Edinburgh, Fife & East Scotland

Fossils 'solve' missing evolutionary link mystery

Fossil Hunters: Unearthing the Mystery of Life on Land Image copyright Phil Wilkinson
Image caption Experts have said the fossil finds are "pivotal" to understanding evolution

Scottish fossils that appear to solve the mystery of how vertebrate life came to move from water to land will go on display in an exhibition in Edinburgh.

The fossils were found in the Borders and date from a missing period in geological history between 360 and 345 million years ago.

Scientists said the find was pivotal to our understanding of evolution.

The National Museum of Scotland exhibition, which opens on Friday, runs until Sunday 14 August.

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Media captionFossil of one of the earliest animals to walk on land on display at the National Museum of Scotland

The exhibition, Fossil Hunters: Unearthing the Mystery of Life on Land, is free ti visitors.

The fossils were found over the past few years - some as recently as summer 2015 - and have been at the National Museums Collections Centre in Edinburgh until now.

Until recently, there was very little fossil evidence of life on land during the early Carboniferous period, around 345-360 million years ago.

Image copyright National Museums Scotland
Image caption Westlothiana , one of the earliest known reptiles

It was in this period that vertebrate life moved from the sea to the land.

The 15-million-year missing link is named "Romer's Gap" after the American palaeontologist Alfred Sherwood Romer, who identified it.

Some palaeontologists concluded that low levels of oxygen during this period restricted evolution on land.

However, experts said these fossils confirm that a rich and diverse ecosystem of amphibians, plants, fish and invertebrates thrived during this period.

Image copyright Karen Carr
Image caption Reconstruction of Ribbo, a tetrapod from Romers Gap

One of palaeontology's unanswered questions, that of how vertebrate life crawled out of the water, will also be addressed.

Visitors to the exhibition will have the opportunity to discover how amphibians took their first steps on to land and why it is such an important milestone in the evolutionary timeline.

They will also be able to find out about the techniques used to unearth the fossils and what the analysis of the finds tell about life on land before the dinosaurs.

Long before vertebrates evolved legs, there was already life on land.

The earliest-known terrestrial ecosystem in the world is preserved in a bed of sediment in Aberdeenshire called Rhynie Chert.

The 410-million-year-old rock contains plants, spiders and the oldest-known fossil insects.

However, there was no evidence of tetrapods (vertebrates with four limbs) on land.

Fossil evidence pre-dating Romer's Gap showed tetrapods living in the water 360 million years ago, but their limbs were not strong enough to support them on land.

Around 15 million years later, evidence of tetrapod life on land can be found, by which point amphibians were well-adapted to walking.

Palaeontologists could only speculate as to how and why the monumental step from water to land was taken.

Image copyright Karen Carr
Image caption Reconstruction of Westlothiana , one of the earliest known reptiles and also called 'Lizzie'

The late Stan Wood, a self-taught Scottish field palaeontologist, was convinced that fossil evidence of tetrapod life during Romer's Gap could be found in Scotland, and spent 20 years searching for it.

In 2011, he uncovered never-before-seen fossil evidence of early tetrapod life on land - fossil animal skeletons, along with millipedes, scorpions and plants- at the Whiteadder River, near Chirnside.

Image copyright Maggie Wood
Image caption The late Stan Wood coming out of the water with a fossil

Nick Fraser, keeper of natural sciences at National Museums Scotland said: "National Museums Scotland holds one of the finest collections of fossils of early, land-based life in the world.

"Solving the mystery of this evolutionary missing link is hugely exciting, and has allowed us to gain a rich understanding of a key period in the evolution of life on earth.

"This fascinating exhibition will explore in detail for the first time the full story of this remarkable discovery."

Long before vertebrates evolved legs, there was already life on land.

Image copyright National Museums Scotland
Image caption Fossil millipede, Diplopoda, in two parts, from the Romer's Gap. Discovered in Willie's Hole, Whiteadder Water, Berwickshire
Image copyright Mark Witton
Image caption Artist's impression of underwater environment of Carboniferous swamp depicting a rhizodont
Image copyright Phil Wilkinson
Image caption The National Museum of Scotland exhibition, which opens on Friday, runs until Sunday 14 August

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