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

On the trail of the evolution of mammals

Woman sitting on top of a large, layered rock formation

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.

Wareolestes rex is a Middle Jurassic mammal, illustrated here by Elsa Panciroli

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?

The Rock Hyrax (Procavia capensis) is a terrestrial mammal native to Africa and the Middle East

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.

Follow Elsa on Twitter at twitter.com/gssciencelady.