Oldest existing lizard-like fossil discovered

The fossilised remains of a reptile closely related to lizards are the oldest yet to be discovered, scientists say.

Updated: Sep 25, 2013, 20:46 PM IST

Berlin: The fossilised remains of a reptile closely related to lizards are the oldest yet to be discovered, scientists say.

Two new fossil jaws discovered in Vellberg, Germany provide the first direct evidence that the ancestors of lizards, snakes and tuatara - known collectively as lepidosaurs - were alive during the Middle Triassic period - around 240 million years ago.

The new fossil finds predate all other lepidosaur records by 12 million years.

The international team of scientists who dated the fossil jaws have provided evidence that lepidosaurs first appeared after the end-Permian mass extinction event, a period when fauna began to recover and thrive in the more humid climate.

"The Middle Triassic represents a time when the world has recovered from the Permian mass extinction but is not yet dominated by dinosaurs. This is also when familiar groups, such as frogs and lizards, may have first appeared," lead author Dr Marc Jones, who conducted the research at University College London (UCL) said.

The small teeth and lightly built jaws suggest that the extinct animal preyed on small insects. The new fossils are most closely related to the tuatara, a lizard-like reptile.

Tuatara can be found on 35 islands lying off the coast of New Zealand and were recently reintroduced to the mainland. However, they are the sole survivors of a group that was once as globally widespread as lizards are today.

To establish the age of the fossil remains, biologists use a dating technique known as a "molecular clock."

This method compares the amount of genetic divergence between living animals, caused by changes in their DNA sequences that have accumulated since they split from a common ancestor.

These mutations occur fairly regularly, ticking along at a clock-like rate.

Molecular clocks have been used by biologists to answer questions as important as when the first modern humans emerged, and when humans and chimpanzees shared a common ancestor.

The new fossil jaws can improve molecular dating estimates of when reptiles began to diversify into snakes, lizard and tuatara, and when the first modern lizards inhabited the Earth.

Previous estimates have varied over a range of 64 million years and the team are keen to help narrow this down.

"Some previous estimates based on molecular data suggested that lizards first evolved 290 million years ago," said second author Cajsa Lisa Anderson, University of Gothenburg.

The study was published in journal BMC Evolutionary Biology.