Mbiresaurus raathi is, according to a new study published in Nature , the oldest dinosaur species ever discovered in Africa . It is a remarkably small sauropodomorph , a relative of long-necked sauropods such as Brachiosaurus and Apatosaurus . M. raathi would have been 2 meters long and half a meter tall from floor to hip. The specimen is believed to be about 230 million years old , making it among the oldest dinosaurs ever found.
After five years of work interrupted by the COVID pandemic, the team of scientists led by Christopher Griffin of the Virginia Tech School of Sciences has unearthed the almost complete skeleton of the sauropodomorph. It is only missing a part of the hand and parts of the skull. It has been named Mbiresaurus raathi , Mbire after the district where it was found and also a dynasty that once ruled the region, and raath after Michael Raath, who helped discover the first fossils in the area.
“The discovery of Mbiresaurus raathi fills a critical geographic gap in the earliest dinosaur fossil record and shows the power of hypothesis-based fieldwork to test predictions about the ancient past,” Griffin said, adding: “These they are the oldest known definitive dinosaurs from Africa, roughly equivalent in age to the oldest dinosaurs found anywhere in the world The oldest known dinosaurs – from about 230 million years ago, the Carnian stage of the late Triassic period – they are extremely rare and have only been recovered from a few locations worldwide, mainly northern Argentina, southern Brazil, and India.”
Sterling Nesbitt is an associate professor of geosciences and also an author of the study. “Early dinosaurs like Mbiresaurus raathi show that early dinosaur evolution continues to be written with each new find and that the rise of dinosaurs was much more complicated than had been predicted ,” he said.
The finding of Mbiresaurus raathi and other fossils
In addition to Mbiresaurus raathi , scientists have found other fossils of Carnian creatures such as protomammals known as cynodonts, armored crocodiles, rare beaked reptiles called rhynchosaurids, and even what may be evidence of the first carnivorous dinosaur.
According to scientists, M. raathi stood on two legs and its head was relatively small , like that of dinosaurs. It is believed that it was herbivorous since it has small, jagged, triangle-shaped teeth.
“We never expected to find such a complete and well-preserved dinosaur skeleton,” said Griffin, who is now a postdoctoral researcher at Yale University. “When I found the femur of Mbiresaurus , I immediately recognized that it belonged to a dinosaur and knew that I had in my hands the oldest dinosaur ever found in Africa. When I continued to dig and found the left hip bone right next to the left thigh bone , I had to stop and take a deep breath: I knew that much of the skeleton was probably there, still articulated in a living position.
New theory about the dispersal of dinosaurs
The discovered fossil assemblage, which includes M. raathi , protomammals and other reptiles, could well be an ocean away, buried in Patagonia or Brazil.
During the Triassic the continents were united into one giant. It is what is known as Pangea. Many regions that today are separated by entire oceans such as the coasts of South America and Africa were united and shared flora and fauna. “If you draw a line through Pangea connecting northern Argentina and southern Brazil, you cross northern Zimbabwe as well,” Griffin said. That is why M. raathi is very similar to Late Triassic sauropodomorphs found in Brazil and even in India. It is still a mystery why certain species of animals stayed in certain areas of Pangea at that time.
However, deposits such as the Pebbly Arkose Formation shed light on this enigma. Based on previous research, scientists have proposed that it was not physical limits that kept animals in one area or another during the Triassic, but the existence of varied weather patterns .
Closely related dinosaurs found in South America, south-central Africa, and India indicate that similar animals roamed freely through this particular latitude band, but not outside of it. This was probably due to the existence of climatic barriers such as extreme heat or drought , the researchers say in their study.
It is likely that the dinosaurs did not spread to other parts of Pangea until these climatic barriers were relaxed. However, the team suggested that the terrains of other large animal groups with roots in the Triassic, such as mammals, turtles, amphibians and reptiles, are still influenced today by how these climatic bands affected the ancestral groups.
Meanwhile, there’s another dinosaur fossil discovered in Africa that may be even older than M. raathi : Nyasasaurus , which was found in a fossil formation some 245 million years old in Tanzania. However, there are only a few bones of the reptile. Taken together, they do not form a complete enough skeleton to determine whether it was a true dinosaur or simply a dinosaur or dinosauromorph ancestor.
The skeleton of M. raathi is now in the Natural History Museum of Zimbabwe.
Referencia: Griffin, C.T., Wynd, B.M., Munyikwa, D. et al. 2022. Africa’s oldest dinosaurs reveal early suppression of dinosaur distribution. Nature. DOI: https://doi.org/10.1038/s41586-022-05133-x
