Palaeontologists have found and named Africa’s oldest definitive dinosaur.
An international team led by a Virginia Tech graduate student, Christopher Griffin, which found the dinosaur, says at 230 million years old, it’s as old as any dinosaur found anywhere in the world.
Remarkably Griffin and others found a mostly intact skeleton, missing only some of the forearm and portions of the skull.
The skeleton was found in the northern Zimbabwean province of Mbire and the animal has been named Mbiresaurus raathi. The name “raathi” is in honour of Michael Raath, a palaeontologist who first reported fossils in northern Zimbabwe.
Its description has just been published in Nature.
Mbiresaurus is believed to be an early relative of the famous long-necked and massive sauropods like Diplodocus, Brachiosaurus and Apatosaurus.
But, where the true sauropods were huge, lumbering animals weighing up to 80 tonnes and measuring an estimated 30-40 metres longh, Mbiresaurus was a sauropodomorph of much more diminutive dimensions.
Mbiresaurus would have been no longer than two metres and weighed around 10-30 kilograms. It did have a relatively small head and long tail like its sauropod relatives. It sported small, serrated, triangle-shaped teeth, suggesting that it was a plant eater or potentially omnivorous. It probably walked on two legs.
“We never expected to find such a complete and well-preserved dinosaur skeleton,” says Griffin, now a post-doctorate researcher at Yale University.
You can hear Griffin’s exhilaration which he felt when he began digging: “When I found the femur, I immediately recognized it as belonging to a dinosaur and I knew I was holding the oldest dinosaur ever found in Africa. When I kept digging and found the left hip bone right next to the left thigh bone, I had to stop and take a breath – I knew that a lot of the skeleton was probably there, still articulated together in life position.”
Griffin says the discovery has global implications for understanding the evolution of the first dinosaurs.
“The discovery of Mbiresaurus raathi fills in a critical geographic gap in the fossil record of the oldest dinosaurs and shows the power of hypothesis-driven fieldwork for testing predictions about the ancient past.
“These are Africa’s oldest-known definitive dinosaurs, roughly equivalent in age to the oldest dinosaurs found anywhere in the world. The oldest known dinosaurs – from roughly 230 million years ago, the Carnian Stage of the Late Triassic period – are extremely rare and have been recovered from only a few places worldwide, mainly northern Argentina, southern Brazil, and India.”
“The evolution of dinosaurs is still being written with each new find. The rise of dinosaurs was far more complicated than previously predicted,” says co-author Sterling Nesbitt, associate professor of geosciences at Virginia Tech.
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“Chris did an outstanding job figuring out a place to test his ideas about early dinosaur evolution, went there, found incredible fossils, and put it all together in a fantastic collaboration that he initiated,” Nesbitt adds.
Other fossilised animals were found alongside Mbiresaurus , giving a sense of the ecosystem in which the early dinosaur lived.
An assortment of Late Triassic fossils, including a small herrerasaurid dinosaur, early mammal relatives such as cynodonts, armoured early crocodilians such as aetosaurs, and bizarre, archaic reptiles known as rhynchosaurs were found at the site. Many of these animals from this same time period are, again, typically found in South America and India.
Griffin’s team weren’t blindly looking in northern Zimbabwe. They found a pattern which suggested they would be able to find some of the earliest dinosaurs in the region.
Africa was once part of the supercontinent Pangaea. The supercontinent’s climate is thought to have been demarcated into extremes of humidity and aridity along Earth’s latitudes.
Scientists have previously proposed that these climate belts influenced and constrained animal distribution.
“Because dinosaurs initially dispersed under this climatic pattern, the early dispersal of dinosaurs should therefore have been controlled by latitude,” Griffin says. “The oldest dinosaurs are known from roughly the same ancient latitudes along the southern temperate climate belt which was, at the time, approximately 50 degrees south.”
Northern Zimbabwe falls along this same climate belt, bridging a geographic gap between southern Brazil and India during the Late Triassic.
The researchers also conducted data analysis of known branches in the dinosaur family tree to bolster their claim that dinosaurs were restricted to this belt before spreading.
“This two-pronged approach combines hypothesis-driven predictive fieldwork with statistical methods to independently support the hypothesis that the earliest dinosaurs were restricted by climate to just a few areas of the globe,” Griffin adds.
The find also represents an important milestone for palaeontology in Zimbabwe.
“The discovery of the Mbiresaurus is an exciting and special find for Zimbabwe and the entire paleontological field,” says Michel Zondo, a curator and fossil preparer at the Natural History Museum of Zimbabwe. “The fact that the Mbiresaurus skeleton is almost complete, makes it a perfect reference material for further finds. It is the first sauropodomorph find of its size from Zimbabwe, otherwise most of our sauropodomorph finds from here are usually of medium to large-sized animals.”
Much of the Mbiresaurus is being cleaned and studied at Virginia Tech for now, but the whole skeleton and the additional fossils will be permanently kept at Natural History Museum of Zimbabwe.
“This is such an exciting and important dinosaur find for Zimbabwe, and we have been watching the scientific process unfold with great pride,” says Moira Fitzpatrick, the museum’s director. “It has been a pleasure to work with Dr Griffin, and we hope the relationship will continue well into the future.”