Analysis of 231-million-year-old fossil sheds light on reptile evolution

September 01, 2021

The lepidosaur fossil was not just any lepidosaur, but the first member of this group that evolved away from the others.Taytalura is the earliest evolving lepidosaur, but it is not the oldest lepidosaur fossil ever found.That suggests an older Taytalura fossil may one day be found.This is the first early lepidosaur found in South America.It suggests lepidosaurs were able to migrate across the planet (which then was all still one supercontinent) very early in their evolutionary history.

The lepidosaur fossil was not just any lepidosaur, but the first member of this group that evolved away from the others. That puts it at the top of that lineage and provides key evidence of how lizards first evolved from more primitive reptiles. That kind of respect is shown in the name the scientists chose for it: Taytalura alcoberi, meaning father of the lizards in the Quechua and Kakán languages of the native Andean people of Argentina.

Taytalura is the earliest evolving lepidosaur, but it is not the oldest lepidosaur fossil ever found. That honor belongs to a 242 million-year-old squamate and a 234 million-year-old sphenodontian. That suggests an older Taytalura fossil may one day be found.

Regardless, the age discrepancy shows that these very early lepidosaurs lived side by side with squamates and sphenodontians, known as “true” lepidosaurs, for at least 10 million years during the Triassic period, a fact that was previously unknown.

The researchers used micro-CT scans of the three-dimensionally preserved head to analyze the fossil. It allowed them to compare this early lepidosaurian skull with later lepidosaur and other reptiles. The researchers, for instance, noticed that the skull of the first lepidosaurs looked substantially more like those of sphenodontians than squamates and that squamates represent a major deviation from the older skull patterns. They also found Taytalura teeth differed from those in any living or extinct group of lepidosaurs.

Another surprising finding involved where the fossil was discovered. Till now, almost all fossils of Triassic lepidosaurs have been found in Europe. This is the first early lepidosaur found in South America. It suggests lepidosaurs were able to migrate across the planet (which then was all still one supercontinent) very early in their evolutionary history.

That type of mileage is impressive for such a small creature. While it’s impossible to accurately estimate the total body length of this lizard-like reptile, the one-inch head suggests it likely could fit in the palm of a human hand. The creature most likely fed on insects from desert environments that it shared with some of the oldest dinosaurs in the planet, said Simões. “[It] was most likely preyed upon by some of the first dinosaurs to walk on Earth,” he said.

The researchers hope to explore older rocks in Argentina or other parts of South America and find older members of this lineage. The hope is to determine the exact time when the entire group originated, which will be critical in understanding the long evolutionary history of reptiles to help those that exist today.

“Lepidosaurs survived across three out of the five big mass extinctions on Earth’s history during the last 260 million years,” Simões said. “By accurately reconstructing the long evolutionary history of lepidosaurs, we may be able to tell in much greater detail how they successfully survived and flourished across major environmental shifts in Earth’s past and how they may be impacted by modern human-induced climate change.”

The source of this news is from Harvard University

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