossil show that the animal is an adult.

But its mixture of features initially confused the scientists. Like its famous cousin, Brontosaurus, L. mafube was a giant plant-eater with a long, skinny neck, tiny head and long tail. But while its its back legs were huge, strong and column-like, similar to its later sauropod relatives, its front legs looked smaller and more suitable for grabbing things, like earlier two-legged sauropodomorphs.

L. mafube was a sauropodomorph, they concluded, but a much larger one than they had thought existed this early in the Jurassic. And unlike some earlier sauropodomorphs, L. mafube walked on four legs, not two, although it could rear up on its hind legs if it needed to—to nibble leaves off a tree, for example. The researchers believe the dinosaur adapted this way to make it more stable, which probably allowed it to grow larger than anything else at the time, and would help its later relatives grow even more massive.

As another study co-author, paleontologist Blair McPhee of the Universidade de São Paulo, said to NPR, L. mafube was “the animal that wanted to have it all, that wanted to have everything.”

So while it isn’t the biggest dinosaur ever found, the aptly named “giant thunderclap at dawn” stands out as the earliest known truly giant dino, and a key transitional species that paved the way for the massive beasts that would come later. 

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