Rare Jurassic mammal fossil from Scotland is new species

By Elsa Panciroli, Research Fellow

This week my colleagues and I announced the discovery of a new species of mammal from the time of dinosaurs. It is one of two rare skeletons we’re studying from the Isle of Skye in Scotland. These mouse-like animals lived in the Middle Jurassic (166 million years ago), and tell us about the evolution of mammals in the time of dinosaurs.

The two fossils belong to Borealestes serendipitous and Borealestes cuillinensis. B. serendipitous was the first Jurassic mammal ever found in Scotland, known originally from pieces of fossil jaw found on Skye in 1971. In our new paper, we describe the skull of a partial skeleton of this species, found in 1972 by the original discoverer of the site, Dr Michael Waldman and his colleague Prof Robert Savage. But this exceptional fossil lay unstudied for over 40 years. Only now is it giving up its secrets thanks to powerful synchrotron X-ray scans, which reveal the anatomy in incredible detail.

The other fossil skeleton was found in 2018 by my colleague Prof Richard Butler. After taking it back to the lab and CT-scanning it, we realised it was a new species. We named it Borealestes cuillinensis in honour of the Cuillin mountain range on Skye (Gaelic: An Cuiltheann), a stunningly jagged set of peaks that overlooks where the discovery was made.

The fossil jaw of new species, Borealestes cuillinensis, moments after its discovery. By Elsa Panciroli

Most ancient mammals are only known from a few teeth and jaws, so these skeletons are exceptionally rare. They are currently the most complete Jurassic mammals described from the UK.

The Middle Jurassic is an important time in animal evolution, because it marks an increase in the diversity of lots of different groups. Just afterwards, in the Late Jurassic, there are many new species of mammals, amphibians, small reptiles and dinosaurs, which flourish into the Cretaceous period. All of this diversity began in the Middle Jurassic, but fossils from that time are rare, making it difficult to unpick the causes of these changes. This means that any material from that time period is extremely important to our understanding of the course of evolution, and the drivers of animal diversity.

Fieldwork team on the Isle of Skye: (L to R) Roger Benson (University of Oxford), Richard Butler (University of Birmingham), Elsa Panciroli (OUMNH and National Museums Scotland), Stig Walsh (National Museums Scotland).

Our team have been carrying out fieldwork and research on Skye for the last decade. It includes researchers from National Museums Scotland and the universities of Oxford and Birmingham. We are working on many more exciting fossils from the island, so keep an eye out for the next discovery!

Read the paper ‘New species of mammaliaform and the cranium of Borealestes (Mammaliformes: Docodonta) from the Middle Jurassic of the British Isles’ published today in the Zoological Journal of the Linnean Society.

Top image: Digital reconstruction of two Jurassic mammal skulls. (c) Matt Humpage

Celebrate science in a cemetery

By Nina Morgan, Gravestone Geology

Cemeteries not only provide a peaceful place to commemorate the dead, and observe and enjoy nature; they are also wonderful repositories for the study of local history and art. But that’s not all. Cemeteries also offer an easy introduction to science that anyone can enjoy.

A visit to a cemetery presents a wonderful way to learn about geology and the other sciences, such as chemistry, physics and engineering, that underpin it. For geologists – whether amateur, student or professional – almost any urban cemetery provides a valuable opportunity to carry out scientific fieldwork at leisure, right on the doorstep, and at no cost.

Headington Municipal Cemetery, Oxford

Geology on show

Because gravestones are made from a wide variety of rock types formed in a range of geological settings, cemeteries can be geological treasure-troves. Many headstones are made of polished stone, so reveal details – such as minerals and crystal features – that are not easy to see elsewhere. Some demonstrate the textures and mineral composition of igneous rocks – rocks formed when molten magma cooled and solidified. Others are happy hunting grounds for lovers of fossils. Some gravestones reveal sedimentary structures that show how the rock was originally deposited. Others provide clues to earth movements and environments that occurred hundreds of millions of years ago.

For those interested in engineering, examination of gravestones can also provide useful information about topics ranging from weathering of stone to atmospheric chemistry, effects of pollution, stability and settling in soils and land drainage. 

St Andrews Church in Headington, Oxford

Cemeteries in Oxford include ancient churchyards, such as St Andrews Headington, as well as Victorian cemeteries like Holywell (pictured top) and St Sepulchres, and more modern burial grounds, such as Headington Municipal cemetery. Together they exhibit the main features and stone types that can be seen in cemeteries all around Britain.

St Sepulchres Cemetery, Oxford

In the short video below, filmed in the churchyard of St Mary and John in Oxford’s Cowley Road, Philip Powell and I introduce the basics and show you how to get started in exploring these geological gems. If you want to learn more, visit www.gravestonegeology.uk. But be warned – gravestone geology can be addictive. Once you’ve got your eye in, you’ll never look at cemeteries in the same way again!

All images and video by Mike Tomlinson.

When life got hard

By Dr Duncan Murdock, Research Fellow

Whether you’re a great white shark with a deadly conveyor belt of teeth, a deep sea snail with a coat of armour or a coral building the Great Barrier Reef one polyp at a time, mineralized skeletons are a crucial part of many animals’ way of life. These hard skeletons – shells, teeth, spines, plates and bones – are all around us.

The fossil record is full of the remains of the skeletons of long-extinct critters, so much so that entire layers of rocks can be composed almost completely of them. But this has not always been the case…

A piece of 425 million year old sea floor containing the skeletons of trilobites, brachiopods, bryozons, corals and gastropods preserved as limestone

Travel back some 570 million years to a time known as the Ediacaran and the picture is very different. Although there were large-bodied creatures that were possibly animals, they were entirely soft-bodied. Then, right at the end of the Ediacaran Period, the first animals with hard skeletons evolved, creating strange tubes, stacked cones, and other bizarre forms such as Namacalathus, which resembles a baby’s rattle!

Some of the first animals with skeletons, Cloudina and Namacalathus alongside the soft-bodied Ediacaran fauna. Reconstruction based on rocks from Namibia, Southwest Africa, from 543 million years ago. Image: Mighty Fossils.

 

In the following few tens of millions of years, in the early part of the Cambrian Period, a whole host of animals burst onto the scene baring their ‘teeth’, hiding in their shells, and bristling their spines. In fact, we can trace the origin of almost every kind of animal skeleton to this relatively short window of the Earth’s past.

In my research, I have compiled the evidence for how and when these skeletons first appear. Three key observations have emerged. First, skeletons evolved independently many times in different animal groups. Second, there is both direct and indirect evidence, such as exceptionally preserved fossils and trace fossils, for entirely soft-bodied examples of animal groups that later evolved skeletons. And lastly, the first animal skeletons are less complex and more variable than later examples.

Added to what we know about how living animals build their skeletons, this all points to one explanation: Animal skeletons evolved independently in different groups by utilising a common ‘toolkit’ of genes, inherited from their common ancestor but used in different ways in different skeletons.

In other words, the soft-bodied ancestors of animals with hard parts had inherited all they needed to build simple skeletons that were then honed into the array of shells, teeth, spines, plates and bones we see today. For these skeletal pioneers, armed with their genetic ‘toolkit’, the environmental and ecological pressures of the early Cambrian prompted the evolution of similar, but independent, responses to their changing world – when life got hard.

Murdock, DJE. 2020. The ‘biomineralization toolkit’ and the origin of animal skeletons, Biological Reviews, is available for free here.

Top image: Tiny fragments of early skeletons, shells and spines, from around 510-515 million years ago.

 

Excavating amber

First amber excavation in the El Soplao outcrop, Cantabria, N Spain in 2008. Credit IGME-UB.

By Dr Ricardo Perez-De-La Fuente, Research Fellow

Amber, or fossilised plant resin, is a unique material to learn about the history of life on Earth. Its incredible preservation and ability to capture life “in action” are well known thanks to the Jurassic Park saga, but fewer people know where amber is found, what it looks like in the field, and how it is gathered.

Cretaceous amber, about 130 to 70 million years old, is the oldest amber that provides abundant fossils, specifically insects and spiders. Ecosystems drastically changed during this period due to global greenhouse conditions and the diversification of flowering plants, among other factors. Amber from that time has been discovered in Lebanon, Spain, France, Myanmar, eastern United States, Canada, and northern Russia.

My research team and I carry out regular amber excavations in northern Spain, working in teams of six to ten people. The outcrops that we excavate are often located next to roads and highways because amber is typically uncovered during roadworks. Excavations take place during the summer or fall to try and minimise the risk of rain, and we usually embark on one field trip each year.

The goal is to recover as much amber as possible – usually a few kilograms – from the muddy and sandy sediments. These materials were transported downstream tens of million of years ago by heavy rain and river swellings from the forests where the resin was produced, before being finally deposited in near-shore areas.

Manual extraction of amber. Credit IGME-UB
Manual extraction of amber in the El Soplao outcrop, Cantabria, northern Spain in 2008. Credit: IGME/UB.

I find amber excavations quite romantic. In the field, amber has a dull appearance that makes it difficult to distinguish from rocks or woody remains. This is due to an opaque crust resulting from oxidation in the sediments and other processes.

This outer layer makes detecting potential fossils inside the amber highly unlikely while the excavation is ongoing. So, in the field we just gather as many amber pieces as possible, and hope for the best.

Only when amber is polished – or shows broken surfaces – does its distinct yellowish to reddish shine emerge, and any possible fossils within become evident. Some ambers are highly fossiliferous, while others are very poor in fossils.

Amber can be gathered by hand using regular tools such as hammers. However, the most efficient method to extract amber from soft sediments is with concrete mixers! This rather unsophisticated piece of equipment provides the best way to recover medium quantities of amber in the field.

We charge water and amber-bearing sediments into the mixer, and after stirring for a while amber floats to the top because it is less dense than muddy water. Then, the surface of the water containing the amber is poured into sieves, which separates even the tiniest pieces.

Amber pieces recovered in a sieve after washing
Amber pieces recovered in a sieve after having been “washed” from their sediment. First amber excavation in the La Manjoya outcrop, Asturias, northern Spain in 2017.

After fieldwork, many hours will be spent looking for fossils within the amber and preparing them. Gathering raw amber is just the first part of a process in unearthing the secrets held within – fragments of encapsulated time.

Top image: First amber excavation in the El Soplao outcrop, Cantabria, N Spain in 2008. Credit: IGME/UB.

A grasp of the past

by Ricardo Perez-De-La Fuente, research fellow

Few creatures look weirder – or are cooler, in my opinion – than mantidflies. There are around 400 species of these small predatory insects known worldwide – a scarce diversity by insect standards.

Like praying mantises, mantidflies have long ‘necks’ and forelegs armed with powerful spines and other structures used to hunt their prey with a sudden lethal grasp. The unfortunate victims become immobilised until they are meticulously eaten alive – not the best way to spend your last minutes on Earth!

Mantidflies belong to the Neuroptera order of insects and so aren’t actually related to praying mantises, but to insects such as lacewings and antlions.

A new paper that a colleague and I have published presents a new fossil mantidfly from Spanish amber that is important in understanding the evolution of their gripping – or raptorial – forelegs. The finding is presented in the open access journal Scientific Reports today.

Although the discovery has just been published, we excavated the new fossil during the scorching summer of 2010 in Teruel, northeastern Spain.

Amber excavations are very romantic – while they take place we carefully store the amber, piece by piece, into muddy plastic bags, remaining oblivious of what creatures are being unearthed because the amber surfaces have become opaque during fossilisation. Later, in the laboratory, the surfaces of the amber pieces are polished and screened for inclusions. Then a first glimpse is gained into what has remained frozen in time for millions of years.

It is only when the amber inclusions are carefully examined and studied that the implications of the specimens that were dug up years earlier start to be revealed. In this case, a specimen that was preserved in fragments, nothing spectacular at first look, ended up being truly exceptional.

Foreleg of Aragomantispa lacerata, showing powerful spines and other structures adapted to strike and hold prey.

Extinct true mantidflies, particularly those preserved in amber, are extremely rare. Our new fossil, pictured above at the top of the article, is 105 million years old, from the Cretaceous period. It currently stands as the oldest true mantidfly known in amber. The new extinct species, named Aragomantispa lacerata, has allowed us to compare the structures of the raptorial forelegs between extinct and extant mantidflies with an unprecedented detail.

Comparison between the foreleg spine-like structures of the new fossil mantidfly (up), with those from a close modern species (bottom).

Present-day mantidflies have forelegs with spines that bear minute cones at their tip. These cones are sensory organs that elicit the striking reflex and feel the prey’s movements once captured and restrained by the mantidfly’s tight embrace.

The forelegs of Aragomantispa lack these cones at the spines’ tip, instead having larger, icicle-shaped tips. We do not know how sensitive the mantidfly forelegs were in the Cretaceous, but the spines of at least some of these insects seem to be not as specialised as those from their present-day relatives.

Some mantidflies have smaller, reclined hair-like structures forming an edge on the leg’s surface opposing the spines. These reinforced edges create a scissor effect that stuns prey when the forelegs strike. Although Aragomatispa has these structures on the forelegs, they are also different in shape to those found on extant mantidflies.

Reconstruction of Aragomantispa lacerata striking at a hypothetical prey on a fern in the Cretaceous Spanish forest.

The fossil record offers the only direct means to assess when and how the traits characteristic of a given animal group originated in time. However, this kind of fossil evidence appears very occasionally. Our discovery shows that the foreleg spine-like structures of recent mantidflies were not fully developed in at least some of their Cretaceous ancestors.

The most exciting part is to think that this story and literally thousands more lie waiting to be discovered – or otherwise forgotten forever – buried underground.

How the sea cucumber lost its armour

By Imran Rahman, Research Fellow

You have probably heard of sea cucumbers. If you’re lucky, you might have seen one, if not in the wild, then perhaps in a nature documentary like Blue Planet or the children’s cartoon Octonauts. If you’re less lucky, you might have eaten one – they are most commonly described as slippery and bland in taste!

Despite their appearance, sea cucumbers are actually marine animals most closely related to sea urchins, rather than to worms or slugs. Over the past century palaeontologists have uncovered a range of ancient fossil relatives of modern sea cucumbers that allow us to piece together the story of how they evolved from armoured ‘tanks’ into the naked slug-like forms we see today. One such fossil is described in a new paper by my colleagues and I, just published in the journal Proceedings of the Royal Society B.

The fossil in question is 430-million-years-old, and it comes from a site of exceptionally-preserved fossils in England called the Herefordshire Lagerstätte. Herefordshire has produced many exciting discoveries over the years, from prehistoric parasites to an ancient ‘kite runner’. The new fossil is the first of its kind from this deposit.

Like all fossils from Herefordshire, the specimen was preserved in an egg-shaped nodule of rock. Because the rock has the same chemical composition as the fossil, it could not be studied with modern imaging methods such as CT scanning. Instead, it had to be studied by painstakingly grinding away the fossil, a few hundredths of a millimetre as a time, with photographs taken of each exposed surface using a digital camera. This allowed us to build up a dataset of hundreds of slice images through the fossil, which were digitally reconstructed as a 3-D ‘virtual fossil’ on a computer.

The 3D computer reconstruction revealed a very peculiar animal, about 3 cm wide, with 45 tentacle-like ‘tube feet’ and a large mouth surrounded by five teeth. The animal had a skeleton made up of numerous hard plates, which were composed of the mineral calcite. After studying this fossil and comparing it to other similar ones from the same time period, we were able to identify it as a species new to science. We named the species Sollasina cthulhu, for its resemblance to monsters from the Cthulhu universe created by author H.P. Lovecraft.

One of the most useful things about our 3D computer reconstruction was that it enabled us to study the inner features of the fossil, as well as the parts visible on the outer surface. This revealed internal soft parts that had never previously been described in this group of fossils. In particular, it allowed us to see an internal ring-like structure within the main body cavity.

3D reconstruction of Sollasina cthulhu. Left-hand image shows part of lower surface. Right-hand image shows same view with outer surface partly transparent to reveal inner ring (in red). Credit: Imran Rahman, Oxford University Museum of Natural History

We interpreted this inner ring as part of the water vascular system – the system of fluid-filled canals used for feeding and movement in modern sea cucumbers and their relatives, such as sea urchins and starfish. In life, the ring was connected to the large tube feet, which were filled with seawater. Most of these tube feet were used for crawling over the seafloor, with those nearest the mouth used for capturing food. The teeth could cut and crush food items, which were then eaten by the animal.

Life reconstruction of Sollasina cthulhu. Credit: Elissa Martin, Yale Peabody Museum of Natural History

To work out the evolutionary relationships of Sollasina cthulhu, we assembled a list of characteristics for various fossil and modern sea cucumbers and sea urchins. We analysed this matrix using several computational methods to determine how these different animals were related to one another. The results confirmed that Sollasina cthulhu and closely-related forms were ancient relatives of modern sea cucumbers. This allowed us to reconstruct the early evolution of sea cucumbers, back to their shared common ancestor with sea urchins, over 450 million years ago. Our study demonstrates this was a story of loss, with fossil sea cucumbers becoming progressively less armoured as they evolved into modern forms.

This discovery has greatly improved our understanding of sea cucumber evolution, but several questions remain. One intriguing question is when and how did sea cucumbers lose their teeth, and did these evolve into any features seen in living sea cucumbers? Future study of existing and new fossil sea cucumbers and sea urchins will help to answer this and other intriguing questions.