Author: More than a Dodo

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Death, decay and fossilization

By Duncan Murdock, Research Fellow

Our oceans, rivers and lakes teem with life of all shapes and sizes, and have done so for hundreds of millions of years. We can get a glimpse of the wonderful diversity of life deep in the Earth’s past from fossils that can be found in the rocks beneath our feet. But the fossil record is as much a history of death as it is of life.

All animals die, in huge numbers every day, but the sea beds and forest floors of the Earth are not filling up with their remains. Decay is as inevitable as death. This is good news for those left behind, but bad news for fossil hunters.

Being preserved as a fossil is very much the exception, not the rule, and the chances of anything surviving the various processes by which the component parts of an animal are lost forever are vanishingly small, even for hard parts like shells, teeth and bones. For the ‘soft’ parts of animals, such as the muscles, eyes, guts and nerves, it is nearly impossible.

But ‘nearly impossible’ is good enough when you can consider every animal that ever lived, or more importantly, died. In exceptional circumstances ‘soft’ tissues do become fossils, and when they do they invariably give an unrivalled view of an otherwise completely lost world.

Although exceptionally well preserved, this fossil of a jawless fish is not entirely complete. Some features have been preserved, like the prominent dark eye spot and gill supports just beneath, but others, such as the guts and fins, have rotted away before they could be preserved. Image: Mark Purnell, Sarah Gabbott, Robert Sansom (University of Leicester)

We know from these exceptional fossils that the path from death to fossil is not random. Yes, you have to be lucky, but the odds are very much stacked towards certain combinations of who, what, where and when.

Furthermore, decay is not the whole story. Not only does anatomical information have to survive decay, it has to undergo parallel (but distinct) processes of preservation – conversion into materials that are stable over millions of years as part of a rock. It is the balance between the loss and retention of information that seals the fate of an organism’s remains.

Three hundred million years ago, a small worm gulped its last breath and died. Its body began to rot and, were it not for the peculiar conditions of the sediments it was laid to rest in, would have been lost forever. Fortunately for us, what remained was preserved in rock – a rotten fossil. But how much rotted away before it was fossilized? By decaying modern relatives in the lab we can model this missing history, and build better-informed reconstructions of extinct animals. Image: Duncan Murdock

Left with only the lucky few, the parts of animals where retention exceeded loss, the fossil record is profoundly biased. One way to unravel this lost history of loss is it to conduct experiments, replicating decay and preservation. However, trying to make fossils in the lab, by contriving one particular set of conditions, is fiendishly complex – there are simply too many variables to set.

I have been working with researchers from the Universities of Leicester, Bristol, Manchester and University College Cork, and together we have described an alternative approach to unpack the ‘black box’ of fossilization and take each variable in turn, individually examining the different processes that result in retaining information as potential ‘fossils’ and, crucially, those that result in loss.

This cartoon illustrates the difference between experiments that attempt to replicate fossilization, treating the process as a black box, and the approach we are taking. The black box approach reveals little about the processes of information loss and information retention, the cumulative effects and interactions which ultimately results in a fossil (or, more often, not). Image: Purnell et al. 2018.

Ultimately this approach will allow more and more complex experiments to be designed, to unpick the interactions between the who, what, where and when in the lost history of death.

The techniques described here are published in Palaeontology today as ‘Experimental Analysis of Soft-Tissue Fossilization: Opening the Black Box‘, Purnell et al. 2018.

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Spiders’ eyes cast in Diamond Light

by Imran Rahman, Deputy Head of Research

There are plenty of reasons to visit Didcot. The railway station is an important junction between Oxford and the west of England, the Didcot Railway Centre houses a great collection of trains, if you like that sort of thing, and Didcot Town Football Club are currently a respectable fourth* in Division One West of the Southern League…

But if that’s not enough to tempt you, Didcot is also home to the UK’s only synchrotron – a multi-million pound facility that goes by the name of Diamond Light Source. In February, six members of the Museum’s research team visited Diamond to carry out some important experiments on spiders.

But before we get to that, what exactly is a synchrotron light source? Well, it is a type of particle accelerator which uses huge magnets to speed up tiny particles, usually electrons, until they are moving almost as quickly as the speed of light. The particles are sent flying around a ring-shaped machine hundreds of metres across – the ‘doughnut’ structure in the photo.

The Diamond Light Source synchrotron in Didcot, Oxfordshire. Particles are accelerated to close to the speed of light around the ‘doughnut’ structure. Image: Courtesy of Diamond Light Source

This beam of high-energy particles gives off large amounts of ‘light’, or electromagnetic radiation, when its direction is changed. This radiation, usually in the form of X-rays, can be funnelled down to experimental stations, known as beamlines, and used for lots of different measurements and experiments. As the UK’s national synchrotron light source, Diamond is visited by scientists from all over the world every year.

So what does a museum want with a powerful X-ray beam? One of our research fellows, Lauren Sumner-Rooney, is particularly interested in studying the eyes and brains of spiders. So the team, led by Lauren, went to Didcot to create some X-ray images of spiders from the Museum’s collections.

Ready for your X-ray close -up? A spider specimen is mounted in the I13-2 beamline at Diamond Light Source. Image: Lauren Sumner-Rooney

You may not have looked too closely at a spider’s head before, but they usually have eight eyes as well as eight legs. That said, there is actually quite a lot of variation in the number and structure of eyes between different species, and Lauren is interested in documenting this variation across selected spider families to investigate how it affects spiders’ brain structures.

Using the I13-2 beamline at Diamond, and fighting severe sleep deprivation with the aid of strategically-selected songs and snacks, the team was able to visualize details measuring less than one thousandth of a millimetre without damaging the precious specimens. They were assisted by Andrew Bodey, a senior support scientist at Diamond, and Emelie Brodrick, a PhD student at the University of Bristol.

The research team following 72 hours of very little sleep! From left to right: Ricardo Pérez-de la Fuente, Lauren Sumner-Rooney, Imran Rahman, Jack Matthews and Emelie Brodrick. Image: Emelie Brodrick

Over the course of 72 straight hours, the team scanned 116 spiders, creating about 14 terabytes of data. This will form the basis of a variety of exciting scientific research projects at the Museum over the coming years. Watch this space for the results!

*Didcot Town were fourth in the Southern League Division One West table on 8th March. The Museum accepts no responsibility for any change in their position after this date.

Top image of Pholcus moca courtesy of Smithsonian Institution.

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Carnivore conservation

A new choose-your-own-adventure board game created by researchers from the University of Oxford’s Department of Zoology puts players centre-stage in a global carnivore conservation challenge. The educational game is launching a Kickstarter fundraising campaign today and here co-designer Dr Cedric Tan tells us all about it…

Have you ever wondered what it’s like being a conservation biologist? We have spent the past year creating and testing a brand new board game – The WildCRU Game: Global Carnivore Conservation – that reveals some of the challenges faced by conservationists, the animals themselves, and the indigenous people who live with them. We’re now looking to get the game out to schools and communities all across the world with a £40,000 Kickstarter funding campaign featuring lots of rewards and discounts for our backers.

The game has been co-designed by Jennifer Spencer and myself to appeal to non-scientists and people of different ages. Players work together cooperatively as WildCRU researchers to gather the resources to complete carnivore conservation projects across the globe.

Stories in the game are taken directly from the real experiences of the WildCRU team. Players must decide what to do in choose-your-own-adventure-style encounters to gather the equipment, personnel, and transport resources they need for their projects.

In developing this game, we chose six varied WildCRU projects including the Hwange Lion Research project, based in Zimbabwe, and the famous water vole study in the UK, to show players the breadth of WildCRU’s research.
– Co-designer Jennifer Spencer, WildCRU

Multiple choice research questions are also based on real WildCRU research; they reveal more about the environment of each project – the flora, herbivores, competitor carnivores, and study species of the study sites. With the additional pressure of Global Events, players will learn about how difficult wildlife conservation projects can be.

It has been great to see that the game appeals to both kids and adults. People have found it to be an immersive experience in which players experience the challenges of real people, real situations and real research. We also hope that the game will provide local families with the opportunity to learn about the wildlife around them, and how to live in harmony alongside it.

Through the game and our other education efforts we’re hoping to increase environmental awareness and to introduce a wide variety of people to the science and processes behind real-world conservation.

Images and video: Laurie Hedges (lauriehedges.com)

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Movers and settlers

Our new exhibition Settlers, which opens today, shows that the history of the people of Britain is one of movement, migration and settlement. Here, exhibition writer Georgina Ferry finds that Britain has been receiving new arrivals since the last Ice Age.  

In Britain following the Brexit vote, the word ‘migration’ has taken on an emotional and political charge. A new exhibition opening today takes a long-view of the movement of people, looking in particular at how migration has formed the British population.

Settlers: genetics, geography and the peopling of Britain tells the story of the occupation of Britain since the end of the last Ice Age, about 11,600 years ago. From this perspective, today’s pattern of movement into and out of the country is only the latest in a long history of alternating change and stability that has made the people of Britain who they are today.

Hand axes from Wolvercote, Oxford
About 340,000 – 300,000 years ago, when conditions were slightly warmer than at present, Neanderthal hunters lived alongside a channel of the Thames near Oxford where the village of Wolvercote now stands. They made flint hand axes – all-purpose butchering, digging and chopping tools. They hunted animals now extinct in Britain.

Tracing these movements has been a fascinating detective story, with clues coming from many different types of evidence. The starting point for Settlers is a remarkable study carried out by Oxford scientists, who used DNA samples from contemporary British volunteers to trace the origins of the people who settled Britain between the end of the Ice Age and the Norman Conquest of 1066. One striking finding is that the bonds that unite Celtic communities in Cornwall, Wales and Scotland are largely cultural – genetically these groups are quite distinct.

Drinking horn finial of copper alloy and glass, 9th century – Northern Ireland. The Ashmolean Museum, University of Oxford

The genetic evidence adds a new dimension to the archaeological story, based on artefacts left behind by our ancestors, or other historical signposts such as place names. For example, although occupying Roman armies left us the names of their forts and cities, they don’t seem to have left much of their DNA. They came, saw and conquered, but didn’t stay in large enough numbers to make a genetic impact on the native British population. In contrast the Anglo-Saxons, who arrived after the Romans withdrew, left a strong genetic signature everywhere except Wales and the Scottish Highlands.

It took 2,000 volunteers and software that can distinguish tiny differences to arrive at the various regional clusters that came out of the study. When you visit the exhibition, you can play a fascinating interactive lottery game to see just how unlikely it is that genes from any specific ancestor of more than a few generations will still be in your DNA.

This map, created by the People of the British Isles study, is the result of comparing patterns in the DNA of a carefully selected sample of around 2,000 modern British people. It provides new evidence about links between genetic ancestry and geographical origins.

The story of movement and settlement doesn’t stop in 1066. Researchers in Oxford’s School of Geography have plotted census data since 1841 against global events, from the persecution of Russian Jews to the enlargement of the European Union, to illustrate the ebb and flow of people from and to Britain that has produced the current population mix. Another interactive lets you compare your own family’s journey with those of all the other visitors.

We will have to wait until the census of 2021 to know what a difference Brexit will make, but we can be sure that people will be arriving and leaving for a lot longer than that.

www.oum.ox.ac.uk/settlers

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Bound by blood

It may sound like we’ve stumbled into a script-writing session for Jurassic Park, but one of our research fellows, Dr Ricardo Pérez-de la Fuente, along with an international team, has discovered a parasite trapped in amber, clutching the feather of a dinosaur. This small fossilised tick, along with a few other specimens, is the first direct evidence that ticks sucked the blood of feathered dinosaurs 100 million years ago. Ricardo tells us all about it…

The paper that my colleagues and I have just published provides evidence that ticks fed from feathered dinosaurs about 100 million years ago, during the mid-Cretaceous period. It is based on evidence from amber fossils, including that of a hard tick grasping a dinosaur feather preserved in 99 million-year-old Burmese amber.

Fluorescence detail of the studied hard tick grasping a dinosaur feather. Extracted from the publication.

The probability of the tick and feather becoming so tightly associated and co-preserved in resin by chance is virtually zero, which means the discovery is the first direct evidence of a parasite-host relationship between ticks and feathered dinosaurs.

Fossils of parasitic, blood-feeding creatures directly associated with remains of their host are exceedingly scarce, and this new specimen is the oldest known to date. The tick is an immature specimen of Cornupalpatum burmanicum; look closely under the microscope and you can see tiny teeth in the mouthparts that are used to create a hole and fix to the host’s skin to suck its blood.

The structure of the feather inside the amber is similar to modern-day bird feathers, but it could not belong to a modern bird because, according to current evidence at least, they did not appear until 26 million years later than the age of the amber.

Feathers with the same characteristics were already present in multiple forms of theropod dinosaurs –  the lineage of dinosaurs leading to modern birds – from ground-runners without flying ability, to bird-like forms capable of powered flight. Unfortunately, this means it is not possible to determine exactly which kind of feathered dinosaur the amber feather belonged to.

But there is more evidence of the dinosaur-tick relationship in the scientific paper. We also describe a new group of extinct ticks, created from a species we have named Deinocroton draculi, or “Dracula’s terrible tick”. These novel ticks, in the family Deinocrotonidae, are distinguished from other ticks by the structure of their body surface, palps and legs, and the position of their head, among other characteristics.

Blood-engorged Deinocroton draculi tick (female). Extracted from the publication.

This new species was also found sealed inside Burmese amber, with one specimen remarkably engorged with blood, increasing its volume approximately eight times over non-engorged forms. Despite this, it has not been possible to directly determine its host animal:

Assessing the composition of the blood meal inside the bloated tick is not feasible because, unfortunately, the tick did not become fully immersed in resin and so its contents were altered by mineral deposition.
Dr Xavier Delclòs, an author of the study from the University of Barcelona and IRBio.

But there was indirect evidence of the likely host for these novel ticks in the form of hair-like structures called setae from the larvae of skin beetles, or dermestids, found attached to two Deinocroton ticks preserved together. Today, skin beetles feed in nests, consuming feathers, skin and hair from the nest’s occupants. But as no mammal hairs have yet been found in Cretaceous amber, the presence of skin beetle setae on the two Deinocroton draculi ticks suggests that their host was in fact a feathered dinosaur.

The hair-like structures, or setae, from skin beetles (dermestids) found attached to two Deinocroton ticks fossilised inside amber, in comparison with extant ones. Modified from the publication.

Together, these findings tell us a fascinating story about ancient tick behaviour. They reveal some of the ecological interactions taking place among early ticks and birds, showing that their parasite-host relationship has lasted for at least 99 million years: an enduring connection, bound by blood.

The paper “Ticks parasitised feathered dinosaurs as revealed by Cretaceous amber assemblages” is published as open access in Nature Communications. Direct link: http://dx.doi.org/10.1038/s41467-017-01550-z

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Clean as a new pin

The spiky customer above has enjoyed a serious spruce-up from Stefani Cavazos, our current intern from UCL’s MSc in Conservation for Archaeology and Museums. Stefani tells us how she got this Spot-fin Porcupinefish looking shipshape, without receiving any serious injuries.

So far at the Museum I have been working on a range of specimens, from taxidermy and wet specimens to cleaning the whales, but my favourite project so far has been the conservation of this Spot-fin Porcupinefish from the displays. It is part of what is known as the Christ Church Collection, which came to the Museum in 1860. This makes the Porcupinefish at least 150 years old.

The specimen itself was covered in dust and all five of its fins were backed with deteriorating cardboard pieces. These were most likely attached to give some support during a previous restoration attempt. Unfortunately, cardboard is not a conservation grade material because over time it becomes acidic. Temperature and humidity changes in the Museum have caused it to bend forward, pulling the fins out of shape, so we felt it should be removed to prevent further damage.

The Spot-fin Porcupinefish (Diodon hystrix) before conservation treatment (left images), and close ups of the cardboard backings on the left pectoral fin (right images), where staining and bending are visible. The red arrow indicates where the paper has separated from the fin, and how thin the fins are.

The first step in the treatment was to clean the surface of the Porcupinefish using warm water and a cotton swab. This allowed me to get into the nooks and crannies of the body whilst (mostly) avoiding being poked by its spines. Next, the cardboard backings were softened with water vapor, causing them to break apart so they could be removed easily using tweezers and a scalpel blade.

Conservation can feel like detective work since we often uncover interesting information about specimens as we work on them. In this case, as we removed the cardboard pieces, we found writing on the underside. It appears to be from a shoe box! Though unexpected, it wasn’t entirely surprising. Preparators in the past used whatever materials were available to them at the time.

(Left) The cardboard was carefully removed from the caudal (tail) fin. (Right) The cardboard once removed from the fin, it appears to be from a shoe label.

After detaching the cardboard from all the fins, the remaining ink and adhesive residues were removed using a 50/50 alcohol and water mixture applied with a cotton swab. The edges of the fins were then coated with two thin layers of an acrylic adhesive to prevent any further breakage and to offer some support to the weakest areas. Cleaned, and free of damaging materials, this Porcupinefish is now ready to go back on display!

Photos of the Spot-fin Porcupinefish after treatment was completed. Without the cardboard backings, the fins are somewhat translucent.
Stefani takes her finished work out to one of our regular Spotlight Specimen sessions, giving visitors the chance to get a closer look and ask questions.