In the Free State province of South Africa they have found a new dinosaur specimen named Ledumahadi mafube. It is a close relative of the famed brontosaurus, who walked on all fours, anticipating the style of locomotion perfected by it.
Its name comes from one of the 11 official languages of South Africa, Sesotho. It means 'giant thunder at dawn’.
This plant-eating dinosaur dates back much farther than its relatives in the prehistoric past of the first Jurassic.
"It shows us that even 200 million years ago, these animals had already become the largest vertebrates that ever walked the Earth," says Jonah Choiniere of the University of the Witwatersrand in Johannesburg, South Africa, the institution leading the research. published in the journal Current Biology.
Choiniere explains that he first saw the specimen after his student and first author on the work, Blair McPhee, showed him the bones in 2012, shortly after Choiniere moved to South Africa.
"Blair told me how important he thought it was and even showed me that some of his bones were still sticking out of the rocks in the field!" He recalls. Together, they and a team of scientists began excavating the skeleton over a period of years.
Ledumahadi was twice the size of a large African elephant
It was obvious that Ledumahadi was quite large. Researchers estimate that it was the largest land animal that existed on Earth when it lived. The discovered specimen represented an adult of about 14 years of age. Most likely, it weighed about 12 tons and was 4 meters high from the hip.
“Its name reflects the large size of the animal, as well as the fact that its lineage appeared in the origins of the sauropod dinosaurs. It honors the recent and ancient heritage of southern Africa, ”says Choiniere.
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"The first thing that struck me about this animal is the incredible strength of the limb bones," says McPhee. 'It was about the same size as the gigantic sauropod dinosaurs, but while the limbs of these animals are quite slender, those of Ledumahadi are incredibly thick. To me, this indicated that the path to gigantism in sauropodomorphs was far from easy, and that the way in which these animals solved common life problems, such as eating and moving, was much more dynamic within the group than is known. I thought previously, "he adds.
The Quadruped Evolution of Dinosaurs
Knowing the biology of these extinct animals is extremely difficult. To determine whether it walked on two legs like its ancestors or four, the researchers had to develop a method that uses the measurements of current animals. The method consisted of calculating the thickness of Ledumahadi's limbs to infer his weight and the number of limbs that that weight had to have supported.
The team also showed that many pre-sauropod relatives got on all fours and that this body posture evolved more than once. Also, it appeared earlier than scientists thought.
“Many giant dinosaurs walked on four legs but had ancestors who walked on two. Scientists want to know more about this evolutionary change, but surprisingly, no one came up with a simple method to count how each dinosaur walked, until now ", says Roger Benson, of the University of Oxford (UK).
By analyzing the bone tissue of the fossil, Jennifer Botha-Brink of the South African National Museum in Bloemfontein established the age of the animal: “We can see through its fossilized bone microstructure that the animal grew rapidly into adulthood. The growth rings deposited annually on the periphery show that the growth rate had decreased substantially at the time of their death. ' This indicates that the animal had reached adulthood.
A species in time of transition
With the study of bone tissues it was also shown that Ledumahadi represents a transitional stage between these two main groups of dinosaurs.
«The evolution of sauropods is not as simple as we thought. In fact, it appears that sauropodomorphs evolved four-legged postures at least twice before they could walk with their limbs erect, which undoubtedly helped them to be so successful in an evolutionary sense, ”says Choiniere.
More broadly, the results show that millions of years before the tyrannosaurus or velociraptor appeared in the northern hemisphere, 'there was a thriving ecosystem of dinosaurs here in South Africa, at the bottom of the world, with 12-ton giants like Ledumahadi, tiny carnivores like the Megapnosaurus, the first mammals, some of the first turtles and many others ”, he concludes.
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