Megachirella wachtleri is the oldest known ancestor of snakes and lizards

Megachirella Wachtleri (Photo courtesy MUSE - Science Museum, Trento, Italy)
Megachirella Wachtleri (Photo courtesy MUSE – Science Museum, Trento, Italy)

An article published in the journal “Nature” describes a research on Megachirella wachtleri, a reptile that lived about 240 million years ago of which a fossil skeleton was discovered in the Dolomites Mountains of Northern Italy. A team of researchers examined the remains of this animal concluding that it’s the oldest known ancestor of modern squamates, the taxonomic order that includes lizards, snakes and amphisbaenians.

Megachirella wachtleri was a small animal probably no longer than 15 centimeters (6 inches) with a slightly elongated neck and forelegs that were very large and strong compared to its body. The first examinations of the partial skeleton discovered in the Dolomites and described in 2003 led to the hypothesis that it was related to lizards but a part of the bones was impossible to extract from the rock and this prevented from studying it completely.

This is a typical case in the field of paleontology and in recent years various technologies have been helping scientists solve the problem. The Megachirella wachtleri fossils were submitted to a X-ray microtomography, a kind of CT scan adapted to study ancient organisms instead of living beings. This type of examination allows to create a high-definition 3D reproduction of the skeleton, which is completely separate from the surrounding rock.

This was only the first part of the study because then the researchers compared the anatomy of Megachirella wachtleri’s virtual version with that of over 130 lizards and snakes worldwide. The authors used both fossils and live specimens performing exams, sometimes more X-ray microtomography, taking photos and molecular analyzes. It was a long and complex work that allowed to better understand the relationships among the various species and especially with Megachirella wachtleri.

The researchers’ conclusion is that Megachirella wachtleri is the oldest known squamate. The origin of this taxonomic order, one of the most diversified among tetrapods along with birds, has been a source of discussion and so far the oldest known representative of that group was a fossil dating back to the Middle Jurassic, about 168 million years ago.

This means that squamates emerged much earlier, an important element also because it places their origin in the Permian period, before the greatest mass extinction of the history of life on Earth that marked the end of that geological period. This is a really important progress in understanding the evolution of squamates.

Dr. Massimo Bernardi of MUSE Science Museum, Italy and University of Bristol’s School of Earth Science, pointed out the importance of using new technologies to study specimens already known, sometimes for a long time. This is not an isolated case in the field of paleontology, on the contrary it’s one of many in which fossils discovered sometimes decades before get studied again. It’s for this reason that Dr. Bernardi also reminded of the importance of preserving the specimens available in collections that are well maintained and publicly accessible.

Megachirella Wachtleri reconstruction (Image courtesy Davide Bonadonna)
Megachirella Wachtleri reconstruction (Image courtesy Davide Bonadonna)

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