Fabulous 230-million-year-old fossil is Africa’s oldest known dinosaur

A new study has found that the oldest definitive dinosaur species ever discovered in Africa – and one of the oldest dinosaur species to walk the Earth – was discovered in Zimbabwe. The discovery sheds new light on the evolution of dinosaurs and on one of the most fundamental questions of Triassic paleontology: Why did dinosaurs live only in some parts of the ancient supercontinent Pangea?

Scientists began work at the Pebbly Arkose Formation in northern Zimbabwe in 2017. After five years of painstaking excavation and COVID postponements, they finally uncovered the star specimen of the dig: Mbiresaurus raathi, a nearly complete skeleton named after "Mbire," a Shona dynasty. who once ruled the region. The species name is in honor of Michael Raath, who helped discover the first fossils in the area. At around 230 million years old, the specimen is on par with the oldest dinosaurs ever found. Their results were published online Wednesday (August 31) in the journal Nature (opens in a new tab). "The earliest dinosaurs were small -- far from the giants we usually think of," Christian Kammerer, curator of paleontology at the North Carolina Museum of Natural Sciences, who was not involved in the research, told Live Science by email. The newly named dinosaur is a sauropodomorph, a relative of the massive (and iconic) long-necked sauropods like Brachiosaurus and Apatosaurus. At about 6 feet (2 meters) long, or about as long as a Shetland pony, and 1.5 feet (0.5 m) tall at the hips, M. raathi was not tiny, but would have been dwarfed by later sauropods such as the massive 122-foot-long (37 m) Patagotitan. M. raathi lived during the Late Triassic (252 million to 201 million years ago) along the banks of an ancient river in what later became Zimbabwe. It was a rich ecosystem full of not only dinosaurs. "I think a big part of the story is all the different animals we found together," first study author Christopher Griffin, a vertebrate paleontologist at Yale University, told Live Science. Excavations have turned up numerous proto-mammals known as cynodonts, as well as armored crocodiles, bizarre beaked reptiles called rhynchosaurs, and even evidence of early meat-eating dinosaurs.

This grouping almost exactly mirrors fossils that paleontologists might expect to find an ocean away, buried in the steppes of Patagonia or tucked away in the rocky outcrops of Brazil. During the Triassic period, all of Earth's continents were united into one giant landmass known as Pangea. Because of this ancient proximity, many areas now separated by entire oceans—such as the coasts of South America and Africa—once shared flora and fauna. "If you draw a line across Pangea connecting northern Argentina and southern Brazil, you also cross northern Zimbabwe," Griffin said. As a result, M. raathi closely resembles other Late Triassic sauropodomorphs such as the misleadingly named Eoraptor and the dog-sized Saturnalia, both found in Brazil as well as India. It remains a bit of a mystery why certain animal species were pushed into certain areas of Pangea during this time. "You'd think it would be easy to cross a supercontinent," said Steve Brusatte, a paleontologist at the University of Edinburgh in Scotland who was not involved in the study, "but it seems not." However, sites such as the Pebbly Arkose Formation offer clues to this millennia-old mystery. Based on earlier research, the researchers proposed that different climate patterns kept the Triassic animals in place rather than physical boundaries such as oceans. Closely related dinosaurs found in South America, south-central Africa and India suggest that similar animals ranged freely in that particular latitude band, but not outside it, likely due to climatic barriers such as extreme heat or drought, the researchers wrote in the study. .

Dinosaurs likely did not disperse to other parts of Pangea until these climatic barriers were loosened. But the habitats of other large animal groups with roots in the Triassic, including mammals, turtles, amphibians and reptiles, are still affected today by how these climate zones affected those groups' ancestors, the team suggested. Meanwhile, one more dinosaur fossil has been discovered in Africa that may be even older than M. raathi – Nyasasaurus, which was found in a roughly 245-million-year-old fossil formation in Tanzania. However, Nyasasaurus is only known from a handful of bones. Together, they do not form a complete enough skeleton to determine whether it was a true dinosaur or simply a dinosaur ancestor, known as a dinosauromorph. Either way, M. raathi represents a key piece in the dinosaur lineage mosaic. "The discovery of a new species is usually very important to science," said study co-author Darlington Munyikwa, paleontologist and deputy executive director of the National Museums and Monuments of Zimbabwe. And he told Live Science, the fact that the species is the oldest confirmed dinosaur in Africa makes it particularly "amazing." The specimen now resides at the Natural History Museum of Zimbabwe in Bulawayo, where it will inspire generations of paleontologists. "We knew next to nothing about the oldest dinosaurs in Africa, and the discovery of Mbiresaurus changes that," Brusatte said. "I think it's one of the most important recent dinosaur discoveries anywhere on the planet."