Mbiresaurus

Chapter • Meet the dinosaur

Overview

Mbiresaurus raathi was a small, lightly built dinosaur that would barely have reached an adult human's waist. It measured roughly 1.6–1.8 metres from snout to tail tip, though much of that length was taken up by a long, slender tail, and it weighed somewhere between ten and thirty kilograms. It walked on two legs, with long hind limbs, short grasping forelimbs, a moderately long neck and a small head filled with leaf-shaped, coarsely serrated teeth. Unlike many later theropods, it had no feathers, and unlike the armoured dinosaurs it had no bony plates: its body was covered in ordinary scaly reptilian skin, as in other early sauropodomorphs. As a biped, Mbiresaurus carried its body horizontally with the tail held clear of the ground as a counterbalance — it never dragged its tail. The slim limb bones and lightweight skeleton suggest a nimble animal that relied on speed to escape the crocodile-line archosaurs and early predatory dinosaurs that shared its floodplains. Its hands were probably capable of hooking or pulling down vegetation, and the flexible neck let it browse at different heights without moving its whole body. The shape of its teeth — leaf-like blades with coarse serrations — is characteristic of plant-eating sauropodomorphs, so Mbiresaurus is interpreted as a herbivore feeding on ferns, seed ferns, conifer foliage and other low-growing Triassic plants. Some researchers argue that the very earliest sauropodomorphs may have been partly omnivorous and occasionally taken insects or small prey, but the dentition of Mbiresaurus points mainly towards a plant diet. The fossils were collected during fieldwork in 2017 and 2019 in the Pebbly Arkose Formation of the Zambezi Valley in northern Zimbabwe, by an international team led by palaeontologist Christopher Griffin. The species was described in the journal Nature in 2022 on the basis of a nearly complete skeleton — the most complete early dinosaur skeleton yet recovered in Africa. The genus name refers to Mbire, the district where the fossils were found and the name of a historical Shona dynasty, while the species name raathi honours the Zimbabwean palaeontologist Michael Raath.

Chapter • Where it lived

Habitat

Mbiresaurus lived about 230 million years ago, during the Carnian stage of the Late Triassic, in what is now northern Zimbabwe. Its fossils come from the Pebbly Arkose Formation in the Zambezi Valley, in Mbire District. At that time all continents were joined in the supercontinent Pangaea, and the region lay far to the south, at roughly the same latitude as southern South America today. The landscape was one of river floodplains with meandering channels and humid stands of conifers, seed ferns and ferns. The same beds have yielded early herrerasaurid-type predatory dinosaurs, herbivorous rhynchosaurs, cynodonts and aetosaurs — a community strikingly similar to the contemporaneous faunas of Argentina and southern Brazil.

Chapter • Wild behavior

Behavior & Ecology

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Chapter • Scientific place

Taxonomy