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.
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.
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
Elsa Panciroli recently joined the Museum research team as an Early Career Leverhulme Research Fellow. Elsa is a Scottish palaeontologist, whose studies focus on the early evolutionary origins of mammals, working extensively on fossils from the Isle of Skye. Here she tells us how her work will combine studies of mammal evolution with stunning new fossil finds from Scotland.
We are mammals. This means we share a common ancestor with creatures as different as hippos, opossums and platypuses. All of us are united in one taxonomic group by a suite of characteristics in our bodies, but principally, that we feed our young on milk. Every mammal from a baboon to a blue whale produces milk for their offspring, and this makes us unique among animals alive on Earth today.
But not all mammals bring their young up in the same way; raising a kitten is nothing like raising a kangaroo or a platypus. Kittens are born stumbling around with their eyes closed, while platypus babies are laid in eggs – yes eggs – and when they hatch they look like little scampi. Both are underdeveloped at birth or hatching, but that’s nothing compared to kangaroos. They leave the womb only millimetres in length, and wriggle their way like living jellybeans toward a teat in the marsupial pouch, where they latch on. Only after two months of milk-drinking are they able to hop for themselves and leave the pouch.
The different ways that mammals are born and grow is a huge area of scientific research. But there are still some major questions to answer about the evolution of these growth patterns. When did the ancestors of mammals stop laying eggs? Were they born defenceless, or able to fend for themselves? How quickly did they grow up and how long did they live?
Over the next three years at the Museum, I’ll be looking for evidence in the fossil record to help us try and answer some of these questions. I’ll study living mammals to understand how they are born and grow, combining this information with data from some of the amazing fossils being found on the Isle of Skye. With collaborators in South Africa I’ll try and work out how the ancestors of mammals developed, and what this means for the bigger picture of the origin of mammals as a group.
Alongside my main research I hope to share lots of stories about our fossil past through the museum’s fantastic public engagement programme. I’m also very active on social media, and I write about science for online and in print publications. So if you see me on your next visit to the building, or find me online, feel free to ask about my research! I look forward to seeing you, and sharing more about the elusive and exciting origins of mammals – and ourselves.
When the campaign to build the Museum was launched, science at Oxford was understood as natural theology. By the time the Museum opened in 1860, a new secular approach to science was on the rise.
In this last episode of the Temple of Science podcast series we see how the art and science of the Museum responded to the challenge posed by Charles Darwin’s theories of evolution and natural selection, and the scientific naturalism that they epitomised.
Worms, fish and … Greenland? Hugely different topics which all have one thing in common – the Museum’s First Animals exhibition online lecture series. Running every other Wednesday from May until September 2020, this series provided a fantastic insight into a wide range of topics about how the first animals lived, died, and are studied. And illustrator Rachel Simpson tells us how she drew her way through them all…
I came across this lecture series just before the first talk and I knew I had to sign up. Drawing along to lectures is a hobby I seem to have developed in the past few months as we went into lockdown and didn’t have much to do. It’s the perfect combination for me – an opportunity to listen to interesting topics and brush up on my live drawing skills at the same time. There’s no pause button, there’s no asking the webinar speaker to just go back a few slides and hold on a minute whilst I draw; it’s fast paced, it’s inspiring and it’s a great way to just create art.
I’ve done some illustration work with the Museum before so I knew that it was going to be fun. In 2018, I worked with Dr Jack Matthews illustrating Ediacaran Fossils as part of a collaborative university project between the University of Plymouth and the Museum. I was also lucky enough to be able to go to Newfoundland and see some of the fossils myself, again with Jack. This was such an incredible opportunity and opened up a whole new world of science/art collaborative work which I didn’t know about before.
The First Animals series kicked off with Jack’s talk titled Don’t walk on the rocks! – an interesting insight into how protective “Barma Booties” (some rather funky socks worn to protect fossil sites such as Mistaken Point, Newfoundland) might actually be damaging to the fossils they’re meant to be protecting. Having been to Mistaken Point myself and worn these socks, it was interesting to hear about their possible impact and to learn about the experiments conducted to prove this fact.
Of course, at the same time as Jack was talking, I was scribbling away in my sketchbook trying to form some sort of visual response to the talk. At the end of the hour I’d managed a portrait of Jack and a family of Barma-Booted tourists trampling on the fossil site. It was a start. The beginning of my lecture drawings and a point at which I can retrospectively say started a new hobby.
Over the following weeks we heard about worms from Dr Luke Parry; 3D reconstruction from Dr Imran Rahman; The Chronicles of Charnia by Dr Frankie Dunn; and the first animal skeletons from Dr Duncan Murdock. Luckily for me, all the speakers kindly included photos and descriptions of the topics they were discussing which meant that I was never short of visual inspiration for my drawings. After all, it’s hard to try and draw an annelid worm if you’ve never seen one before.
I love to look at the fossils being discussed and then try to draw a little character or creature inspired by them. They’re not scientifically accurate, nor are they always anatomically correct, but they have character and begin to bring to life the essence of something that’s been dead for many millennia. The fossils are obviously stone-coloured so I take as many liberties as possible when it comes to colour. I like to make them as vibrant and colourful as I can, so although they probably didn’t look like that, that’s how I like to think they looked.
Some fun little beasties from Dr. Imran Rahman’s talk.
Charnias galore! They come in all different shapes and sizes.
Small filaments which could have joined all those Charnia together.
Shells, bones and teeth from Dr. Duncan Murdock’s talk drawn in Tombow brush pen and Posca Pen.
Within my wider practice I like to use stamps as the basis of my illustrations. These however, are time consuming to make and therefore not very suitable for when I’m drawing along to lectures. As a result I’ve found myself using brush pens and pencils to make my lecture illustrations. If you’re interested in art, or thinking about getting into art, brush pens will be your best purchase. They create a wonderful quality of line and are quick and easy to use. Whereas a ballpoint pen will give you one line of a certain weight and thickness, brush pens are versatile and depending on the pressure applied, the line quality will change.
For the first few lectures I only used brush pens, but later on I decided to use coloured pencils as well, to add depth to the drawings. As I got more used to drawing in lectures I found that I was making more illustrations per talk. Early on, I managed to finish maybe a double page in my sketchbook but towards the end of the series I was filling four double pages! It’s amazing what a little bit of practice can do.
As the weeks went by the talks continued and we heard about the evolutionary origin of animals from Museum director Professor Paul Smith; an introduction to taphonomy, the study of fossilisation, by Professor Sarah Gabbott; and how the first animals moved by Professor Shuhai Xiao.
During this time I became a lot more confident drawing the specimens; looking back I can see that this was the period in which my work developed the most. My drawings began to have more character and life. The landscape drawings were slowly becoming more realistic and detailed. This was great news for me as this whole endeavour began as a way to practice my drawing skills in a timed environment.
Paul Smith’s lecture has to be my favourite of them all. He gave a wonderful talk all about the Evolutionary Origin of Animals and talked us through his fieldwork expedition to Greenland. How I would have loved to have been on that trip!
How I would have loved to have been on this trip! Drawings of Professor Paul Smith’s fieldwork to Greenland.
Some of the weird and wonderful fossils Professor Paul Smith found on his trip.
One of my favourite drawing from the lecture series! Drawn with Tombow brush pens and Polychromo pencils.
It was during Paul’s talk that I made one of my favourite drawings from the series – the plane –and coincidentally it was also at this point that I bought myself some new polychromo pencils. I started using these pencils in my illustrations on top of the Tombow brush pens. The pencils added a softer layer on top of the solid base colour from the brush pens and meant that I could add more details, shading and most importantly, the characterful eyes I love to add to my drawings.
Fish and animal studies from Professor Sarah Gabbott’s introduction to taphonomy, the study of the processes of fossilisation.
Imagine being the owner of this house and being told there were found fossils on your roof! Drawing from Professor Shuhai Xiao’s talk.
Buoyed by this development in my drawings, and some lovely responses to my work on Instagram and Twitter, I raced through the next few weeks of talks and made twelve pages of drawings over the next four talks. Professor Derek Briggs told us all about extraordinary soft-bodied fossils; Professor Gabriela Mángano told us about the trace fossil record; and Professor Rachel Wood gave us her thoughts about what triggered the Cambrian Explosion.
Another favourite drawings from the series, drawn from Professor Derek Briggs’ talk.
Close up of drawing from Professor Derek Briggs’ talk.
Trace fossil studies drawn in Tombow brush pens and Polychromo pencils.
The last drawings from the series from Professor Rachel Wood’s talk.
Another of my favourite drawings from the series was from Derek Briggs talk about extraordinary soft-bodied fossils. Here, I made a small series of drawings based on some of the animals mentioned in the talk and as soon as I’d finished drawing them I wished that they were real and that I could pop them in a fish tank and keep them as pets. These drawings got the best response on social media too and it’s wonderful now to look back and compare these drawings to the work I was creating at the beginning of the series.
The First Animals series may be over but keep your Wednesday evenings free because there are more talks to come! The next series, “Visions of Nature”, starts on 8 October so make sure you join us then! A huge thank you to all the speakers, to Jack for hosting and to the Museum for running the events.
With the noises of the hectic morning commute temporarily silenced, it has never been a better spring to enjoy the sounds of the dawn chorus. If you are able to get out early it’s a great way to reduce some of the stresses of lockdown. But if you can’t, or would rather have a lie-in, here we bring a little of the dawn chorus to you.
The video above shows the beautiful grounds of Harcourt Arboretum, a site a few miles outside Oxford that is part of Oxford University’s Gardens, Libraries and Museums. The chirruping, tweeting soundtrack was recorded at the start of the pandemic lockdown, and is an excerpt from 50 minutes of uninterrupted dawn chorus which you can listen to in full here (recommended background while WFH!):
The enveloping sound of the dawn chorus is an ensemble piece, but who are the individual players? To hone your birdsong identification skills and practice picking out individual songs of some common British birds, Andy Gosler at the Edward Grey Institute for Ornithology has put together this beautiful resource.
So now we’re in the zone, let’s find out a little more about the dawn chorus and how it’s made.
A sense of dawn Why are so many birds singing at dawn and not at another time of day? There are several good reasons which may explain this.
At dawn, there are fewer other environmental noises cluttering the airwaves and the air density and temperature allow sound to travel further. Many migrant birds arrive in the UK overnight and early morning, and those that are ready to breed begin looking for mates and territories early in the day. So singing at this time stakes a clear claim to new arrivals and announces that the territory is already taken.
For insectivorous birds and those that use sight to find food, dawn is the least profitable time to search. Insects are more dormant in colder temperatures and food less easy to spot in dawn’s lower light levels and early morning mists. It’s a better use of time and energy to sing!
But why spring? What triggers birds to start singing? It clearly makes sense to breed at this time of year when there is a steady supply of food, as insect population growth coincides with the re-growth of the plants that feed many insects.
But the real trigger is day length. Increased light boost hormones in birds that spark incredible physiological changes. Unlike humans, birds have an amazing ability to reduce and increase the size of various organs according to their use, carefully regulating the amount of energy expended by those organs.
Shifting sounds As hormone levels increase, not only do birds’ sexual organs increase in size ready for the breeding season, but the part of their brains dedicated to sound processing and sensitivity also increases, meaning that birds’ hearing abilities fluctuate throughout the year.
Imagine not being able to recognise what people were saying or who was talking in winter, then suddenly being able to pick out every minute difference in tone, volume and timbre in spring! When you listen to the cacophony that is the dawn chorus, this is exactly what each bird is doing – recognising each individual and its territorial and breeding condition – and many birds show less acuity for this outside the breeding season.
Sound location also improves. Humans have relatively large, wide heads and this allows us to judge the direction a sound is coming from by detecting the slight differences heard by each ear. With their tiny heads, birds cannot do this when their heads are still, so they move their heads around a lot to help locate sounds.
You might be thinking that with such sensitive hearing birds would be in danger of going deaf during a raucous dawn chorus. But they have another adaptive trick up their sleeves. Inside the inner ears are tiny cilia, or hairs, that detect the vibrations of sound. In mammals, these hairs gradually diminish over time and don’t grow back, but birds have the ability regrow cilia throughout their lives!
Hidden music Birds are also able to process birdsong much more quickly and fully than we can, hearing things that our brains are just too slow to cope with. Whilst we may love the musicality of the dawn chorus, we are actually missing many of the individual notes.
Sonograms of bird songs show that where humans often hear just a couple of notes there may be several more emitted at rapid speed.
How do they do it? We sing by passing air over flaps of skin in our sound-producing organ, the larynx, a bit like blowing over a piece of grass trapped between your thumbs. But birds have separately evolved another and more impressive way of singing. They don’t just have one organ to produce song, they have two – called syrinx.
Syrinx are more like drum skins that can be tightened or loosened by muscles as sound passes over them. They can be operated independently or together enabling a single bird to sing a chord of several notes at the same time in harmony with itself!
Time to tune in to the dawn chorus and marvel at the complex, beautiful phenomenon of birdsong…
Vision is among the most important innovations in animal evolution. The ability to see predators, prey, mates, and the environment transformed the way animals interact with each other and the world around them. Eyes can take many different forms, but this month saw the description of a visual system unlike almost any other known to science, found in a brittle star called Ophiocoma wendtii.
Brittle stars are marine invertebrates related to starfish. They have long, slender arms connected to a central disk, but no head, no brain, and – so we thought – no eyes. But recent experiments have shown that some brittle stars are able to see the world around them.
Ophiocoma wendtii is a common species found throughout the Caribbean Sea and the Gulf of Mexico. If you rummage around in coral rubble in shallow water, you’ll probably find Ophiocoma hiding underneath rocks and other debris, sheltering from their fishy predators. It has beautiful bright red tube feet (small, water-filled tentacles) and a neat party trick: it changes colour. During the day, the animals are a deep reddish-brown colour, but after dark they become beige with dark stripes.
For more than thirty years, O. wendtii has been something of a mystery to scientists like myself who are interested in animal vision. It’s covered in light-sensing cells – thousands of them – and it hates being exposed to bright light, quickly dashing for cover if possible. However, it’s possible to head for dark, shadowy places without vision; you only need to be able to tell that one direction is brighter than the other. So, with a team of colleagues from Germany, Sweden and the USA, we set about giving the brittle stars an eye-test.
We know that when they’re exposed to sunlight, O. wendtii try to hide underneath nearby rocks or other objects, so we designed a circular arena with a stimulus printed on one side – the idea is that the stimulus might resemble an object under which the animals can shelter, and the animal will move towards it.
We ran three experiments, changing the stimulus and background of the arena in each to test whether the brittle star can just see relative light or dark areas, or whether it can resolve finer points of contrast. To my surprise, O. wendtii moved towards the stimuli in all three experiments significantly more frequently than expected by random chance, as you can see in the video below. This was super exciting, as it represents not only the very first evidence of vision in these animals, but the second known example of any animal that can ‘see’ without having eyes (the first is a close relative, a sea urchin).
While O. wendtii is known to shelter during the day, we were also curious to test its behaviour at night. Running the same experiments again in natural darkness, we found that animals no longer moved towards any of the stimuli. There could be a whole number of reasons behind this, so we devised tests that eliminated several possibilities, and were left with a remaining explanation that the animal’s colour-change between night and day was somehow responsible.
Colour-changing in the brittle star is controlled by the expansion and contraction of cells, called chromatophores, that are filled with pigment granules. These sit inside pores in the skeleton, alongside the light-sensing cells. During the day, the chromatophores expand, pushing up through the pores and spreading over the body surface. The pigment is spread over the outside of the animal, which looks dark brown as a result. During the night, the chromatophores contract, bringing all the pigment granules back inside the skeleton and giving a paler appearance.
We thought that during the day the pigment granules surrounding the light-sensing cells might block light reaching them from most directions. To test this, we constructed digital models of the visual system, creating 3D models of the light-sensing cells, the skeleton, and the pigment granules.
We found that in light-adapted systems, those with pigment, light could only reach the sensory cells from an angle of around 60° out of 360° which, though probably very coarse, could support vision. By removing the pigment from the models, vision was made impossible, as light could reach the sensory cells from too many different directions. It looked as though it was the chromatophores that made all the difference.
This is the first proposed example of whole-body colour change enabling and disabling vision in any animal, and raises many new questions about image formation and information processing. There are exciting parallels with the only other example of ‘extraocular’ (=without eyes) vision, the sea urchin we mentioned earlier: these sea urchins can also change colour in response to light levels, using similar chromatophores. Have they independently evolved a similar trick?