Here's a fact you should know about the world in which you live: it houses more species of scaly reptiles than all the mammal families combined. The reptilian order Squamata, which includes snakes, lizards and legless worm-like creatures known as amphibians, is the largest order of living vertebrates on the planet.
And yet scientists know amazingly little about where all these geckos and vipers and iguanas are and pythons came from. Genetic evidence suggests that the order originated more than 250 million years ago in the Permian. But the oldest known sham fossil was about 70 million years younger than that.
"That's more time than between us and the dinosaurs, and we had no idea what was going on," said Tiago Simões, a paleontologist at the University of Alberta
Enter Megachirella wachtleri a three-inch, 240-million-year-old fossil ̵
According to a study by Simões and his colleagues, published Wednesday in the journal Nature, Megachirella is the "mother of all lizards", the oldest known ancestor of all shamans. Their existence explains the transition from more primitive reptiles to the large, diverse order that now slips, sneaks and digs across all continents except the Antarctic.
In a video for the MUSE Science Museum in Trento, Italy, co-author Michael Caldwell called the fossil a "perfect example".
"It's almost a virtual Rosetta stone," said Caldwell, also paleontologist at the University of Alberta, "in terms of the information available on the evolution of snakes and lizards."
Megachirella's partial skeleton was discovered by an amateur fossil hunter in the Dolomites of northern Italy and first described in 2003 by scientists. But limited by the technology of the time and an incomplete understanding of the squamate order, the researchers were not quite sure how the new species fit into the reptile tree.
Fifteen years later, high-resolution micro-CT scans allowed to scan into the fossil's rock and identify traits hidden within. At a synchrotron facility, Simões and his colleagues identified features in the animal's brain, collarbone, and wrists that are unique to lizards. They also found evidence of rudimentary features that modern squamates have since lost – a small cheekbone called Quadratore and primitive abdominal bones, called gastralia (also found in many dinosaurs).
Simões dedicated his doctoral thesis to understanding the family tree of the living and extinct dandruff.
"For the first time, when this information became available with this highly expanded dataset, it became possible to assess the relationship not only of this species but also of other reptile species," Simões said.
When Megachirella crossed Earth in the Middle Triassic, Earth's land masses were beaten up in a supercontinent called Pangea. Flowers had not developed, and the soil was dominated by primitive plants called lycopods (ancestors of lump moss and quill words). The conditions under which the fossil was found – in marine sediments but surrounded by fossilized land plants – indicate that a powerful storm hit the shoreline where Megachirella lived and set the tiny creature to sea.
Simões and his colleagues are still searching for evidence of Megachirella's behavior. And they still have to fill the tens of millions of years between Megachirella and the next oldest Sham fossil. Many fossil lizards from the early Cretaceous (more than 100 million years ago) do not seem to fit into any known lineage, and Megachirella could help explain these curiosities.
"It confirms that we are quite unaware," Simões said of the new species. " But on the positive side, we also have all this additional information regarding the transition from more general reptile traits to more lizard-like traits."
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