If dinosaurs really did appear near the equator, life would have been particularly hot and dry.
Mark Whitton/Natural History Museum Trustees
Dinosaurs may have first evolved near the equator, rather than far south in the Southern Hemisphere as previously thought. Modeling studies suggest they originated in areas covering what is now the Amazon rainforest, the Congo Basin, and the Sahara Desert.
“Given the gaps in the fossil record and the evolutionary tree of dinosaurs, it is very likely that this is the central point of dinosaur origin,” he says. Joel Heath At University College London.
Dinosaurs evolved during the Triassic period, which lasted from 252 million to 201 million years ago, but there is “considerable” uncertainty about when and where they evolved, Heath said. The oldest known fossils of these animals are about 230 million years old, but there are enough features to suggest that dinosaurs have already been around for millions of years. “There must have been a lot going on in terms of dinosaur evolution, but we don't have the fossils,” he says.
At this time, the Earth looked very different. All the continents were combined into a single supercontinent called Pangea, shaped like a C with its center straddling the equator. South America and Africa were located in this southern hemisphere part and were fitted together like pieces of a jigsaw puzzle. The earliest known dinosaurs lived in the southern parts of these two continents, in present-day Argentina and Zimbabwe, where dinosaurs were thought to have originated.
To learn more, Heath and his colleagues built a computer model that works backwards in time from the oldest known dinosaurs to the group's origins. They considered uncertainties such as gaps in the fossil record, possible geographic barriers, and ongoing questions about how the earliest dinosaurs were related to each other to create dozens of versions. has been created.
Most of these simulations concluded that dinosaurs first appeared near the equator, with only a few supporting a southern origin.
Paleontologists have tended to believe that dinosaurs couldn't have originated near the equator, Heath said. One reason for this is that no early dinosaur fossils have been found in the area. Moreover, it was a difficult place to live. “It was very, very dry and very hot,” he says. “It is believed that dinosaurs could not have survived in such conditions.”
However, most models do not. “This suggests something that we didn't really think was possible until now,” Heath says.
In fact, there may be a more prosaic explanation for the lack of early dinosaur fossils found near the equator. Paleontologists tend to conduct excavations in North America, Europe, and more recently China. “There are many areas of the planet that are completely ignored,” says Heath. He added that geologists have not found many rocks of suitable age in the area associated with the findings that can be excavated. “It may not be exposed in a way that we can easily investigate.”
But evidence supporting Heath's idea has recently come to light. On January 8th, researchers david loveless At the University of Wisconsin-Madison, oldest known dinosaur Originally from northern Pangea. They discovered what they call a species new to science. Avaitum Banduiche, sauropodomorphs related to long-necked dinosaurs such as diplodocus That evolved later. The research team discovered the 230-million-year-old rock in Wyoming's Popo Aggie Formation.
If dinosaurs were already present north and south of Pangea that long ago, there's no way the middle of the equator would be closed off to them, Heath said. “They must have been crossing the area.”
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Source: www.newscientist.com
