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 on Wednesday In the journal Nature Megachirella is the "mother of all lizards", the oldest known ancestor of all squamates. Its existence helps to explain the transition from more primitive reptiles to the large, diverse order that is now slithering, sneaking and digging across all continents except Antarctica.
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 a paleontologist at the University of Alberta, "in terms of the information available on the evolution of snakes and lizards"
Megachirella's partial skeleton was created by discovered by an amateur fossil hunter in the Dolomites of northern Italy and first described by scientists in 2003. But, limited by the technology of that time and an incomplete understanding of the Squamata order, researchers were not quite sure how the new species fit into the phylogenetic tree of the reptiles.
Fifteen years later, high-resolution micro-CT scanning made it possible to look into the rock that retained the tree's fossil and identify its hidden features. 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 a 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 greatly expanded dataset, it became possible to assess the relationship not only of this species but also of other species of reptiles," Simões
as Megachirella in the In the middle Triassic crossing the earth, the landmasses of Earth 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 – suggest that a strong storm hit the shoreline where Megachirella lived and swept the tiny creatures into the sea.
Simões and his colleagues are still seeking 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 a familiar 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."