Friday, 19 February 2016

Fossil Hunters: Unearthing the Mystery of Life on Land...by Dave Millward and Tim Kearsey

Today sees the opening of the ‘Fossil Hunters: Unearthing the Mystery of Life on Land’ exhibition at the National Museums Scotland in Edinburgh. This event tells the story of how animals stepped out on to land for the first time about 360 million years ago. It also relates how a team of scientists discovered the evidence from rocks exposed in Scotland!

“One is accustomed these days to hear of sensational new fossil finds being made in other parts of the world. But to learn of a site in this country ..., in geological terms is wonderful and exciting.” Sir David Attenborough

Image by Mark Witton of the environment around 360 million years ago when animals stepped on to land for the first time.  
The free exhibition will be open to the public until 14th August 2016, and is the culmination of four years of scientific investigation into how and why tetrapods – vertebrates with four limbs – made the transition from water to land in early Carboniferous times. Previously, in the Devonian, 370 million years ago, tetrapods were fish-like and lived mostly in water. The next time we see them in the fossil record some 25 million years later, they were adapted fully to live on land. That hiatus in time during which no tetrapod fossils had been found became known as Romer’s Gap, after the celebrated American vertebrate palaeontologist, Alfred Romer. Many people at that time thought the gap was real and there were no fossils to be found.

The search for fossils that might occur during Romer’s Gap was begun by the late Stan Wood, a Scottish fossil hunter and owner of Edinburgh’s Mr Wood’s Fossil Shop, and Dr Tim Smithson of Cambridge University. After more than 20 years, they began to find specimens at two localities in the Scottish Borders. This confirms that Romer’s Gap was simply a gap in fossil collecting and key fossils were waiting to be found right here in Scotland. These finds were the catalyst for the start of the TW:eed Project (Tetrapod World: early evolution and diversification) funded by the Natural Environment Research Council. The team is led by Professor Jenny Clack and includes scientists from the Universities of Cambridge, Leicester, Southampton, the National Museums Scotland and the British Geological Survey.
A reconstruction of 'Ribbo' by Karen Carr.
'Ribbo' is a small tetrapod found within Romer's Gap.

Over the past 4 years hundreds of fossil-bearing rocks have been collected and processed, a 500m-deep borehole drilled and thousands of samples analysed in detail. A river has also been partially dammed to excavate fossil-bearing strata in the bed. During this project the team has found many more new tetrapods species within Romer’s Gap in Scotland to demonstrate that a remarkable diversity of species existed at that time. Most striking of the finds was a tetrapod found by Ben Otto and Ket Smithson, a masters and PhD student respectively at the University of Cambridge. They discovered a very small tetrapod skull and other bones completely encased in the rock using CAT scans.

Along with colleagues from Leicester and Southampton universities, the BGS team has sought to understand the environment in which these tetrapods lived, and how it changed through time. This may help to explain why they came on to land, rather than just how. The tetrapods were living in a world very different from the cold, windswept conditions experienced in northern Britain today. In the early Carboniferous, the UK was 4° south of the equator with a landscape that would have superficially looked like the Florida everglades. However, if you were on a boat trip through the lakes and creeks of the vast coastal plain the landscape would have appeared very alien. There were no grasses and no flowering plants at that time, but instead the ground was covered with bizarre plants like Oxroadia, affectionately called the ‘creeping toilet brush’. We also know that the climate was very seasonal, with contrasting wet and dry periods. Flooding of the coastal landscape was commonplace. It is possible that the wide range of habitats present and the climate pattern may have been factors that allowed tetrapods to adapt to the terrestrial environment and thrive.

The TW:eed project team at the launch of "Fossil Hunters" at the National Museums Scotland. 
The exhibit now at the National Museums Scotland gives everyone the chance to experience a world very different from our own. These earliest terrestrial tetrapods shed light on a crucial event in the evolution of life on Earth. If this had not occurred, we would not be here today.

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