Dinosaurs may have first evolved in the Sahara and Amazon rainforest

Many think dinosaurs first emerged on land well south of the equator that now forms part of Argentina and Zimbabwe, but they may have actually arisen in tougher conditions near the equator

By Michael Marshall

23 January 2025

Life would have been particularly hot and dry if dinosaurs really did emerge near the equator

Mark Witton/The Trustees of the Natural History Museum, London

Dinosaurs may have first evolved close to the equator, not in the far south of the southern hemisphere as previously thought. A modelling study suggests they originated in a region that covers what is now the Amazon rainforest, Congo basin and Sahara desert.

“When you consider the gaps in the fossil record and the evolutionary tree of dinosaurs, it could very likely be a centre point for where dinosaurs originated,” says Joel Heath at University College London.

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Dinosaurs evolved some time during the Triassic Period, which ran from 252 to 201 million years ago, but Heath says there is “pretty huge” uncertainty about where and when. The oldest known fossils of these animals are about 230 million years old, but they are distinct enough to suggest that dinosaurs had already existed for a few million years. “There must have been a lot going on in terms of dinosaur evolution, but we just don’t have the fossils,” he says.

At this time, Earth looked very different. All the continents were joined into a single supercontinent called Pangaea, which was shaped like a C with its middle straddling the equator. South America and Africa were in the southern hemisphere segment of this, where they fitted together like jigsaw pieces. The earliest known dinosaurs are from southern parts of those two continents, in places such as modern Argentina and Zimbabwe – so this was thought to be their point of origin.

To learn more, Heath and his colleagues built computer models to work backwards in time from the oldest known dinosaurs to the origin of the group. They created several dozen versions, to take into account uncertainties such as gaps in the fossil record, possible geographic barriers and ongoing doubts over how the earliest dinosaurs were related to each other.