Skye's Ancient Ecosystem: non-technical summary

Last month I published a non-technical summary of the scientific paper describing Scotland's new dinosaur discovery, StEiggosaurus. This month I'd like to do the same for another of my papers: Diverse vertebrate assemblage of the Kilmaluag Formation (Bathonian, Middle Jurassic) of Skye, Scotland, which came out online at the end of July 2020. It summarises discoveries made to date from part of the rock series on the Isle of Skye - the Kilmaluag Formation, one of the most fossiliferous sites in the UK for vertebrate animals - and compares this with other sites around the world.

Below is a non-technical summary of the paper. No matter your background you can find out about the scientific discoveries being made in Scotland!

Introduction

The Middle Jurassic (164-174 million years ago) is a pivotal time for many land-living animal groups. Not only is there an expansion in the number and kinds of animals (including dinosaurs), but we can also trace the origins of groups that are still alive today. These include mammals, squamates (lizards and snakes) and amphibians. To understand how these groups emerged, and the evolutionary changes that led to their success and diversity in later time periods, we need to study their fossils. 

Looking around the world, the fossils of Middle Jurassic land animals are quite rare compared to other parts of the Jurassic, and the Cretaceous which followed. Some of the best-known examples come from China, Russia, and the British Isles. In the UK, the fossils from sites in Oxfordshire and Gloucestershire in England have been among the most studied and celebrated to date. They have been especially rich in very small backboned animals, the exact groups that scientists are so keen to understand because of their long-standing role in Earth's ecosystems.

There is a series of rocks on the Isle of Skye collectively called the Great Estuarine Group. It is one of the most fossiliferous rock layers in the UK, and as such is legally protected as a SSSI (Site of Special Scientific Interest) and through Scotland's new NCO (Nature Conservancy Order). All work on these rocks requires a permit, and fossils can only be collected for scientific purposes. Work has been carried out on the fossils in these rocks in the Southern part of Skye since they were first discovered in 1971 by Michael Waldman. Since that time many different researchers have worked there, notably Robert Savage (University of Bristol), Susan Evans (University College London) and Paul Barret (Natural History Museum, London). In the last decade Stig Walsh (National Museums Scotland), Roger Benson (University of Oxford), Richard Butler (University of Birmingham) and I have been the main team working on the Kilmaluag Formation.

Our research shows that the fossils from this layer of rocks are globally significant in terms of their completeness and preservation. This makes them vitally important for ongoing studies into the origins of multiple animals groups, and places these Scottish rocks among the most important Middle Jurassic localities in the world.

Geology of the Kilmaluag Formation

The Kilmaluag Formation is one of seven rock formations in the Great Estuarine Group, found in the Inner Hebrides of Scotland. It dates to the Bathonian, around 166 million years ago. This series of rocks captures a changing landscape as the area lifted and fell due to geological processes, causing the land to dip above and below sea level. This periodically created shallow seas, or more terrestrial lagoon environments and deltas. Much later in the Palaeogene around 55 million years ago, these rocks were covered by volcanic eruptions, which also cut through and heated the rock in places. Now the Great Estuarine Group is only visible where the volcanic rock has been eroded by water and ice to reveal the older rocks underneath. This happens predominantly along the shoreline.

The Great Estuarine Group, which includes the Kilmaluag Formation (circled in red).

The Kilmaluag Formation is found on the Isles of Skye, Eigg and Muck, and is up to 25 metres thick. It's named for the village of Kilmaluag on the north coast of Skye, but although you can find some of these rocks there, the largest exposed parts of the Kilmaluag Formation are on the Strathaird Peninsula in the South of the Island. The rocks are Late Bathonian in age, and they are unique because unlike the rest of the Great Estuarine Group, they represent an almost entirely freshwater environment. We know this from the numbers of freshwater organisms preserved in them, including small crustaceans called ostracods (the Kilmaluag Formation used to be called the Ostracod Limestone).

In the north of Skye, the Kilmaluag Formation mostly comprises sandstones, whereas in the south of Skye and on Eigg and Muck, it is mostly limestone. There are cracks running through some of the beds, showing us that there were periods when the sediments dried out completely and cracked, before being filled-in during wetter climate cycles. The presence of muds with lots of clay and carbonates tells us this was once a landscape covered in freshwater lagoons. The layers that yeild the most vertebrate fossils were probably just above the shoreline, and dried out from time to time before being flooded again.

Fossil Plants and Animals from the Kilmaluag Formation

Plants

There hasn't been much work on the plant fossils from the Kilmalag Formation. There are some small bits of bark and stem visible in the rock, but they are very broken up. A study carried out in 1991 looking at the small spores left by plants in the fossil record from Skye, found pollen in the rocks on the north of the island. The pollen mostly came from plants like conifers, cycads (gymnosperms) and ferns (pteridophytes).

Invertebrates

There are lots of invertebrate animals in the Kilmaluag, mostly in the form of ostracods (Darwinula and Theriosynoecum), conchostracans (Anthronestria and Pseudograpta), gastropods (Viviparus) and bivalves (Unio). There are some trace fossil burrows that are thought ot have been made by some kind of crab or shrimp. 

I discovered the first insect fossils from the Kilmaluag in the north of island in 2017 - mostly beetle wing cases - and more have been found since then. They're currently being studied by researchers at National Museums Scotland in Edinburgh, and the Huntarian in Glasgow.

Fish

A lot of fish fossils are found in the Kilmaluag Formation. Fossil sharks, Hybodus and Acrodus are commonly represented by their teeth, and they are some of the only non-marine Jurassic Acrodus fossils in Europe, and youngest in the world. The scales of other kinds of fish have also been found, and there are also some skeletons which are now being studied.

Amphibians

There are two species of salamander known from the Kilmaluag Formation: one called Marmorerpeton, and the other known only as 'Kirtlington salamander A'. Both of these were previously found at the English fossil locality called Kirtlington Cement Quarry, in Oxfordshire. Marmorerpeton is a relatively large (around 30 cm in length) aquatic salamander. It was previously only known from just a few scattered pieces of bone, but there are now several partial skeletons from Skye, which are being studied by our group and our collaborators. It's significant because it belongs to the very earliest group of salamanders that evolved in the Middle Jurassic, so knowing more about its skeleton will help us understand the emergence of the whole group.

Another amphibian found on Skye is Anoualerpeton. It belongs to a group called the albanerpetontids, which went extinct just 2 million years ago. There are no frogs known from the Kilmaluag Formation at the moment - we'll keep looking!

Lepidosaurs - 'Small Reptiles'

The lepidosaurs are the taxonomic group that include snakes, lizards and the tuatara (found in New Zealand). Although often colloquially referred to as 'small reptiles', some of them can grow very large. Their main uniting trait is that they have overlapping scales on their bodies. 

There are lots of early ancestors of lepidosaurs in the Kilmaluag Formation - these fossils are really important for our knowledge of the evolution of this animal group, which is now common throughout the world. Most of these lepidosaurs are known from jaws and some pieces of the skeleton. One of the most common on Skye is Marmoretta, which is now known from lots of jaw bones as well as a partial skeleton - the most complete in the world to date. Other lepidosaurs include Balnealacerta, Bellairsia and Parviraptor. Partial skeletons of these animals are all currently being studied by our group and our collaborators.

Turtles

The Kilmaluag Formation yeilded Scotland's very own Jurassic turtle: Eileanchelys waldmani. It was found in 2004, and represents one of the earliest aquatic turtles in the fossil record, and one of the very few known from this time period around the world. It belongs to near the base of the family tree of living turtles, so it's anatomy helps us understand the evolution of turtles in the time of dinosaurs. Turtle bones are relatively common in the Kilmaluag Formation.

A selection of fossils from the Kilmaluag Formation (clockwise from top left): the teeth of a shark; the jaw of a mammal; the jaw of a lepidosaur' the toothof a dinosaur; the head of a turtle; the tooth of a close mammal relative.

Choristoderes

Choristoderes became extinct around 20 million years ago, but they had their roots some time prior to the Middle Jurassic. They were semi-aquatic reptiles, and mostly quite small (hand sized). Their exact relationship to other reptiles is not certain, partly because of a lack of more complete fossil material. The choristodere Cteniogenys is found on Skye, including bits of the skeleton and a small skull. This is the most complete material known for this animal, and is currently being studied to see what it reveals about the group.

Unidentified Small Reptiles

There are at least four unidentified types of reptile in the Kilmaluag Formation, but unfortunately they don't have any of the features needed to place them in their own genus or species. Hopefully future discoveries will make it possible to name them, and tell us more about what group they belong to.

Crocodiles

A partial skeleton was found in the Kilmaluag Formation and described in 1996. It includes parts of the limbs, ribs, vertebrae and osteoderms, the hardened scales that made up the skin. Some teeths and other bits of crocodile have been found, but mostly not figured or described yet.

Pterosaurs - Flying Reptiles

There are two pterosaur skeletons known from the Kilmaluag Formation, both partial. These are the first flying reptiles to be found in Scotland, and are currently under study.

Dinosaurs

Very little dinosaur material has been found in the Kilmaluag Formation so far. A single tooth belonging to a sauropod, a tooth belonging to a theropod, and an incomplete limb bone, are all that is currently known. Footprints have been found in the northern part of the island, including large and small theropod prints which might represent adults and their young.

Mammals and Kin

The first Jurrasic mammal from Scotland was found in the Kilmaluag Formation in 1971, Borealestes serendipitus, along with the first close relative to mammals, an animal called a tritylodontid. Since then many different early mammals have been found on the island. 

A jaw from Borealestes, found a few years ago. Only the tips of the teeth were visible on the surface, the rest was seen and studied by CT scanning the rock.

Borealestes belongs to a group called the docodontans, which are an early offshot of mammals. They interest scientists because we've dicovered in the last 20 years that despite being from such an early part of the mammal tree, they had evolved very specialised adaptations to their environment - something we thought was exclusive to more recent mammal groups. The partial skeletons of several docodontans are currently under study (a new paper on this should be out very soon!) and should tell us more about their evolution.

Another early-branching mammal is Wareolestes, which is known from Skye from a single jaw. The jaw had replacement teeth just emerging, indicating it was a young animal about to replace it's milk teeth. Other mammals discovered from the Kilmaluag Formation are closer relatives to living groups. They include Palaeoxonodon, which is known from a near-complete jaw found in 2015 (and some other pieces of jaw). The specimen told us that many of the species identified previously from Oxfordshire based on individual teeth, were actually the same animal. The differences in tooth shape were due to the position of the tooth along the tooth row, rather than being fundamental differences between species. This has a knock-on effect for our estimates of how diverse the mammals were in this time period. 

My collaborators and I are currently studying some partial skeletons of several species of mammal from the Kilmaluag Formation.

Comparisons With the Rest of the World

Looking at the animals found on Skye and comparing them to other localities globally, we can see that Skye has a really diverse number of vertebrate fossils. Many of the same species are found at Kirtlington Cement Quarry in Oxfordshire, which dates to the same time period in the Middle Jurassic. But the fossils from Skye are generally more complete than those in England, and so provide new information about the anatomy of these creatures. In many cases, the fossil material found on Skye is the most complete example of these species, especially the small reptiles, salamanders and mammals.

Some groups known from England haven't been found yet on Skye, including frogs, the group of lepidomorphs called rhynchocephalians, and haramiyid and multituberculate mammals. It might be that the English site represents a slightly different environment where these animals didn't live, but it could also be that differences in how we collect fossils on Skye (see Collecting below) account for these differences.

Similar animals are found in Middle Jurassic sites in Russia (Itat Formation) and Morocco (Guel el Ahmar Fauna). The similarities with Russia are strongest, except that there are haramiyid and multituberculate mammals in Russia (and not Scotland, yet). The Middle Jurassic of Morocco is still only poorly known, but it is interesting that there could be similarities, because it was separated from Skye in the Middle Jurassic by the growing Atlantic Ocean. Hopefully more material from this and other sites from the Southern continents will provide more information.

The Jurassic fossils of China are certainly the most spectacular examples of their kind in the world. Although much younger than those on Skye (late Jurassic in Age), they include some of the same groups, such as  small reptiles, pterosaurs, theropod dinosaurs and the docodont mammals. There is a much higher diversity of dinosaurs in China, but there are more small reptiles in Scotland, and similar numbers of mammal species. Most of the fossils from China are exceptionally complete, but they are preserved and collected quite differently from those in Scotland. Their spectacular appearance can give the impression that China held an ultra-diverse and unusual collection of animals with lots of unique specialisations. However the same types of animals are known from elsewhere, they are simply much less complete athan those in China.

Other Late Jurassic sites include the Morrison Formation (Late Jurassic, USA) and Alcobaça Formation (Guimarota, Portugal). Collecting has taken place in the Morrison Formation for a long time, and the list of animals found from those layers is huge. As in Scotland, choristoderes, fish, salamanders, crocodiles, pterosaurs, dinosaurs and mammals are known from the Morrison Formation, but there are lot more species known than in Scotland. The Alcobaça Formation in Portugal also has some similarities with the Kilmaluag Formation: similar species of fish, small reptiles and mammals are known. Both sites also have crocodiles, pterosaurs and dinosaurs, but in greater numer os species in Portugal to date. 

The Purbeck Formation in England is another site worth comparing: it is Late Jurassic to Early Cretaceous, and is very diverse, being one of the most diverse vertebrate fossil Formaton in the UK. Although similar groups of animals are represented there, there are very few crossovers with the Kilmaluag in terms of the actual species - except for some of the fish, and the squamate, Parviraptor. 

One interesting thing when comparing the geologically later sites like the Morrison, Alcobaça  and Purbeck Formations, with the older Kilmaluag Formation, is that the mammal groups change noticably. In these later Formations there are fewer of the early-branching groups of mammals like docodontans, and more members of more modern groups, including multituberculates and haramiyidans.

Collection Methods and Potential Biases

Of course when comparing the Kilmaluag Formation animals with other sites, we have to bear in mind the methods used to find and extract fossils. These methods effect what palaeontologists find at a site, and so must be taken into account when assessing the fossil assemblage compared to other locations. In the Kilmaluag Formation fossils are found only when they are visible on the rock surface. They are extremely difficult to remove from the site due to the nature of the rock and the location (and they are also only collected when deemed scientifically valuable, to limit our impact on this sensitive area). Once extracted, they can mostly only be studied by CT scanning them, and are not easily removed from the rock with acid.

At most other sites, people actively dig the layers to find fossils. They are easier to remove, and can be prepared from the rock and therefore studied much more easily. In many cases, rock can be bulk processed: dissolving the rock and seiving out the contents. In this way, it's possible to find a lot more fossils, which increases the likelihood of discovering new species and groups. The sites in Oxfordshire and Gloucestershire produce lots and lots of single teeth and bones.

However there is a plus side to the less copious discoveries from Scotland. The fossils in the Kilmaluag Formation - especially of the crucial, small-bodied animals - are often much more complete. Whereas bulk processing means most fossils are reduced to shrapnel, the method in Scotland of studying fossils with CT scanning allows us to keep the skeletons in their original position, and study them in three-dimensions, digitally. This is a huge advantage for the amount of information we can gain from each specimen. Most of the material found to date, although not from new species, represent the most complete examples of these animals known, particularly for the small reptiles, salamanders and mammals.

Looking at the collecting done by the three main groups that have worked on the Kilmaluag Formation since 1971, there are some interesting differences. Collecting in the 1970s resulted in more mammal material, whereas collecting in the early 2000s produced a lot more fish. Our work in the last decade has produced the most lepidosaur material. Overall, mammals and their close relatives, and lepidosaurs, are the most commonly found vertebrate fossils in the Kilmaluag Formation.

The numbers of different groups found in the Kilmaluag Formation is likely to shift as we identify more of the fossils we've collected, and publish those that are currently in the pipeline.

Conclusions

It's clear that the Kilmaluag Formation contains the richest vertebrate fossil material in Scotland, and is one of the most diverse and important in the world. Although at first glance it may seem less diverse than other Middle to Late Jurassic sites around the world, this is likely more to do with the way in which fossils are found, collected and studied, which limits the volume of material we can process. However, what we do have is extremely complete and provides a wealth of new information on the animals of this time period.

Comparing sites around the world with that in Scotland, we can see the distribution of animal groups in this time period, helping us understand ecosystems over 150 million years ago. There are many more fossils from the Kilmaluag Formation being studied and to be published in the coming years. This shows that protection of the shorelines of the Isle of Skye is vital to safeguard our nation's geological heritage, preserving it not only for science, but for the public, and the generations to come.

Eigg Dino Paper: non-technical version

I’ve had a few requests for a non-technical summary of the paper describing the recent discovery from the Isle of Eigg. Our paper, titled First dinosaur from the Isle of Eigg (Valtos Sandstone Foration, Middle Jurassic) Scotland, was published in the scientific journal Earth and Environmental Science Transactions of the Royal Society of Edinburgh in August 2020. There are 13 co-authors, each bringing their own specialism to the mix, with myself as lead author. 

But scientific papers are often a bit opaque for non-specialists. So below I've written a walkthrough of the science, written for the general public. In it, I tease out the details of our discovery and research for everyone to enjoy. If you have any Qs, please ask!

Introduction

The Middle Jurassic (174-164 million years ago) is a special time in the evolution of life on Earth. Many groups appeared at this time or shortly before, and they split into lots of new families, and exploited new ways of life. This evolutionary pattern is also true for dinosaurs. However, scientists struggle to understand how and why this happened because fossils from the Middle Jurassic are so rare. Almost five times as many fossils are known from the Late Jurassic as the Middle! As a result, every Middle Jurassic fossil is a vital clue to life at this time, and scientifically significant.

Although dinosaurs have been found in Scotland already, all of them have come from the Isle of Skye. This is because there are fossil-rich Jurassic rocks on the island dating to around 166 million years ago. As well as dinosaur limb bones, teeth, and footprints, scientists have found fossil crocodiles, turtles, pterosaurs, mammals and marine reptiles, as well as invertebrate fossils like ammonites and belemnites.

The Isle of Eigg, which lies south of Skye in the Inner Hebrides (west coast of Scotland), is also known for its Jurassic fossils. However, these are all from marine animals and mainly comprise reptiles (like plesiosaurs), fish, and sea-living invertebrates. Fossils have been found on Eigg since the early 19^th century, but in 200 years of searching no-one had ever found terrestrial animal fossils.

Our paper describes the first dinosaur bone found on Eigg, which I discovered during National Geographic funded fieldwork by the University of Edinburgh in 2017. Our small team was given permission to work on the Island by the Isle of Eigg Heritage Trust. Eigg is owned by the residents, so we had to seek their permission to work there. We found the bone on the shore where there are a series of rocks called the Great Estuarine Group. This is the same group that yields fossils on Skye. It includes many different layers formed under different conditions: some when the Inner Hebrides was a shallow sea, and others from lagoons and deltas when the land was just above sea-level. The Eigg dinosaur was in a layer called the Valtos Sandstone Formation, which was formed on an ancient Middle Jurassic shore where rivers met the sea, perhaps in a brackish (mixed salt and fresh water) lagoon.

The stratigraphy of the Great Estuarine Group, and location of the Isle of Eigg.

The Fossil

The dinosaur bone is now part of the collections at National Museums Scotland (specimen number NMS G.2020.10.1). It was removed from the shoreline using rock saws, and the bone carefully extracted from the remaining rock by expert preparator, Nigel Larkin. The Eigg bone is half a metre long, and each end is missing, which makes it hard to identify what it is. There are tooth marks on the surface, which tells us it was scavenged after death. Nigel used a kind of glue to reinforce the bone and prevent it from breaking further. There was a section of the bone missing in the middle, so Nigel used the indent in the rock as a cast, reconstructing this missing part. 

The Eigg bone, NMS G.2020.10.1. A) the bone within the rock, partly excavated, and B-C) the bone reconstructed and removed from the rock.

Matthew Humpage photographed the fossil so that we could use the pictures for the paper, then he made a photogrammetry model of the bone, which is online and free to access on a site called Sketchfab. The fossil was also studied by thin-section, allowing us to look at the internal structure. This was done by Gregory Funston, who cut a thin slice through the bone in cross-section. He ground and polished this slice down to make it thin enough to pass light through, then examined it with a microscope. We used the information about the bone structure, along with comparisons with dinosaur bones from across the UK and rest of the world, to work out what kind of animal it belonged to.

Bite marks in the Eigg Dino Bone.

Identity of the Eigg Dinosaur

Our team had to work together to figure out what animal the Eigg bone belonged to, and which bone it could be. Because there have been many marine reptile fossils found on Eigg, marine reptile expert Davide Foffa compared it to these extinct ocean-going creatures. Swimming animals have special adaptations in their bones for their way of life, including having very short, wide limb bones, and thickened internal bone structure. Not only was the Eigg bone not the same shape as a marine reptile bone - it was too long and slender – it was not thickened like a marine animal bone. This meant we could be sure it wasn’t a marine reptile, and must be some kind of dinosaur.

Next we compared the bone to the three main groups of dinosaurs: theropods, sauropods, and ornithiscians. Co-authors Stephen Brusatte, Femke Holwerda, and Susannah Maidment are all dinosaur experts, and so were able to work systematically through all the possible identifications, narrowing it down. Because it was badly damaged, the Eigg bone didn’t have any diagnostic features (features that help identify the species) to guide us. Instead, we had to use detective work to narrow down the possibilities. It didn’t match the shape of theropod bones, but bore some resemblance to sauropod fibulae – the smaller of the two lower hind leg bones. It was also similar to a sauropod femur, but it would have to have been a particularly small, slender sauropod. Overall, the Eigg bone bore the closest resemblance to an ornithiscian fibulae, having the same length and width, and similar shape in cross-section. Ornithiscians include Stegosaurus and other armoured dinosaurs, which are already known from the Jurassic of the Northern Hemisphere, including sites in England.

Top) the skeleton of a Stegosaurus (from Natural History Museum London) showing the lower hind leg bones. Bottom) the cross-section of the Eigg Dino Bone, used to study the microscopic structure.

Greg’s cross section of the bone gave us the final clues we needed to identify it. He could tell from the fine detail of the bone structure that it was most likely an ornithischian – specifically a thyreophoran, which includes animals like Stegosaurus. The holes left behind by blood vessels told us that it had a relatively slow growth rate – unlike sauropods which grow very quickly to large sizes. There was a lot of secondary remodelling in the bone, which is when the bone alters as the animal grows. Very similar patterns are seen in stegosaurs like Hesperosaurus, Kentrosaurus and Stegosaurus.

Another thing Greg could see in the bone structure were lines that accumulate as the animal matures. These are known as LAGs (lines of arrested growth), and are found not only in bones, but also in teeth. The Eigg bone had a single LAG, which tells us it was older than one year in age, perhaps just a few years older – a youngster by dino standards. There was no sign that growth had stopped, so it was probably still actively growing before it died.

Conclusions

Putting all of this information together, we can tell that this is a limb bone from a stegosaur-like dinosaur. It is most likely a fibula, or hind lower leg bone. The animal was only young when it died, and was washed into a lagoon by the sea, or perhaps just off-shore, where it was chewed-on by marine reptiles.

Although dinosaur fossils in Scotland are few, and much less complete than those found in more famous Jurassic exposures in England, they are equally important. They add data to our Spartan picture of this time period. The bone from Eigg is also significant for Scotland as the first dinosaur fossil outside of Skye, and the first belonging to a stegosaur-like, thyreophoran dinosaur. It backs up the suggestion made recently by Paige dePolo and her co-authors that fossil trackways found on Skye belonged to thyreophorans.

It has taken 200 years of searching to find this dinosaur fossil on Eigg, but hopefully it won’t take as long to find the next one! Our team is grateful to our sponsors and the people of Eigg for their support – hopefully there are many more fossil discoveries to be made in the Inner Hebrides to enrich our understanding of life in the time of dinosaurs.

On Finding a Dinosaur

They tell me I’m good at finding things. Word searches, jigsaw puzzles - they are unintentional brain-training to isolate patterns in chaos. When looking for fossils it takes a few attempts to recognise what you’re seeking. Then they say you ‘get your eye in’, or that you ‘have the eye’ for it. I tell them, I have two.

I found my first dinosaur on a glorious sunny day in the Inner Hebrides. I leapt from boulder to boulder across the foreshore of the Isle of Eigg, sprinting like a mountain goat back to my teammates. With each jump I looked down to place my feet securely on dry Jurassic sandstone, which Velcro-gripped the soles of my tattered hiking boots. The stench of sulphur was making me dizzy – a nearby pool choked in marine algae was festering in the hot May sunshine. To avoid it, I moved up shore. As I flew down from a high platform into a small shingle inlet, I saw a silhouette. Long, with a bulbous end. Pattern recognition. 

Shoreline on Isle of Eigg, with Isle of Rum in the distance.

Momentum carried me several steps further along the clattering shingle before I fully registered what I’d seen. I skidded and turned back. The shape was nestled in a boulder tucked below the sandstone outcrops. I crouched down and reached out, running my fingertips across the rough surface. The electric-thrill formed a Bifröst to the ancient past.

Most fossils are not worth collecting, and that’s where scientific knowledge comes in. It was my fourth palaeontological expedition with teams working in my home-country of Scotland. That day in 2017 I recognised the black splodge on the rocks of the foreshore as the remains of a limb bone. It looked like burnt charcoal, the surface cracked as though oven-baked. Where the bone was damaged I saw the tell-tale honeycomb of a structure once-living; the strut of biological architecture, nature’s engineering exposed. A portion of the long mid-shaft was gone, leaving a ghostly indent in the rock. A million frozen grains of sand encased one end of the bone, reluctant to let it go. This stone had carried it for 166 million years like a time-capsule. It was a dinosaur limb bone. I took photographs, then turned and sped South again. 

The Eigg dinosaur bone, or StEiggosaurus, moments after I found it.

When I found my team mates I told them I’d found something. What is it? they asked. I knew how disappointing it was when your ‘fossil’ find turned out to be a bit of driftwood, or a splatter of solidified tar, so I replied that I wasn’t sure, but maybe a limb bone... What kind of limb bone? They pressed. I sheepishly mentioned some possibilities, non-commitally mumbling dinosaur.

I led them back along the shore. When they caught up and saw it, their faces exploded like grin-grenades. They knelt and examined it, agreeing it was indeed a dinosaur limb bone. The first dinosaur I’d found, and the first dinosaur ever found on the Isle of Eigg.

We took photographs and notes, planning how it could be collected. In the following weeks a team arrived by boat to slice through the shore and cut out its dinosaur heart. This bone - which had drifted offshore in the Jurassic sea and come to rest in a sandy bed for a geological nap - now drifted once again, southwards to the lab of our colleague, Nigel Larkin. He carefully removed the surrounding sandstone, exposing the limb bone for us to study.

My artwork showing the kind of dinosaur the Eigg bone belonged to. It may have died crossed a river or delta, and been washed out to sea.

It was scarred by scavengers, and the ceaseless surf of Eigg had made off more than half the evidence, one granule at a time. To figure out to which animal it belonged, I worked with palaeontologists who specialise in different groups of extinct reptile: Femke Holwerda (sauropod-lover), Susannah Maidment (queen of stegosaurs), Davide Foffa (marine reptile chaser), Stephen Brusatte (theropod enthuser). With so little of the bone left to study, we turned to the tell-tale biological structure for further clues. Gregory Funston examined the microscopic structure of the bone, a codex for an animal’s growth. The evidence combined to tell us that this was the leg bone of a stegosaurian dinosaur, a plate-backed herbivore of the Jurassic. An early resident of Eigg, now at rest in the National Museum of Scotland in Edinburgh.

By the time the whole team had assembled to look at the discovery on the shoreline that Summer’s day, I was already elsewhere. I’m restless as a wave, prefering movement. Hopefully life will always find me leaping along fermenting shorelines and shuffling below cliffs. I revel in zenful hours squinting at glinting surfaces, with salt spray scratching my lips and flaying my fingertips, sifting through ancient sands for fragments of Jurassic Scotland. 

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Panciroli, E., Funston, G. F., Holwerda, F., Maidment, S. C. R., Foffa, D., Larkin, N., Challands, T., dePolo, P., Goldberg, D., Humpage, M., Ross, D., Wilkinson, M., Brusatte, S. L. 2020. First dinosaur from the Isle of Eigg (Valtos Sandstone Formation, Middle Jurassic), Scotland. Earth and Environmental Science Transactions of the Royal Society of Edinburgh, 1-16.

Killing-off Scottish Mammaliamorphs

With all that’s been going on in the last couple of months (including attending #2017SVP, Friends of  Hugh Miller’s conference, and #SVPCA2017), I’ve dropped the ball on this blog a little. But this week past, I had a new paper out with my colleagues, and I’d like to tell you a little more of the story behind it.

When I started my PhD on the fossil material of the Isle of Skye, one thing really surprised me. There is this whole group of cynodonts (the group that includes mammals and their nearest relatives) that no one ever talks about. They are called tritylodontids (Tritylodontidae), and despite being one of the most successful clades of cynodont – lasting from the Late Triassic to the Early Cretaceous - they are often overlooked by palaeontologists. We find one of them, called Stereognathus, on the Isle of Skye.

Perhaps the best piece of tritylodontid palaeoart, Stereognathus by Mark Witton - find out about him and support his amazing work.

Why should we care about these extinct animals? Well, they’re considered by most to be the sister-group to stem-mammals, and share many similarities in their skeleton. They would have had fur and whiskers, and you might mistake one for a mammal if you didn’t look too closely. But there are some interesting differences. Tritylodontids kept the so-called “reptilian” jaw joint, between the articular and quadrate bones (not the dentary squamosal contact as in mammals). They also didn’t go through the same extreme reduction in body size we see in the first mammals. In fact some tritylodontids were pretty big, like Kayentatherium from the Early Jurassic, which was about a metre long. Unlike the earliest mammals, tritylodontids appear to have been almost exclusively herbivorous. 

All in all, they were occupying quite a unique ecological space in the Mesozoic. 

The first tritylodontid to be described was the Middle Jurassic genus, Stereognathus, named by Charlesworth in 1855 and figured by Richard Owen shortly after. Unfortunately though, this genus is represented by only a few molar teeth in a fragment of jaw, a bunch of isolated teeth, and some individual bits of limb that might belong to Stereognathus, but it’s uncertain. Most of this material came from sites in Oxfordshire, England.

Owen's original figures from 1857, scanned courtesy of BHL

Charlesworth called this first Stereognathus species, S. ooliticus, after the rocks they were found in, the Great Oolite Group. More than 100 years later, Robert Savage and Michael Waldman found teeth they identified as belonging to Stereognathus on the Isle of Skye. They named it S.hebridicus, after the Inner Hebrides islands, to which Skye belongs. Unfortunately, their only diagnostic feature was that S. hebridicus was bigger than S. ooliticus. More recently, field work has recovered more S. hebridicus teeth. I decided to set out with my co-authors to test this size difference, and see if we could find other details of the shape of the teeth that would support S. hebridicus as a separate, Scottish species.

A photo of the most intact Stereognathus specimen, found and photographed by Andrzej Wolniewicz during fieldwork on the Isle of Skye.

We microCT scanned all the new material, and the two holotypes of S. ooliticus and S. hebridicus. We measured every tooth of Stereognathus we could, many being too broken up or worn to give reliable measurements. Even the original S. ooliticus specimen figured by Owen was in a poor state: comparing it to his original drawings, it seems over 150 years of handling hasn’t been kind. 

We didn’t find any good evidence that S. hebridicus is a separate species from S. ooliticus. Although the holotypes are radically different in size, when you take all of the rest of the teeth we have and plot them (below), they fall along a line of size change you’d see from baby to adult. In other words, size differences are explained by ontogeny: development from earliest stage of life to maturity.

All of the measureable upper postcanines of Stereognathus. Empty diamonds and squares indicate less certain measurements (due to breakage or wear). I expect field work over the coming years will fill this out to show a full growth series of size.

To my horror, I’ve sunk the only Scottish tritylodontid! Unless new fossils tell us differently, it looks like S. hebridicus is no more. This makes it a junior synonym to S. ooliticus. It’s a shame to see our Scottish species go, but I’m glad that it was the new, more physically intact fossil material from Skye that allowed us to make a proper reassessment of the genus. 

Who knows, perhaps there is still another species of tritylodontid to be found on the rocky shores of the misty Isle? I'll keep looking and get back to you...

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Panciroli E, Walsh S, Fraser NC, Brusatte SL, and Corfe I. 2017. A reassessment of the postcanine dentition and systematics of the tritylodontid Stereognathus (Cynodontia, Triltylodontidae, Mammaliamorpha) from the Middle Jurassic of the United Kingdom. Journal of Vertebrate Paleontology.

Waldman M, and Savage RJG. 1972. The first Jurassic mammal from Scotland. Journal of the Geological Society of London.

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Elizabeth Anderson Grey - Scottish Lady Palaeontologist

Have you heard of Elizabeth Anderson Gray? She was one of the most important and prolific female Scottish fossil collectors of her time, responsible for amassing collections that are still vital to our knowledge of the stratigraphy and species composition of the Ordovician and Silurian rocks of Scotland.

Born in Alloway, Ayreshire, to an Innkeeper, Elizabeth’s family then relocated to become farmers in Girvan, a small coastal town 60 miles south of Glasgow. Although she moved occasionally in her life (to Glasgow and to Edinburgh), it was from the rocks around Girvan that Elizabeth would collect most of her specimens during her long lifetime.

Elizabeth Anderson Gray spent her entire life fossil hunting. Her collections were vital to our understanding of early life on earth. (Picture from Carrick Scotland: Beyond the Tourist Guides)

Elizabeth’s father, Thomas Anderson (who had a trilobite and a coral named after him), introduced her to geology and fossil collecting when she was a child. From this point onwards she collected assiduously, continuing until the autumn before her death, at the age of 93. Like many women collectors, Elizabeth Anderson Gray was overshadowed publically by her husband Robert Gray, co-founder of The Natural History Society of Glasgow (NHSG), under whose name much of their joint wor was presented. This was necessary in the 1800s as most Societies where their finds might be presented did not admit women until the turn of the century.

 

Elizabeth Gray was dedicated to record keeping and extending our understanding of the diversity of early Palaeozoic life. Despite her modest early education, her lifelong learning was augmented in 1869 when she was invited to attend geology lectures for women at the University of Glasgow.

Elizabeth was clearly an astute woman. She ensured the importance of her finds was recognised by having them formally described by established scientists (who were of course, all men). Her legacy also survived in the Gray Collections, which were sold to museums across the United Kingdom, the main ones being the Natural History Museum in London and the Hunterian in Glasgow. Many of her finds are type specimens, the material that defines a species taxonomically, such as Hudsonaster grayae (an early starfish), Archophiactis grayae (also an echinoderm), and Lophospira trispiralis (a type of mollusc).

One of the fossils from the Gray Collection. ©The Trustees of the Natural History Museum, London

Many specimens collected by Elizabeth are referred to in the proceedings of the Natural History Society of Glasgow between 1868 and 1878, and unlike many other women geologists of her time (notably Mary Anning) she even had the honour of having some named after her – although it was the surname she shared with her husband, rather than forename, that was mostly used for this purpose. Other material was named for Girvan, the area she found it in.

Using her detailed observational skill, Elizabeth presented a list of the fossils she collected in Ayrshire which was extensively used by other geologists in both Scotland and England. It formed an important contribution to the British Geological Survey’s volume on Silurian Scottish rocks.

The Grays were friends with the well-known geologist Charles Lapworth and fossil collector Jane Donald Longstaff.  Although considered by both herself and the professionals of the day as an amateur, Elizabeth was undeniably a skilled one; responsible for uncovering a great deal of the diversity of Palaeozoic rocks in Scotland. Years of collecting led Elizabeth to be well versed in geology and sedimentology, keeping careful records of her work. It is because she recorded the locations, geology and associations of each of her specimens that Gray’s collections remain invaluable to those studying the Ordivician and Silurian today. 

After her husband’s death in 1887, Elizabeth continued to collect fossils, often with the help of her two daughters, Alice and Edith, who undoubtedly knew a great deal thanks to the many “geologising” family holidays taken over the years. In 1900 Elizabeth’s contributions to geology were recognised by the Geological Society of Glasgow, who made her an honorary member. The Natural History Society of Glasgow followed suit a year later.

In 1903, at the stately age of 72, Elizabeth was awarded the Murchison Geological Fund from the Geological Society of London, for her lifelong contribution to early Palaeozoic geological research. She continued to collect and disseminate her material until the year before her death from bronchitis on 11th February, 1924. 

Elizabeth's daughters continued her work, they were known as "the Misses Grey". ©The Trustees of the Natural History Museum, London

She had spent almost a century working in the field, and yet so few people know her name. Her daughters – referred to as “the Misses Gray” - continued to collect; diligently uncovering new specimens as their mother had before them. They eventually sold her remaining collection to the Natural History Museum, ensuring their mother’s work would survive and remain available for future scientific study. 

Without her, our understanding of the early Palaeozoic in Scotland and the UK would be much the poorer.

(this article first appeared on Trowelblazers.com 27/5/15)

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To find out more about the Gray collection at the Natural History Museum in London, search for her fossils here: http://data.nhm.ac.uk/

For more on the geology of Girvan, and the rest of Scotland, try http://www.scottishgeology.com/geo/regional-geology/southern-uplands/girvan-to-ballantrae-coast/

References

Burek, C. V., & Higgs, B. (2007) The Role of Women in the History of Geology. The Geological Society; Bath.

MacBride E. W., & Spencer W. K (1938) Two New Echinoidea, Aulechinus and Ectinechinus, and an Adult Plated Holothurian, Eothuria, from the Upper Ordovician of Girvan, Scotland. Philosophical Transactions of the Royal Society of London, Vol. 229

McCance M. (2002) Hugh Miller, 1802-1856, Geologist and Writer: His Links with 19th Century Girvan. Ayrshire Notes No.23

Peach, B. N, Horne, J., & Teall, J. J. H. (1899) The Silurian rocks of Britain: Vol. I.Scotland. Glasgow: J. Hedderwick & Sons. Available from: https://archive.org/details/silurianrocksbr00tealgoog

 

Weddel, R.  ‘Some Significant Women in the Early Years of the Natural History Society of Glasgow’ [online]. Available from: http://www.glasgownaturalhistory.org.uk/gn25_3/weddle_women.pdf