Middle Jurassic fossil clarifies lizard evolution

(ORDO NEWS) — Experts studied the skeleton of a Middle Jurassic lizard found on the Scottish Isle of Skye. The new information fills in gaps in data on the evolutionary development of squamates.

Scaly is a detachment of reptiles, which include lizards and snakes. Today it has more than 10 thousand species, which makes it one of the largest groups of vertebrates.

Representatives of the order are, for example, chameleons and geckos, iguanas and monitor lizards. The scaly ones arose in the Triassic period about 240 million years ago, but so far scientists have not been able to find fossils from this period.

This did not allow specialists to trace the process of evolution of the representatives of the detachment at the stage of emergence.

In 2016, a team of paleontologists found a new fossil on the Scottish Isle of Skye. In this place, scientists have already managed to discover a number of fossils of the Middle Jurassic period.

They shed light on the evolution of stegosaurs and other ancient animals, including tyrannosaurs. The skeleton found in the fossil belongs to a lizard named Bellairsia gracili.

She lived 166 million years ago, and her size is only six centimeters in length. It is the most complete fossil of a lizard of this age found to date, showing all articulations and missing only the edge of the snout and tail.

To study the sample, experts used computed tomography. With its help, the researchers obtained an image of the entire fossil, although most of the sample was hidden by the surrounding rock. Details scientists were able to identify with an accuracy of several tens of micrometers.

The authors then studied the samples using the ESRF synchrotron in France. So they got even more detailed images with a resolution of 4 micrometers.

The analysis showed that Bellairsia gracili has some features of modern lizards. For example, the movement of the bones of the skull relative to each other.

This is an important functional feature of most squamates. Bellairsia gracili diverged from other lizards shortly before the emergence of modern groups.

The study also supports the conclusion that geckos are a very early group and that the mysterious fossil Oculudentavis, previously found and thought to be a dinosaur, is in fact also scaly.

“Fossils like Bellairsia gracili are of great value in filling gaps in our understanding of the evolution and history of life on Earth.

Previously, it was almost impossible to study such tiny fossils, but this study shows the power of new methods, including computed tomography, to image them in great detail,” said study co-author Roger Benson of the University of Oxford.


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