The mystery behind the origins of the dinosaurs may have been given a new twist, with a modeling study suggesting they may have evolved in what is today equatorial Africa and South America.
This would have represented a far warmer and arid setting for the birthplace of the iconic group than was traditionally assumed.
“Dinosaurs are well studied, but we still don’t really know where they came from,” said paleobiologist Joel Heath of University College London (UCL), in England, in a statement.
He added: “The fossil record has such large gaps that it can’t be taken at face value.”
At present, the oldest known dinosaur fossils—which have been found in more southerly locales like Argentina, Brazil and Zimbabwe—date back some 230 million years.
However, the varied nature of these specimens suggests that the dinosaurs had already been evolving for millions of years before that time.
In their study, Heath and his colleagues conducted simulations to assess where the earliest dinosaurs might have evolved.
They incorporated data on the fossils and known evolutionary trees of both dinosaurs and their close reptile relatives, as well as the geography of the early Triassic.
At this time, tectonic movements had arranged most of Earth’s landmasses into two vast supercontinents: Laurasia in the north and Gondwana in the south.
The team accounted for gaps in the fossil record by regarding areas of the globe where no fossils have been found as areas of missing information, rather than areas where no such fossils exist.
“Our modeling suggests that the earliest dinosaurs might have originated in western, low-latitude Gondwana,” said Heath.
This area—what is today the Amazon, Congo basin and Sahara Desert—represents a midpoint between where some of the earliest-known dinosaurs lived in southern Gondwana and where their reptile relatives lived to the north.
Heath continued: “This is a hotter and drier environment than previously thought [for the origin of dinosaurs], made up of desert- and savannah-like areas.
“So far, no dinosaur fossils have been found in the regions of Africa and South America that once formed this part of Gondwana.
“However, this might be because researchers haven’t stumbled across the right rocks yet, due to a mix of inaccessibility and a relative lack of research efforts in these areas.”
As is perhaps to be expected, the modeling suggests that the early dinosaurs were at first vastly outnumbered by their reptile relatives.
These included the “pseudosuchians”—the ancestors of modern crocodiles, some species of which could reach nearly 33 feet long—and the iconic pterosaurs, some of whom grew to have wingspans that rivalled those of fighter jets.
In contrast, the earliest dinosaurs were much smaller, at around the size of a chicken. They walked on two legs and are thought to have been omnivores.
The dinosaurs only became dominant around 201 million years ago, when a series of volcanic eruptions from the so-called Central Atlantic Magmatic Province wiped out many of their reptile cousins.
Having evolved in western Gondwana, the researchers explain, dinosaurs spread outwards into southern Gondwana and the neighboring supercontinent Laurasia, which would eventually go on to break up into North America, Europe and Asia.
“Our results suggest early dinosaurs may have been well-adapted to hot and arid environments,” said paper author and UCL paleobiologist professor Philip Mannion in a statement.
“Out of the three dinosaur groups, one group—sauropods, which includes the Brontosaurus and the Diplodocus—seemed to retain their preference for a warm climate, keeping to Earth’s lower latitudes.
“Evidence suggests the other two groups, theropods and ornithischians, may have developed the ability to generate their own body heat some millions of years later in the Jurassic period, allowing them to thrive in colder regions—including the poles.”
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Reference
Heath, J.A., Cooper, N., Upchurch, P., & Mannion, P.D. (2025). Accounting for sampling heterogeneity suggests a low palaeolatitude origin for dinosaurs. Current Biology. http://dx.doi.org/10.1016/j.cub.2024.12.053
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