Scientists have identified the world's oldest lizard - the most most ancient ancestor of all modern lizards and snakes - by analysing a 240-million-year-old fossil. The study, published in the journal Nature, provides key insight into the evolution of modern lizards and snakes. The 240-million-year-old fossil, Megachirella wachtleri, is the most ancient ancestor of all modern lizards and snakes, known as squamates, according to researchers including those from the University of Bristol in the UK.
The fossil, along with data from both living and extinct reptiles - which involved anatomical data drawn from CT scans and DNA - suggests the origin of squamates is even older, taking place in the late Permian period, more than 250 million years ago. "The specimen is 75 million years older than what we thought were the oldest fossil lizards in the entire world and provides valuable information for understanding the evolution of both living and extinct squamates," said Tiago Simoes, PhD student from the University of Alberta in Canada.
Currently, there are 10,000 species of lizards and snakes around the world -- twice as many different species as mammals. Despite this modern diversity, scientists did not know much about the early stages of their evolution. "It is extraordinary when you realise you are answering long-standing questions about the origin of one of the largest groups of vertebrates on Earth," said Simoes. "Fossils are our only accurate window into the ancient past. Our new understanding of Megachirella is but a point in ancient time, but it tells us things about the evolution of lizards that we simply cannot learn from any of the 9000 or so species of lizards and snakes alive today," said Michael Caldwell, also from the University of Alberta.
Originally found in the early 2000s in the Dolomites Mountains of Northern Italy, researchers considered it an enigmatic lizard-like reptile but could not reach conclusive placement, and it ramained nearly unnoticed by the international community. In order to better understand both the anatomy of Megachirella and the earliest evolution of lizards and snakes researchers assembled the largest reptile dataset ever created.
They combined it with several new anatomical information from Megachirella obtained from high-resolution CT scans.The data was analysed using state of the art methods to assess relationships across species, revealing that the once enigmatic reptile was actually the oldest known squamate.
"At first I did not think Megachirella was a true lizard, but the empirical evidence uncovered in this study is substantial and can lead to no other conclusion," said Randall Nydam of the Midwestern University in the US.
