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Curator of Micropalaeontology's blog

5 Posts tagged with the cretaceous tag
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It feels strange recommending readers to go to another museum. However, this is a great example of the application of Micropalaeontology to archaeological studies and the use of our nannofossil collection. My colleague Tom Hill has just returned from a meeting on 'Geological applications in Archaeology' so this subject is receiving a lot of interest at the moment.

 

Just before Christmas I had an enquiry from the British Museum asking me to provide a high definition image of a nannofossil for their multimedia gallery guides. The image was taken by my former colleague Jeremy Young as part of research on the Folkton Drums published in the journal Antiquity in 2004 with British Museum staff Andrew Middleton and Janet Ambers.

 

The Folkton Drums

 

These carved stone cylinders known as the Folkton Drums were found associated with a child's burial site at Folkton near Filey northeast Yorkshire. The diameter of the largest is 146mm and they are made of incised stone with a grooved ware pottery design indicating a probable Later Neolithic age of about 2,500-2,000 BC.

 

Folkton_Drums_AN00155870_001_blog.jpgThe Folkton Drums. Image copyright: The Trustees of the British Museum, ref AN155870001, registration number 1893,1228.15.

 

Nannofossils and the museum collection

 

Jeremy Young was asked to analyse a very small amount of material removed from a blemish on the bottom of the smallest item. At the time it was not known if the stone was chalk or magnesian limestone. Chalk contains the remains of tiny calcareous coccolith plates formed by a unicellular plant called a coccolithophore. These are present in the oceans of today and are widely used for studies on recent changes to our oceans and environment.

 

The Museum houses a large collection of fossil and recent coccolith preparations, and images made by Jeremy Young. Because most coccoliths are less than a thousandth of a millimetre in size, it is very difficult to isolate them as individual specimens or to find the same specimen again even using a scanning electron microscope. As a result, images are just as important as the preparations from which the images were made and species are often defined by images alone. We have a collection of tens of thousands of such images.

 

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A  false coloured scanning electron microscope image of the fragment of Folkton Drum analysed by Jeremy Young.
The scale bar is 10 microns which is 0.01 mm.

 

What the nannofossils told us?

 

The fragment contained a typical late Cretaceous coccolith assemblage dominated by Watznaueria barnesae, Biscutum constans and Prediscosphaera cretacea. The species Micula staurophora suggests a Coniacean-Masstrichtian age of the Cretaceous (c. 65-85 Mya). The coccolith evidence suggests that the drums were made from deposits of the Upper Chalk rather than Magnesian Limestone.

 

Chalk is available locally and Magnesian Limestone from deposits about 45kms away. However, the results cannot show for certain that the chalk used was derived locally as the outcrop of the Upper Chalk Formation covers a large area of England. A non-destructive method called Raman Spectroscopy used by Janet Ambers at the British Museum also confirmed a chalk rather than Magnesian Limestone composition.

 

Where to see them?

 

The Folkton Drums can been seen in Gallery 51 at the British Museum. The nannofossil image is shown as part of the British Museum multimedia guide available in 11 different languages on request. If you are interested in the subject of 'Geological applications in Archaeology' then further details can be found via the University of Leicester web site.

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Some of the Museum's most important ostracod specimens were re-examined recently using synchrotron technology. The results published in the journal Science showed that these very delicate but exquisitely preserved fossils gave evidence for reproduction using giant sperm back in the Cretaceous period about 100 million years ago.

 

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A scanning electron microscope of an exceptionally preserved ostracod from Brazil showing details of unusually preserved soft body parts.

 

From images obtained by scanning electron microscope we have known since the 1970s that the Cretaceous ostracod Harbinia micropapillosa was almost identical in body form to modern day examples. Usually ostracods, microscopic crustaceans that inhabit aquatic environments, leave only their calcareous shells in the fossil record. However, these exceptional fossils from Brazil include details of their organic soft body parts not normally fossilised.

 

These specimens were first found by legendary evolutionary biologist Dr Colin Patterson while he was studying the fossil fish from the same rock formation. He passed them to Dr Ray Bate who published them under the name Pattersoncypris. However, some ostracod workers now believe that they should be classified under the name Harbinia which was first described by a Chinese worker in 1959 and therefore takes naming priority.

 

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The European Synchrotron Research Facility (ESRF) at Grenoble in France.

 

In 2007 we had a request by Dr Renate Matzke-Karasz (University of Munich) and a group of co-workers to take our specimens to Grenoble in France to have them analysed in the synchrotron beam ID19. A synchrotron is a giant ring where electrons are accelerated to great speeds and then bent into a circular path by magnets. Strong magents are used which cause the electron beam to deviate and at this point a very bright, intense synchrotron x-ray is emitted. Sometimes synchrotrons are referred to as diamond light sources as a result. These very intense synchrotron x-rays are then focussed into a beam which can be used for analysis at a sub micrometer scale ideal for our microfossils.

 

Some types of modern day ostracods are well known for their use of giant sperm in reproduction. Dr Matzke-Karasz and her co-workers were interested to see if our fossil specimens (Robin Smith thesis collection) contained any evidence for giant sperm or the organs responsible for its production and storage. As the curator of the specimens it was my job to transport them safely to Grenoble and to handle them while they were being analysed. I also took part in the analysis which went on all day and all night for two days. Fortunately we did get some sleep as there were four of us. We took it in turns with two of us analysing the fossils and two analysing the comparative modern specimens in 6 hour shifts.

 

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Positioning the specimen so that it is aligned with the beam. (Don't worry about the scary red lines. The beam was only switched on when we were all safely out of the room!).

 

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Dr Radka Symonova (then at Charles University, Czech Republic), Renate, Dr Paul Tafforeau (ESRF) and Dr Robin Smith (Lake Biwa Museum, Japan) examining some early scans in our experimental cabin home for the two days.

 

The specimens were placed in the beam and then rotated 180 degrees while 1500 x-ray cross sections were taken at regular intervals. These x-ray images were then combined together using specially designed software to produce 3-dimensional images (Holotomographic reconstructions). Although we could immediately see evidence for important internal structures while we were analysing the specimens, a lot of work was still required to produce the final results. The slices that make these 3-dimensional images were analysed for internal structures by Renate and her team back in Germany. Artificial colours were painstakingly added to each slice by hand to show these structures more clearly.

 

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One of the x-ray cross sections of a fossil specimen before it was combined into a 3-dimensional image.

 

The results clearly showed differences between males and females. The males had distinctive tubes in the position where modern day ostracods have  a sperm pump called a Zenker's Organ. The females had inflated sacks in the position where modern day ostracods have sperm receptacles. These are only inflated once they have been impregnated with giant sperm. Our results had shown that this reproductive strategy had been in place more than 100 million years ago.

 

 

Video of a female specimen of Harbinia micropapillosa. The orange sacks are the sperm receptacles.

 

So why is this important? As I showed in the dinosaur exhibition blog item, it is vital to know how organisms reproduce so that you can correctly interpret their fossil record and distribution in modern day environments. Ostracods are often restricted to particular environments and can be useful indicators of changes in climate. This particular ostracod species is common in Cretaceous non-marine sediments offshore Brazil and is therefore of interest to oil exploration companies as a marker for key rock formations.

 

Reproduction with giant sperm is not just restricted to the ostracods as other organisms including fruit flies and some types of frog also use this strategy. The evolutionary significance and history of this type of reproductive strategy is still unclear. What is certain is that specimens in the Museum collections show that this was also happening over 100 million years ago!

 

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Some acrylic palm of the hand sized scale models produced from the 3-D synchrotron scans and used at the "Science Uncovered" event.

 

 

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I have lost track of the number of times I have explained to people what I do and they have replied that they had no idea that this type of work was going on behind the scenes at the Natural History Museum. On Friday 23rd September it was our chance to take centre stage in the galleries in Science Uncovered, the largest 'show and tell' the Museum has ever put on.

 

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Using a large plasma screen to bring tiny fossils to life (Photo by Kevin Webb and copyright Natural History Museum)

 

Explaining about microfossils can be a difficult task considering their size and relative unpopularity compared to the dinosaurs and early human fossils that were being displayed on the tables less than 10 metres away. I have previously taken part in science communication events like these and found that microscopes have been a big draw to get the crowds in. This time at Science Uncovered, I found that a large plasma screen showing some eye catching videos and images were more a effective communication tool than ever before. Members of the public were drawn towards the screen to see what I had to say about my subject.

 

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Showing a video of a living ostracod on the giant plasma screen (Photo by Kevin Webb and copyright Natural History Museum)

 

I won't say too much at the moment about what I was talking about other than I was introducing some recent studies on some of our most important ostracod collections. I intend to make that research project the subject of a future blog entitled 'What microfossils tell us about sex in the Cretaceous'.

 

The important theme to this evening was to show the relevance of our collections and research to every day life and showcase to members of the public our science. The ostracods I showed are vital to exploration offshore Brazil and West Africa in areas where oil is being found. Knowledge of the reproductive strategies of ostracods is also vital to interpreting, not just the modern day distribution of ostracods but also the fossil record. Ostracods can give detailed information about past environments (see the Ockley dinosaur blog) and are increasingly being used to interpret past climates.

 

 

A video of the living ostracod Eucypris virens. This is related to the fossil examples that I was showing. (Video courtesy of Dave Horne, Queen Mary College, University of London)

 

It is quite tiring speaking about your subject non-stop for any period of time and my voice was quite dry after an hour. I remember taking part in a similar public event entitled the 'Fossil Road Show' back in the late 1990s and losing my voice completely by the end of the day. Fortunately this time we were using a rota system that changed the staff and specimens on the Palaeontology Station every hour. After my hour was finished I was quite disappointed to be stopping and wished that I could have carried on for longer.

 

Another minor disappointment was that I did not see other aspects of the event and get the chance to fully see what my colleagues from around the museum had to say.

 

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Some scale models of the Cretaceous ostracod Harbinia micropapillosa and my badge.

 

I do have one momento from the event; a badge with 'I'm a scientist.... talk to me'. Guardian journalist Camila Rus joked that some Museum staff had intended to wear their badges on their commute to and from work. I'm not sure this would work considering the almost complete lack of action of fellow passengers when my Natasha wore her 'Please give up your seat, I'm pregnant' badge. What I do know is that large plasma screen was an enormous help to me at 'Science Uncovered' and made my job of explaining my science much easier.

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The permanent Dinosaur gallery at the Museum is open every day of the year (except 24 to 26 December) but the recent temporary exhibition 'Age of the Dinosaur' closed last week and now sets off on its travels to another temporary location. Keen eyed visitors to Age of the Dinosaur may have seen some microfossil pictures lurking at the back of the exhibit. Microfossils and dinosaurs are at different ends of the size scale so how can work on microfossils be related to dinosaur research?

 

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The display in the 'Age of the Dinosaur' exhibit including the microfossil images

 

A neat piece of work published in 2008 by several former colleagues in the Journal Cretaceous Research described some ostracods, spores and pollen from a dinosaur excavation site at Ockley in Surrey. These microfossils show that an Iguanodon died and was buried in a temporary freshwater pond, while the spores and pollen indicate that the Iguanodon lived in a world dominated by certain types of ferns and conifers. The microfossil assemblage tells us that the Iguanodon died in the early part of the Barremian, a stage of the Cretaceous 121-127 million years ago.

 

Dinosaur officionados will correct me and say that Iguanodon is now called Mantellisaurus. Details about dinosaurs can be found on the Museum web site if you are interested to read further.

 

In 2001 a large party from the Department of Palaeontology spent two weeks excavating a site at Ockley where the partial skeleton of an Iguanodon had been found by a members of a Geologists' Association field excursion. News of the find had spread very quickly to the popular press so we had to take it in turns to stay overnight in a tent at the site so that we could make sure that is wasn't ravaged by opportunist collectors.

 

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The parts of the Ockley Iguanodon skeleton that were recovered in the excavation.

 

I remember being asked to wield a pick axe and shovel so that we could clear the overlying rock from the rock bed that the fossil bones had been found in. Meanwhile my vertebrate colleagues were on their hands and knees preparing away the bones that had become exposed on the surface. These were then taken back to the museum still encased in the rock so that they could be further prepared by David Gray in the Palaeontology Conservation Unit.

 

My former colleague Susanne Feist-Burhardt collected samples for microfossil study from the dinosaur bed and the beds above and below. These were studied for palynology by MSc student Elly Nye and by David Horne and John Whittaker for ostracod microfossils.

 

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Examples of some of the spores and pollen obtained from the dinosaur site. The palynological record suggests that the dinosaur came to rest on a warm subtropical flood plain surrounded by ferns and conifers.

 

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The freshwater green algae Scenedesmus novilunaris found in the dinosaur bed suggests that its final resting place was a freshwater pond.

 

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The ostracod Cypridea clavata along with other evidence suggests that the pond dried out periodically.

 

Samples close to the dinosaur bed produced the first recognisable ostracods from the Ockley site allowing a firm date of the age of the sediments to be established. The single species of the genus Cypridea found suggests that the pond dried out on a regular basis. The eggs that this group of ostracods produces are resistant to dry periods. As a result, their relatives are often found in modern day temporary ponds. More common Cretaceous ostracods that require permanent water bodies are absent from the Ockley assemblage giving further evidence for the temporary nature of the pond where the Iguanodon came to rest.

 

This was a very interesting project to play a small part in and shows the power of tackling projects as a group. It also shows some excellent potential applications of micropalaeontology so I was very glad that it became part of the 'Age of the Dinosaur' exhibit.

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Two upcoming events will enable you to see the original specimens and the scale models of the ostracod that showed evidence of sexual reproduction through the use of giant sperm 140 million years ago.

 

At Science Uncovered on 23 September (see flyer below for details), I'll be on the Palaeontology table from 16.00-17.00. And, a few days before, at 14.30 on 19 September I'll also be taking part in the 'Microscopic sex' talk for Nature Live in the Attenborough Studio in the Darwin Centre.

 

I hope to see you at one or the other (or both!).

 

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Giles Miller

Giles Miller

Member since: Apr 21, 2010

This is Giles Miller's Curator of Micropalaeontology blog. I make the Museum micropalaeontology collections available to visitors from all over the world, publish articles on the collections, give public talks and occasionally make collections myself.

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