How life first walked on land: Four-legged fossils found in Scotland may help fill a 15-MILLION-year gap in evolutionary history

Researchers discovered the fossils of five new species in the Scottish Borders
They come from a crucial point when amphibians split from the group that would later give rise to mammals, birds and reptiles
The only other fossils from this time have been found in Canada

Published: 13:59 EST, 5 December 2016 | Updated: 15:31 EST, 5 December 2016

e-mail

View
comments

While much is known about our evolutionary history, until now, a 15-million-year gap has remained in the fossil record.

But researchers believe they may have helped bridged that gap after unearthing five new species of what may be the earliest four-legged backboned animals to walk on land.

The animals come from a crucial point in history, when amphibians split from the group that would later give rise to mammals, birds and reptiles.

While much is known about our evolutionary history, until now, a 15-million-year gap has remained in the fossil record. But researchers have unearthed five new species in the Scottish Borders that could help to close this gap

WHY ARE FOSSILS FROM THE TIME SO RARE?

Fossils from this time are very rare, and until now, only small bones have been found in Scotland and Canada.

The reason for the gap in tetrapod data has been a hotly debated topic.

Some theories suggest that a lack of oxygen during the time led to a decrease in tetrapod numbers.

But the Cambridge researchers also analysed the oxygen in the fossils, and concluded that levels were about the same in the Tournaisian period as the later Devonian.

Researchers from the University Museum of Zoology Cambridge describe five new species of four-legged vertebrates discovered in Scotland in their paper, published in Nature Ecology and Evolution.

Some of the fossils look like lizards or newts, while others are larger, according to a report in the BBC.

'We're lifting the lid on a key part of the evolutionary story of life on land," said Prof Jennifer Clack of the University of Cambridge told the BBC.

'What happened then affects everything that happens subsequently - so it affects the fact that we are here and which other animals live with us today.'

A Perittodus apsconditus was discovered with two tusks and at least two smaller teeth, pictured bottom row, while a Koilops herma was found to have fine irregular teeth, pictured top row

Around 360 million years ago, four-legged vertebrates, known as tetrapods, split into two groups – the ancestors of amphibians, and the ancestors of amniotes (mammals, birds and reptiles).

But fossils from this time are very rare, and until now, only small bones have been found in Scotland and Canada.

The reason for the gap in tetrapod data has been a hotly debated topic.

Some theories suggest that a lack of oxygen during the time led to a decrease in tetrapod numbers.

One of the fossils was a lower jaw with an unusual double row of teeth, which the researchers named Diploradus austiumensis

The Ossirarus kierani fossil had an estimated skull length of 50mm, and the researchers say the structure suggests the animal was not a juvenile when it died

But the Cambridge researchers also analysed the oxygen in the fossils, and concluded that levels were about the same in the Tournaisian period as the later Devonian.

The researchers discovered the fossils in ancient rock in the Scottish Borders, dating back to the Tournaisian period.

The fossils suggest that the first backboned animals on land may have lived in the Scottish Borders

They latest fossils suggest that the first backboned animals to crawl around on land may have lived in what is now Scotland.

Two of the fossils belong to early amphibians, and resemble small lizards, while the other three belong to amniotes.

One of the fossils was a lower jaw with an unusual double row of teeth, which the researchers named Diploradus austiumensis.

Another was a partial skull of a short-snouted animal with slender limbs, called Aytonerpeton microps.

Speaking to the BBC, Professor Jennifer Clack, who led the study, said: 'We're lifting the lid on a key part of the evolutionary story of life on land.

'What happened then affects everything that happens subsequently - so it affects the fact that we are here and which other animals live with us today.'

The fossils suggest that the first backboned animals on land may have lived in the Scottish Borders, or that similar fossils in other areas haven't been found yet.