Analysis of 231-million-year-old fossil sheds light on evolution of reptiles – Harvard Gazette

The Lepidosaurus fossil was not just any Lepidosaurus, but the first member of this group that evolved apart from the rest. This places him at the top of that lineage and provides key evidence of how lizards first evolved from more primitive reptiles. This kind of respect is shown in the name scientists have chosen for it: Taytalura alcoberi, meaning father of lizards in the Quechua and Kakán languages ​​of the Andean people originally from Argentina.

Taytalura is the oldest evolving Lepidosaurus, but it is not the oldest Lepidosaurus fossil ever to be found. This honor belongs to a 242 million year old squamate and a 234 million year old sphenodontian. This suggests an older Taytalura Maybe one day a fossil will be found.

Either way, the age difference shows that these very early Lepidosaurs lived side by side with squamates and sphenodonts, known as “true” Lepidosaurs, for at least 10 million years over the course of time. from the Triassic period, a fact hitherto unknown.

The researchers used three-dimensional CT scans of the preserved head to analyze the fossil. This allowed them to compare this early Lepidosaurian skull with Lepidosaurus and other later reptiles. Researchers, for example, noticed that the skulls of early Lepidosaurs looked much more like those of sphenodontians than those of squamates, and that the squamates represent a major deviation from older skull models. They also found Taytalura the teeth differed from those of any living or extinct Lepidosaurus group.

Another surprising discovery concerned the location where the fossil was found. Until now, almost all the fossils of the Triassic Lepidosaurs have been found in Europe. It is the first primitive lepidosaurus found in South America. This suggests that Lepidosaurs may have migrated across the planet (then only one supercontinent) very early in their evolutionary history.

This 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 that it could likely 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 on the planet, Simões said. “[It] was probably the prey of some of the first dinosaurs to walk on Earth, ”he said.

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CT scans of crocodile skulls.

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 the entire group was born, which will be essential to understanding the long evolutionary history of reptiles in order to help those that exist today.

“Lepidosaurs have survived three of the five great mass extinctions in Earth’s history over the past 260 million years,” said Simões. “By accurately reconstructing the long evolutionary history of Lepidosaurus, we may be able to tell in much greater detail how they survived and thrived successfully through the major environmental changes of Earth’s past and how they may be affected by the modern human-induced climate change. “

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