The Origin of Lizards – GreenReport: Ecological Economy and Sustainable Development

Discovery of a fossil in Scotland offers new insight into the early evolution of lizards, when dinosaurs still existed

[28 Ottobre 2022]

A small skeleton only 6 cm long was discovered on the Scottish Isle of Skye bellarsia gracilis Which dates back to the Middle Jurassic 166 million years ago and is a truly extraordinary fossil: an almost complete skeleton with a joint similar to a natural one. It is the most complete ancient fossil lizard of that era found anywhere in the world. really, belarusia It contains a skeleton that includes a mix of ancestral and modern features and describes what the ancestors of today’s lizards, which are part of the larger group of squamates, would have looked like. The fossil was found in 2016 by a team led by the University of Oxford and the National Museum of Scotland and is one of several new fossil discoveries made on Skye, including the first amphibians and mammals, revealing the evolution of important animal groups. Huh. exist today.

Squamates are a living group that includes lizards and snakes and now include over 10,000 species, making them one of the most species-rich groups of living vertebrate animals. These include diverse animals such as snakes, chameleons and geckos, which live all over the world. The group is characterized by a number of distinctive features of the skull and the rest of the skeleton.

The results of the research were disclosed in a joint project between researchers from the Universities of Warsaw, Oxford and University College London (UCL). study Published on “Synchrotron tomography of a stem lizard elucidates early squamate anatomy” Nature, The lead author, Mateusz Talanda (University of Warsaw and UCL), stressed that “this small fossil allows us to see evolution in action. It is important to work with such complete and well-preserved fossils from an era in paleontology.” opportunity is rarely found, about which very little is known. belarusia It has some modern lizard-like characteristics, such as a trait related to cranial chiasm: it is the movement of the bones of the skull in relation to each other. It is an important functional feature of many living squamates.

At UCL he says: “Although we know that squamates first originated in the Triassic 240 million years ago, the paucity of fossils from the Triassic and Jurassic periods made it difficult to trace their early evolution and anatomy. Analysis of new fossil with extinct fossil scales confirms that belarusia It belongs to the “stem” of the family tree of Squamata. This means that it diverged from other lizards shortly before the origin of modern groups. The research also supports the finding that geckos are a very early branching lineage and are enigmatic fossils. Oculudentavis, First suggested as a dinosaur, it is a stem of Squamata.

The fossil was discovered by study co-author Elsa Panciroli of the Oxford University Museum of Natural History and the National Museum of Scotland, who recalls: “When I started working on Skye it was one of the first fossils. The skull came out of light limestone, but it was so small that I was lucky to find it. Taking a closer look I saw tiny denticles and realized I had found something important, but it wasn’t until much later that we got to know about it. Didn’t realize that almost the entire skeleton is there.

To study the sample, the team used X-ray computed tomography (CT), which, like medical CT, allows for non-invasive 3D imaging. This allowed the researchers to see the entire fossil, even though most of the specimen is still hidden by the surrounding rock. While medical scanners operate on a millimeter scale, University of Oxford CT scanners reveal details down to a few tens of micrometres. At the European Synchrotron (ESRF, Grenoble, France) parts of the skeleton were captured in even greater detail, including the skull, hind limbs and pelvis. The intensity of the synchrotron beam allows a resolution of 4 micrometers, revealing the details of the smallest bones of the skeleton.

Another study author, Roger Benson of the Department of Earth Sciences at the University of Oxford, pointed out that ‘fossils are like this specimen’ belarusia They are very important in our understanding of evolution and filling gaps in the history of life on Earth. In the past it was nearly impossible to study such small fossils, but this study shows the power of new techniques, including CT scanning, to visualize them catastrophically and in great detail.’

UCL co-author Susan Evans, who was the first to describe and name belarusia Starting with some jaw and skull bones found in Oxfordshire 25 years ago, he concluded: ‘It’s wonderful to have a complete specimen of this fascinating little lizard and see where it fits into the evolutionary tree. like through fossils belarusia We are gaining a better understanding of the anatomy of early lizards. Angus Belairs, lizard embryologist from whom it was originally belarusia If he had taken the name, he would have been happy.