Wednesday, 26 September 2012

BGS Open Day Showcases new tetrapod finds


On Saturday 22nd September the British Geological Survey’s (BGS) office in Edinburgh was opened to the public as part of Edinburgh’s Doors Open Day. This event, held annually, had the theme of ‘hidden treasures’. There were plenty of these to seek out as the BGS was packed with Earth science demonstrations, talks, experiments and displays of work undertaken at home and abroad. There were lots of hands-on activities to interest people of all ages, some 750 of whom came through the doors.

TWeed Project members Nick Fraser (National Museum of Scotland) and Dave Millward (BGS) were on hand to talk about the display of fossils collected by Stan Wood from the Scottish Borders. These are just a few of the many specimens already collected and which will form the heart of our investigations. An accompanying poster explained the significance of Romer’s Gap and set the context for these extraordinary and unique finds. The exhibition included not only tetrapod material but examples of fish, shrimps, millipedes and a scorpion. The display attracted a lot of interest and questions from visitors, including some from the Borders area. Offers of help were gratefully received and many indicated that they would be back next year for an update! Copies of the project newsletter were given out along with information on how to find this Blog. If you would like to receive copies of the newsletter (as a PDF or paper copy), please email me at info@tetrapodworld.com. And check the BGS website for news of future open days and events.

Top: Nick Fraser (National Museum of Scotland) and Dave Millward (BGS) talking to an interested visitor. Bottom: limb bones from an early amphibian – an example of the superbly preserved materials from Stan Wood’s collections.


What is the significance of the new fossils?

This is some very useful information from the poster that gives an overview of the project:

What is Romer’s Gap?
When did limbed vertebrates - or tetrapods - adapt to walk on land? How long and under what circumstances did it take to achieve this? These are key questions that shaped the future evolution of life on Earth, including the eventual appearance of humans. The process began about 360 million years ago at the end of Devonian times when a mass extinction event changed the world for ever. Many fish groups became extinct and their place was taken by modern forms. Modern plant groups, including true ferns and seed plants, diversified. Before the mass extinction tetrapods were essentially aquatic and fishlike, but afterwards they emerged on to land for the first time. The animals seen later in the Carboniferous around 340 million years ago very strongly resemble modern forms.

Until now, the intervening 20 million years has remained almost unrepresented for fossil tetrapods. Thus, we know little about how they evolved adaptations for life on land, the environments in which they did so, and the timing or sequence of these events. The evolutionary relationships among these early tetrapods and how they relate to modern forms are also unclear and controversial as a result of this lack of fossil information. The entire fossil hiatus has been called 'Romer’s Gap' after the American palaeontologist who first recognized it.

            New tetrapod fossils

Now, for the first time anywhere in the world, new fossil localities that lie within Romer’s Gap have been found in south-eastern Scotland. These have already provided a wealth of new fossils of tetrapods, fish, invertebrates and plants. During the next 4 years the TWeed project team will be the first to have the opportunity to study these specimens and to search for others. Team members will also investigate the environmental, depositional, and climatic context in which this momentous episode took place.

            The Early Tetrapod World

The fossils are all from the Ballagan Formation, a distinctive rock unit that crops out widely across the Midland Valley of Scotland, East Lothian and the Borders through into Northumberland. The Ballagan Formation is a cyclic succession of mudstone, with interbedded sandstone and thin beds and nodules of 'cementstone'. These rocks were deposited on an extensive, low relief, muddy floodplain that was traversed by meandering streams flowing from the north and north-east. Periodically, the river-derived floods submerged the floodplains generating extensive shallow freshwater floodplain lakes including some that were more permanent. The widespread presence of gypsum and pseudomorphs after halite, particularly in the Midland Valley of Scotland, suggests that these were marginal marine coastal floodplains that were subject to occasional marine transgressions and fluctuating salinity.

Project aspirations

The collaborative nature and efforts of our team, with its wide range of experience and expertise can, for the first time anywhere in the world:
• Provide a coherent picture of the biological, environmental and geological conditions during the 15-20 million years recovery period following the mass extinction event at the end of Devonian times.
• Explore and explain the changes during this period that laid the foundations for the emergence of modern fauna and flora, and when tetrapods underwent a major radiation into diverse groups including predominantly terrestrial forms for the first time.
• South-east Scotland is the only place so far known in the world where we can obtain this quality and depth of data to understand a crucial period of Earth history: it is of international significance.

Until next time
Carys

Monday, 24 September 2012

How Science Works: from mud to microfossils


This week I have been sieving mud! But it’s not as boring as it sounds, far from it, as the mud contains thousands of tiny microfossils. When larger fossils (such as tetrapods) are hard to find, the sediment itself can house thousands of tiny fossil fragments that can give you a great deal of information. The sample I examined contained tiny plant fossils (roots, stem, leaves and spores), ostracods, arthropod cuticle, fish teeth and bones and vertebrate bones (that may have come from a tetrapod, hard to say when they are so small). The pieces ranged in size from 2mm to 0.1mm, but the finer your sieve, the smaller the fossils you see.

So how do you turn a mud rock into microfossils? These are the basics.

Step 1. Break up your mudrock into small pieces with your fingers. If the rock does not break up easily you should seek advice on how to break it down with acid, for which you will need professional safety kit (fume cupboard etc.), so you will need to work in a certified laboratory such as at a university. But if you have soft muds you can just use water and do it at home.
 
Step 2. Sieve the pieces with water through at least 2 sieves stacked on top of each other. Put the largest sieve holes at the top, I like to use the following sizes as a minimum: 0.125mm, 0.425mm and 1mm to catch any larger rock bits that remain. Make sure you sieve them into a sink where muddy grit drainage will not cause a problem!

Step 3. When the water runs clear from the sieve you can collect the residue. Put what remains in each sieve into filter paper or small containers (keeping each size fraction separate). This is a tricky bit, as you need to tilt each sieve to wash the pieces into a heap before you can tip them into the container. A small hose pipe attached to a tap is very useful here. Leave the samples to dry.

Step 4. Pick through the residues under a microscope. Put a small amount of residue on a picking tray and examine it at a high enough magnification so you can see what the pieces are made of. Below is me picking under the microscope and a close up of the picking tray and slide equipment that I use.

Step5. Using a paintbrush pick out specimens you are interested in and put them in a slide for further study. Below are close-up photos of the cells of the slide, containing 1-2) vertebrate microfossils and 3-4) plant microfossils.



If you want to try this yourself you can purchase sieves from a geological supply company (online) and use a magnifying lens (or hand lens) instead of a microscope.
Want to know more about micropalaeontology?

The Natural History Museum in London has an excellent blog written by their Curator of Micropalaeontology Dr Giles Miller.

Until next time
Carys