Reconstructing the cretaceous with bones and amber

A double window into the past

Post by Dr Ricardo Pérez-de la Fuente, Deputy Head of Research

Nature is wonderfully imperfect, and the data that we can gather from it is even further from perfection. Fossil localities, even those providing exceptionally well-preserved fossils, are inaccurate records of the past. Fossils can form from a variety of matter including organisms, their remains, or even traces of their activity. Yet not all of the material that can get fossilised at a particular site actually will. Among other factors, biases in the fossil record result from the nature of the materials responsible for fossilisation – usually sediments which are in the process of turning into rocks. In most cases, fossil localities offer us only a single ‘window of preservation’ – a skewed geological record of the ancient ecosystem that once existed there.


In 2012, a rich vertebrate bone bed was documented at the Ariño site in Teruel, Spain. Since then, researchers have unearthed more than 10,000 individual fossil bones, from which they have discovered new species of dinosaurs, crocodiles, and turtles. Plant fossils were also found, including pollen grains and amber, which is fossilised resin. Although amber was known to occur in this locality, this sort of material had remained unstudied… until recently.

Over the summer of 2019, I joined my colleagues to carry out amber excavations in the Ariño site – an open-pit coal mine that has an almost lunar appearance due to the dark carbonate-rich mudstone rocks and the total lack of vegetation. The scorching heat during a very hot summer was a bit maddening, but I did try to enjoy my yearly dose of sun before returning to the UK!


Resin pieces can be transported significant distances by runoff water before depositing on their final burial location, where they slowly transform into amber. However, we found amber pieces that had not moved from their original place of production. These large, round-shaped pieces preserved delicate surface patterns that would have been polished away even by the slightest transport. The resin that produced these amber pieces was formed by the roots of the resin-producing trees, and resembles sub-fossil resin my colleagues found in modern forests from New Zealand.

Large amber piece produced by roots (left) and assemblage of smaller amber pieces (right) from Ariño (Teurel, Spain).
Large amber piece produced by roots (left) and assemblage of smaller amber pieces (right) from Ariño (Teurel, Spain).

The small amber pieces from Ariño contain an unusual abundance of fossils. These pieces come from resin produced by the branches and trunk of the resin-producing trees. From the almost one kilogram of amber we excavated, we identified a total of 166 fossils. These include diverse insects such as lacewings, beetles, or wasps, and arachnids such as spiders and mites. Even a mammal hair strand was found!1


We now know that the Ariño site provides two complementary windows of preservation — a bone bed preserving a rich variety of vertebrate animals, and amber with abundant inclusions. Aside from Ariño, only three localities that preserve both dinosaur bone beds and fossiliferous amber have been reported in Western France, Western Canada, and North Central United States. However, in these cases, either the bone bed or the amber have offered a much more modest abundance and diversity of fossils. Some of the fossils from these localities also show signs of significant transport, which means that the organisms could have inhabited different, distant areas even though they fossilised together. This makes Ariño unique because it offers two valuable ‘windows of preservation’ from the same ecosystem.

Thanks to all this evidence and other data, we have been able to reconstruct an ancient terrestrial ecosystem – a 110-million-year-old coastal swamp – with unprecedented detail and accuracy.2 The inherent incompleteness of the fossil record will always remain a headache for palaeontologists… but localities like Ariño make the data that we can recover from the past a bit more complete.

Reconstruction of the coastal swamp forest of Ariño, in the Iberian Peninsula, from 110 million years ago. Author: José Antonio Peñas. Source: Álvarez-Parra et al. 2021.
Reconstruction of the coastal swamp forest of Ariño, in the Iberian Peninsula, from 110 million years ago. Author: José Antonio Peñas. Source: Álvarez-Parra et al. 2021.

If you want to learn more about amber excavations, check out this post on Excavating Amber.


1Álvarez-Parra, Sergio, Ricardo Pérez-de la Fuente, Enrique Peñalver, Eduardo Barrón, Luis Alcalá, Jordi Pérez-Cano, Carles Martín-Closas et al. “Dinosaur bonebed amber from an original swamp forest soil.” Elife 10 (2021): e72477.

2Álvarez-Parra, Sergio, Xavier Delclòs, Mónica M. Solórzano-Kraemer, Luis Alcalá, and Enrique Peñalver. “Cretaceous amniote integuments recorded through a taphonomic process unique to resins.” Scientific reports 10, no. 1 (2020): 1-12.

Crunchy on the outside

By Susie Glover, HOPE Learning Officer

We have an ambitious project underway at the Museum, to preserve a unique and scientifically important collection of over one million British insects. It’s called HOPE for the Future, after the Hope Entomological Collections, and we are keen to shout about how these specimens can help us understand biodiversity, habitats and ecologies.

The learning team behind the project are today launching a new blog for young people interested in entomology. Intriguingly, it’s called Crunchy on the Outside, but please don’t confuse this with the similar, but fundamentally different, mid-’90s advertising campaign for the Dime bar.

A high magnification image of an insect, face-on, showing large proboscis and brown body.
One of many weird and wonderful specimens from our collection, the Acorn Weevil (Curculio glandium).
Here is a peek at some of the tools of the trade, used to move and mend specimens like this moth.

Crunchy will be crammed full of interesting insect info, fun things to make and do, a peek behind the scenes at the Museum, and news from people, past and present, who work in the field of entomology. The odd bad joke may also worm its way in (What do butterflies sleep on? Cater-pillows).

The blog will also be a platform for young people to have their say, about the topics covered on Crunchy itself, as well as on the activity of the Museum. It will give them first dibs on access to related events too. You can check it out, follow, and share at crunchyontheoutside.com.

HOPE for the Future is funded by the National Lottery Heritage Fund.

Eggs in the tower

By Chris Jarvis, Education Officer

We have our first eggs! After an earlier than usual return from the warmth of Africa, followed by a cold snap of north easterly winds, our swifts have begun to lay their first clutches of eggs in the tower.

Ten eggs were counted on 14 May, some in pairs and some lying singly on nests. Birds in other nests appear to be incubating as well, sitting in pairs and screaming out at any newcomers investigating possible nesting sites.

More swifts are arriving daily and screaming parties are urgently exploring for potential nesting locations. They buzz the tower’s nesting holes at speed and bang on the entrances with their wings like naughty teenagers playing a vociferous game of ‘knock and run’!

Typically, no bird has yet elected to nest in either of the boxes fitted with webcams. But as the weather warms and more swifts take up residence every day, we’re sure you’ll be able to follow all the drama of the Swifts in the tower very soon.

The swifts circle the Museum tower looking for suitable nesting sites

The delicate art of laying
Swifts tend to lay their eggs in the mornings, usually between 8am and 11am. The small, fragile eggs are white to reflect light, an adaptation shared by most cavity-nesting birds that makes the eggs more visible to adults in the dark of the nest.

The first eggs this year appear to be quite early in the season compared with the observations by David Lack in the 1940s and 50s. At that time, when the study of the Museum’s colony began, the first eggs were recorded on average between 17 and 22 May, but sometimes none was laid until the first week of June.

Egg production and laying in swifts are very closely tied to the weather, and production seems to be triggered by the availability of food. Swifts feed exclusively on small airborne insects, which are more abundant in the warm thermals and light winds we experience on good summer days.

It takes a swift five days to produce and then lay an egg. Five days before our first eggs were laid it was sunny and warm, just before the strong, cold north easterly winds swept down over the weekend and lowered the temperature. The warmer early start to the summer seems to have triggered this early laying; whether this is a trend that is increasing as the climate changes is something we should able to answer with long-term datasets provided by studies like this.

Dealing with the weather
Whatever climate change has in store for us it is becoming clear that we won’t experience repeated hot summers. The unpredictability of the British summer reigns supreme.

Swifts have evolved several wonderful adaptations to deal with the vagaries of our weather. Their eggs can be left without an adult to keep them warm for several days. There are records of eggs being left unattended for almost a week and still developing normally. Although adults usually take it in turns to feed and brood the eggs, sometimes during the day the eggs are left unattended by both birds which are then able to forage far afield for food.

Unlike many songbirds which produce one egg a day until their clutch is completed, swifts are able to space out their laying. In a clutch of two or three eggs, the second or third may be laid two or three days after the first, depending on weather conditions. The birds will also limit the size of clutches, with clutches of three eggs the average in warm weather and two eggs the average in cold weather. This helps the adults to supply all of their young with enough food.

Finally, swifts may also eject eggs and lay a second clutch. Some studies have linked this behaviour to cold weather but this has not always been the case at the Museum colony and is a further line of investigation in the ongoing studies of these most secretive of birds.

From laying to hatching usually takes about 19 days, depending on the weather. So we should be seeing our first chicks at the very beginning of June, hopefully streaming live on the Swiftcam

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Screaming parties prospecting for nest sites are a good way for you to see if you have nesting swifts nearby. Any records really help with our understanding of the current population in the UK. You can help conservation and recording for the Oxford Swift City project, or use the RSPB’s Swift Mapper for the rest of the UK.

Mammoth tusks and cocktail sticks

By Pete Brown, Move Project Assistant

As part of the Museum of Natural History Move Project Team I have helped move and repackage tens of thousands of specimens since 2017, removing boxes filled at any time over the last 150 years from their old storage location in a deconsecrated church building near Oxford.

At our new facility we have been documenting and repacking the contents in new, clean containers and placing them in environmentally stable, safe warehouses specially adapted for museum storage.

Some objects are trickier to store than others. Things that are long, heavy, curvy and fragile are tricky. Mammoth tusks are long, heavy, curvy, and fragile. This means:

  1. They’re not going to fit in a normal box.
  2. They’re going to be difficult to move around.
  3. That beautiful curve will mean that all the weight of the tusk may be bearing down on just two small contact points where the tusk meets the storage surface.
  4. Because those points are fragile, they’re likely to get damaged.

A lot of weight can rest on small areas of the tusk, putting strain on the specimen and potentially causing damage

The tusk in this article is a prime example. The area nearest the camera in the photo above provided just a tiny point of contact with the floor and was very loose, almost to the point of detaching. It needed to be repaired, and stored in such a way that it wouldn’t get damaged again.

Pete Brown carries out delicate conservation work on the mammoth tusk

I filled some of the missing areas around the fragile area with an easily removable fine acrylic putty to prevent further movement and loss of the original material. A cotton tape sling helped to suspend the fragment in place during the work.

Thick plastazote provided a sturdy, slightly yielding bed for the tusk to lie on in storage, but to prevent the tusk from getting damaged again more needed be done to reduce the pressure on the points of contact.

The dark grey foam material, plastazote, is often used as a cushioned support for museum objects

I cut depressions into the plastazote where the tusk naturally lay to increase the total surface area supporting the weight of the tusk, and fixed plastazote wedges and supports in place with cocktail sticks to again increase the contact area and prevent movement. Cotton fabric ties, fed through slits in the plastazote, also helped to guard against unwanted movement.

Cocktail sticks: not just for cheese and pineapple

The repaired end of the tusk is now only supporting a fraction of the weight it used to, and once the tusk and the plastazote bed are placed into their new custom-made crate it will be ready for long-term, safe, damage-free storage!

The end of the tusk after treatment

To keep up with all the move project action, follow the museum hashtag #storiesfromthestore on Twitter @morethanadodo.

 

Bee beautiful

Our conservator Bethany Palumbo tells us how she restored a beautiful 19th-century papier-mâché model of a honeybee hive, created by master model-maker and anatomist Louis Thomas Jérôme Auzoux

Louis Thomas Jérôme Auzoux

Although the Museum’s collections are mostly of organic specimens, we also hold a fascinating collection of scientific models made to represent the natural world, made from all types of materials, from wax and cardboard to plaster and paint.

We are lucky enough to own a model made by esteemed French anatomist Louis Auzoux (1797-1880), who in the late 19th century developed a method of building strong yet light papier-mâché models that could be taken apart and rebuilt, allowing internal elements such as tissues and organs to be studied in detail.

Model of a honeybee hive in box with six bees, by Louis Auzoux

While Auzoux made many models demonstrating human anatomy, he later expanded his business to include magnified models of plants and insects. The model we have is of a honeybee hive, containing six beautiful bees.

The hive, painted with a protein-based paint and varnished with gelatine, is large enough to allow the viewer to see the fine details of the hive, including individual chambers containing tiny larvae.

As you can see in the image at the top of the article, the bees themselves are also intricately painted, with rabbit hair used to simulate their natural fuzz, and delicate wings constructed from metal wire.

While there was much to admire about this model, it was in received in poor condition. Previous restoration attempts had introduced many materials that were now failing. There were fills, constructed of paper, applied to areas in an attempt to hide cracks in the original model. These were covered in oil paint, which was dripping over the original paintwork and had become brittle and discoloured.

Oil paint layers were peeling from the model

The whole hive was coated in a layer of cellulose nitrate film, a popular coating in the mid-20th century which was used as protection and to create a gloss finish. This coating doesn’t age well, resulting in peeling. It had also been applied to the bees themselves, clumping together the bee ‘fuzz’ and disguising the paintwork underneath.

The priority for treatment was to return the model to its original form while stabilising it for the future.

I undertook treatment in several stages over the course of six months. First, the cellulose nitrate film was removed from all areas using acetone, which could be applied with a cotton bud and fortunately didn’t affect the paint layer beneath.

Fill material used to cover previous damage had become discoloured

The next stage was to remove the discoloured oil paint from the hive. This was done manually using metal and wooden tools lubricated with white spirit, which were used to gently scrape the surface under magnification. This revealed old fills on the hive, made from a combination of plastic tape, paper and old adhesives which also needed to be removed. They were easily softened with water and gently peeled away.

Once all unstable introduced materials were removed, work began to stabilise the original model. The bees were suffering from paint cracking and peeling, as seen in the magnified photograph below.

Peeling paint at 6x magnification

We decided to consolidate this using gelatine as it would be in keeping with the original construction and could easily be reversed if necessary. Gelatine was mixed in water and warmed to make it a thin consistency, and then applied with a paintbrush. Once the paint flakes had softened they could be gently pressed down. Gelatine was also used with acid-free tissue to stabilise the cracks and areas of surface loss on the hive.

With the hive and bees now clean and stable, the quality of this piece and its incredible paintwork can really be admired. We hope to put it on display soon for all our visitors to enjoy!

Pieces of a plesiosaur

We’ve just opened a brand new, permanent display called Out of the Deep, featuring two beautifully preserved plesiosaur skeletons. Remarkably, both of these marine reptile fossils have skulls, which is more unusual than you might think. Dr Hilary Ketchum, collections manager in the Museum’s Earth Collections and curator of Out of the Deep, describes how the skull of the long-necked plesiosaur made it safely from a quarry to a museum display.

At the bottom of a clay pit in 2014, palaeontologists from the Oxford Clay Working Group discovered a 165-million-year-old fossil plesiosaur skeleton, and they knew they had found something special. Plesiosaur bones are fairly common in the quarry, but skeletons are rare. Skeletons with skulls are rarer still. Fantastically, at the end of their newly-found plesiosaur’s neck was a skull. Barely visible underneath the clay, only the tip of the snout and a few teeth were exposed.

Can you see the skull? Fossil hunting in the quarry takes time, patience and a good eye to distinguish between bones and clay. Image: Mark Wildman, Oxford Clay Working Group.

Plesiosaur skulls are usually made up of around 33 bones, not including the tiny bones from inside the eye sockets, called the sclerotic ring. The skull bones are among the smallest and most fragile in the entire skeleton. This means they are much less likely to be preserved, and less likely to be discovered, than the larger and more robust backbones and limb bones.

A plaster jacket was made around the skull while still in the quarry.
Image: Mark Wildman, Oxford Clay Working Group.

When the plesiosaur skeleton arrived in the Museum in 2015, the skull and some of the surrounding clay was encased in its protective plaster field jacket. As tempting as it was, instead of cracking open the jacket straight away, we decided on a more technological approach. Professor Roger Benson and Dr James Neenan took the specimen to the Royal Veterinary College to use their enormous CT scanner, normally used for scanning horses and other large animals, and took thousands of X-rays of the jacket. This allowed them to build up a 3D model of the fossil inside – our first tantalising glimpse of the whole skull!

The CT scan of the plaster jacket (left) revealed the location of the skull inside the jacket (middle). The jacket was then digitally removed (right) to reveal a 3D image of the skull.

Having the CT scan of the skull was like having a picture on a puzzle box
Juliet Hay, Earth Collections conservator and preparator

Although the CT scan was incredibly useful, we still had to proceed with the preparation with caution. It was possible that not all of the bones had not been detected by the scanner, especially the incredibly thin bones of the palate.

After opening the plaster jacket, Juliet began to carefully remove the clay from around the fossil bone.

Slowly and carefully, Juliet and I removed the soft clay from around the skull. The weight of clay pressing on top of the skull for millions of years had crushed it, breaking some of the bones into a lot of smaller pieces. In order to keep track of them we attached a number to each piece of bone and photographed it from several different angles before removing it from the jacket.

Each individual bone was mapped using a numbering system. The numbers were attached with the conservation adhesive Paraloid B72 in acetone, so that they could be easily removed later.

The plesiosaur’s pointed teeth being revealed.

When all the bones had finally been removed from the clay, we had over 250 pieces. Next came the challenge of the three-dimensional jigsaw!

With knowledge about plesiosaur skulls from my PhD, and some extra expert help from Roger Benson and Dr Mark Evans, Curator of Natural Science and Archaeology, New Walk Museum and Art Gallery, I was able to build up the skull, piece by piece, until it was nearly whole again.

After many months of painstaking work, the beautifully preserved skull of this long-necked plesiosaur can finally be seen in the Out of the Deep display.

Amazingly, the skull is even more complete and more beautifully preserved than we could tell from the CT scan. The sutures between the individual bones can be seen in exquisite detail, and even though I work with fossils every day, I still find it amazing that it is 165 million years old.

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With special thanks to:

Oxford Clay Working Group: Mark Wildman, Carl Harrington, Shona Tranter, Cliff Nicklin, Heather Middleton, and Mark Graham, who uncovered and excavated the long-necked plesiosaur.

Forterra, for generously donating the plesiosaur skeleton to the Museum, after it was discovered in a Forterra quarry.