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| Mbiresaurus raathi Griffin, Wynd, Munyikwa, Broderick, Zondo, Tolan, Langer, Nesbitt & Taruvinga, 2022 Artwork: Andrey Atuchin |
Abstract
The vertebrate lineages that would shape Mesozoic and Cenozoic terrestrial ecosystems originated across Triassic Pangaea. By the Late Triassic (Carnian stage, ~235 million years ago), cosmopolitan ‘disaster faunas’ had given way to highly endemic assemblages on the supercontinent. Testing the tempo and mode of the establishment of this endemism is challenging—there were few geographic barriers to dispersal across Pangaea during the Late Triassic. Instead, palaeolatitudinal climate belts, and not continental boundaries, are proposed to have controlled distribution. During this time of high endemism, dinosaurs began to disperse and thus offer an opportunity to test the timing and drivers of this biogeographic pattern. Increased sampling can test this prediction: if dinosaurs initially dispersed under palaeolatitudinal-driven endemism, then an assemblage similar to those of South America and India—including the earliest dinosaurs—should be present in Carnian deposits in south-central Africa. Here we report a new Carnian assemblage from Zimbabwe that includes Africa’s oldest definitive dinosaurs, including a nearly complete skeleton of the sauropodomorph Mbiresaurus raathi gen. et sp. nov. This assemblage resembles other dinosaur-bearing Carnian assemblages, suggesting that a similar vertebrate fauna ranged high-latitude austral Pangaea. The distribution of the first dinosaurs is correlated with palaeolatitude-linked climatic barriers, and dinosaurian dispersal to the rest of the supercontinent was delayed until these barriers relaxed, suggesting that climatic controls influenced the initial composition of the terrestrial faunas that persist to this day.
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| Skeletal anatomy of the Mbiresaurus raathi holotype (NHMZ 2222) and paratype (NHMZ 2547). |
Systematic Palaeontology
Dinosauria Owen, 1842
Saurischia Seeley, 1887
Sauropodomorpha von Huene, 1932
Mbiresaurus raathi gen. et sp. nov.
Etymology. From Mbire, an historic Shona empire and district containing the study area, and σαûρος (saûros), Greek for reptile; raathi after Michael Raath, who with others first reported fossils from the Dande area29, to honour his contribution to Zimbabwean palaeontology and the fossil heritage of Zimbabwe.
Locality and horizon. From the midsection of the ?late Carnian Pebbly Arkose Formation30,31, Dande Communal Land, Mbire District, Mashonaland Central Province, Zimbabwe. Coordinates for specific localities are available on request through C.T.G. and NHMZ. See the Supplementary Information for detailed justification of formation age.
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| Artistic reconstruction of the dinosaur Mbiresaurus raathi (foreground) with the rest of a new Zimbabwean animal assemblage in the background. This assemblage includes two rhynchosaurs (front right), an aetosaur (left) and a herrerasaurid dinosaur that is chasing a cynodont (back right). Artwork: Andrey Atuchin |
Christopher T. Griffin, Brenen M. Wynd, Darlington Munyikwa, Tim J. Broderick, Michel Zondo, Stephen Tolan, Max C. Langer, Sterling J. Nesbitt and Hazel R. Taruvinga. 2022. Africa’s Oldest Dinosaurs reveal early Suppression of Dinosaur Distribution. Nature. DOI: 10.1038/s41586-022-05133-x
