Mbiresaurus Raathi: Researchers Discover And Name Africa's Oldest Known Dinosaur

Mbiresaurus raathi is estimated to have been six feet long, and may have weighed between 20 to 65 pounds. The dinosaur probably had a long tail.

An artist's illustration of Mbiresaurus raathi. It is Africa's oldest known dinosaur so far, stood on two legs and its head was relatively small, similar to its dinosaur relatives. The dinosaur had small, serrated, triangle-shaped teeth, suggesting it was an herbivore or potentially omnivore. 

Source : Virginia Tech

An international team of researchers have discovered Africa's oldest known dinosaur. A graduate student from Virginia Tech in Blacksburg, United States, and other palaeontologists were the first to find the skeleton of the dinosaur. 

The study describing the findings was recently published in the journal Nature. Researchers have named the dinosaur Mbiresaurus raathi. It is a sauropodomorph, which is a long-necked, herbivorous dinosaur characterised by leaf-shaped tooth crowns. The skeleton discovered by the palaeontologists is the oldest known dinosaur skeleton ever found in Africa so far. 

In a statement released by Virginia Tech, Christopher Griffin, one of the researchers involved in the study, said 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. 

He added that these are Africa's oldest-known definitive dinosaurs, roughly equivalent in age to the oldest dinosaurs found anywhere in the world. He further said that the oldest known dinosaurs, which are 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. These are mainly northern Argentina, southern Brazil, and India. 

Sterling Nesbitt, an author on the paper, said early dinosaurs like Mbiresaurus raathi show that the early evolution of dinosaurs is still being written with each new find and the rise of dinosaurs was far more complicated than previously predicted. 

What Fossils Were Found Alongside Mbiresaurus raathi?

Palaeontologists discovered an assortment of Carnian-aged fossils alongside Mbiresaurus raathi. These fossils include a herrerasaurid dinosaur, early mammal relatives such as cynodonts, armoured crocodylian relatives such as aetosaurs, and ryhnchosaurs. Herrerasaurids were primitive carnivorous dinosaurs, cynodonts were mammal-like reptiles that lived between 259.5 million to 100.5 million years ago, and ryhnchosaurs were herbivorous dinosaurs characterised by their triangular skulls and elongated, beak-like premaxillary bones. Griffin describes ryhnchosaurs as "bizarre, archaic reptiles". They were found in South America and India in the Triassic period (251.9 to 201.3 million years ago). 

Where Is The Name Mbiresaurus raathi Derived From?

The word Mbiresaurus is derived from Shona (group of culturally similar Bantu-speaking people living in eastern half of Zimbabwe) and ancient Greek roots. According to Virginia Tech, "Mbire" is the name of the district where the dinosaur was found. Mbire is also the name of an historic Shona dynasty that ruled the region. 

Palaeontologists used the species name "raathi" for the newly found dinosaur in honour of Michael Raath, a palaeontologist who first reported fossils in northern Zimbabwe.

What Did Mbiresaurus Look Like?

Mbiresaurus raathi is estimated to have been six feet long, and may have weighed between 20 to 65 pounds. The dinosaur probably had a long tail. The skeleton is missing only some parts of the hands and skull. The discovery was made in northern Zimbabwe.

Mbiresaurus raathi stood on two legs and its head was relatively small, similar to its dinosaur relatives. The dinosaur had small, serrated, triangle-shaped teeth. This suggests that the dinosaur was an herbivore or potentially omnivore. 

Griffin said the researchers never expected to find such a complete and well-preserved dinosaur skeleton. He added that when he found the femur of Mbiresaurus, he immediately recognised it as belonging to a dinosaur. 

Griffin said he immediately knew he was holding the oldest dinosaur ever found in Africa. 

Nesbitt said that 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.

New Theory On Dinosaur Migration

The researchers have a new theory on dinosaur migration, including when and where dinosaurs migrated. 

All the seven continents were once a part of the supercontinent Pangea. The climate across the supercontinent is thought to have been divided into strong humid and arid latitudinal belts. The temperature belts were present in the higher latitudes and intense deserts were located across the lower tropics of Pangea. Earlier, scientists believed that these climate belts influenced and constrained animal distribution across Pangea. 

Griffin said that the early dispersal of dinosaurs should have been controlled by latitude, because dinosaurs initially dispersed under this climatic pattern. He explained that the oldest dinosaurs are known from roughly the same ancient latitudes along the southern temperate climate belt. At that time, the southern temperate climate belt was approximately 50 degrees south. 

Griffin and other palaeontologists targeted northern Zimbabwe on purpose because the country fell along the southern temperate climate belt. The belt was bridging a geographic gap between southern Brazil and India during the Late Triassic Age. 

Climatic bands restricted these earliest dinosaurs to southern Pangea. Later in history, the dinosaurs dispersed worldwide. The researchers developed a novel data method of testing this hypothesis of climatic dispersal barriers based on ancient geography and the dinosaurian family tree, in order to bolster the claim that climatic bands restricted the earliest dinosaurs to southern Pangea. 

According to the study, the breakdown of these climatic barriers, and a wave of northward dispersal of dinosaurs, coincided with a period of intense worldwide humidity, or the Carnian Pluvial Event. 

The barriers returned after this. As a result, the now-worldwide dinosaurs were restricted in their distinct provinces across Pangea for the remainder of the Triassic Period. Griffin said the researchers' 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. 

Brenen Wynd, a researcher who helped build the data model, said the early history of dinosaurs was a critical group for this kind of problem. This is because there is a huge amount of physical data from fossils, and also geochemical data that previously gave a really good idea of when major deserts were present.

Michael Zondo, a curator at the Natural History Museum in Zimbabwe, said Mbiresaurus raathi is the first sauropodomorph find of its size from Zimbabwe. Otherwise, most of the sauropodomorph finds from Zimbabwe are usually of medium-to large-sized animals. 

Moira Fitzpatrick, the director of the Natural History Museum of Zimbabwe, said this is an exciting and important dinosaur find for Zimbabwe, and that the museum has been watching the scientific process unfold with great pride.