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Paleontologists discovered what they said was a completely new sauropodomorphic dinosaur completely unexpected that lived 200 million years ago (Jurassic period) in South Africa.
A reenactment of the artist Ledumahadi mafube foraging in Lower Jurassic of South Africa; in the foreground, Heterodontosaurus. Image credit: Viktor Radermacher, University of the Witwatersrand.
Appointed Ledumahadi mafube, the new dinosaur species weighed 12 tons, measured about 4 meters high at the hips and is one of the closest relatives of sauropod dinosaurs.
Sauropods, weighing up to 60 tons, include well-known species like brontosaurus. They ate plants and stood on all fours, with a posture similar to that of modern elephants.
Ledumahadi mafube has evolved its giant size regardless of sauropods.
"It shows that 200 million years ago, these animals had already become the largest vertebrates ever to have walked on Earth," said Professor Jonah Choiniere, a researcher at the University's Institute of Evolutionary Studies. of the Witwatersrand.
"Many giant dinosaurs walked on all fours, but their ancestors walked on two legs," said Professor Roger Benson, a scientist in the Department of Earth Sciences at Oxford University and the Institute for Evolutionary Studies. from the University of the Witwatersrand.
"Paleontologists want to know more about this evolutionary change, but surprisingly, no one has come up with a simple method to tell how each dinosaur worked, until now."
Selected preserved items from Ledumahadi mafube and geography and stratigraphy of the type locality: (A) middle / posterior cervical vertebra in left lateral view; (B) anterior dorsal vertebra in the anterior and right lateral views; (C) middle dorsal vertebra in the posterior and right lateral views; (D) first and second "primordial" sacred vertebrae in left lateral view; (E) anterior caudal vertebra in left lateral view; (F) right ulna in the proximal and medial views; (G) first metacarpal in proximal and dorsal / ventral views; (H) third left metacarpal in proximal and ventral views; (I) ungual pedal in lateral and proximal views; (J) anterior chevron in posterior view; and (K) distal right femur in distal, lateral, and anterior views; (L) simplified geological map of the Elliot Formation in South Africa Republic and Lesotho indicating the location of Beginsel Farm and the aerial extent of the outcrop area of the Elliot Formation; (M) landscape view of local geology at the Ledumahadi site; note that contact of the lower and upper Elliot formations (LEF and UEF, respectively) has been identified at 5,530 feet (1,685 m) above sea level; thus, the UEF is 197 feet (60 m) thick; the poorly exposed LEF, which is 33 feet (10 m) thick, contains only massive mudstones with poorly developed pedogenic alterations, green-gray mottles, and very rare drying cracks. Abbreviations: previous process; ns – spine; op-olecranial process; poz – postzygapophysis; rf – radial fossa; sr – sacred ribs; tfc – tibio-fibular ridge; vt – ventral tubercle. Scale bars – 5 cm. Image credit: McPhee et al, doi: 10.1016 / j.cub.2018.07.063.
To determine if Ledumahadi mafube walking on two legs, like his ancestors, or four, researchers have developed a method using the measures of animals today
The method consisted of taking measurements of the thickness of the members of a dinosaur to deduce their weight and the number of members of that weight that had to have been transported.
The results of the team suggest not only that this dinosaur was a quadruped, but also that many other sauropodomorphic dinosaurs (often called "prosauropods") were experimenting with crawling.
"The discovery shows that gigantic body sizes were possible among the first four-legged prosauropods, from two-legged pre-species," paleontologists said.
"However, the first quadrupeds did not possess columnar postures, similar to those of elephants, later sauropod species such as brontosaurus. "
"The evolution of sauropods is not as simple as we thought," said Professor Choiniere.
"In fact, it seems that sauropodomorphs evolved at least twice with a four-legged posture before they could walk with straight limbs, which no doubt contributed to their success in an evolutionary sense.
"More generally, the results show that millions of years before Tyrannosaurus or Velociraptor came on the scene in the northern hemisphere, there was a thriving ecosystem of dinosaurs here in South Africa at the bottom of the world, with giants of 12 tons like Ledumahadi mafube, small carnivores like Megapnosaurus, the first mammals, some of the first turtles and many others, "he said.
"Africa, and especially South Africa, is known for its big game. I think we should be just as famous for our great game of the early Mesozoic, 200 million years ago. "
The results appear in the review Current Biology.
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Blair W. McPhee et al. One of the oldest Jurassic giant dinosaurs in South Africa and the transition to quadrupedality of the early Sauropodomorphs. Current Biology, published online September 27, 2018; doi: 10.1016 / j.cub.2018.07.063
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