Life would have been particularly hot and dry if dinosaurs really did originate near the equator
Mark Witton/The Trustees of the Natural History Museum, London
Dinosaurs first evolved close to the equator, not in the far south of the southern hemisphere as previously thought. A modeling study suggests that they originated in a region that includes what is now the Amazon rainforest, the Congo basin, and the Sahara desert.
“When you take into account the gaps in the fossil record and the evolutionary tree of dinosaurs, it’s very likely that the dinosaurs originated somewhere in the middle,” he says. Joel Heath at University College London.
Dinosaurs It evolved during the Triassic period between 252 and 201 million years ago, but Heath says there is “fairly large” uncertainty about where and when. The best-known fossils of these animals are about 230 million years old, but they are different enough to suggest that dinosaurs were already around a few million years ago. “There must have been a lot in terms of dinosaur evolution, but we don’t have fossils,” he says.
At this time, the Earth looked very different. All the continents were united in a single supercontinent called Pangea, which was shaped like a C, with the center on the equator. South America and Africa were in the southern hemisphere segment of this, where they fit together like puzzle pieces. The first known dinosaurs are from the south of these two continents, in places like today’s Argentina and Zimbabwe; so this was believed to be their origin.
To learn more, Heath and his colleagues built computer models to work backwards in time from the oldest known dinosaurs to the origins of the group. They created a dozen versions to account for gaps in the fossil record, possible geographic barriers, and questions about how the early dinosaurs were related.
Most of these simulations concluded that dinosaurs first appeared near the equator, with a minority supporting a southern origin.
Paleontologists have long believed that dinosaurs could not have originated near the equator, Heath says, in part because there are no early dinosaurs. the fossils from that region. Moreover, it was a difficult place to live. “It was very, very dry and very hot,” he says. “They thought dinosaurs couldn’t survive in those conditions.”
However, most models suggest otherwise. “It’s suggesting things that we didn’t really think were possible in the past,” says Heath.
Instead, the lack of early dinosaur fossils near the equator may have a more prosaic explanation. Paleontologists have tended to dig in North America and Europe, and more recently in China. “There are a lot of areas in the world that are pretty neglected,” says Heath. He added that geologists have not found many rocks of the right age that they can excavate in the regions relevant to the research findings. “They may not be exposed in a way that can be investigated.”
However, recently a piece of evidence has emerged in support of Heath’s idea. On January 8, the researchers directed David Lovelace The discovery was reported at the University of Wisconsin-Madison the oldest known dinosaur From the north of Pangea. They discovered a species that is new to science Ahvaytum bahndooiveche, a sauropodomorph related to long-necked dinosaurs such as Diplodocus which evolved later. The team found it in 230-million-year-old rocks from the Popo Agie Formation in Wyoming.
If dinosaurs existed north and south of Pangea a long time ago, the middle of the equator cannot be closed to them, says Heath. “They must be crossing that region.”
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