Eigg's stegosaur

Running across the shore of the Hebridean island of Eigg, Dr Elsa Panciroli’s eye was caught by something unusual buried in a boulder she had stepped on.

Elsa, a Research Associate at National Museums Scotland, was part of a team carrying out fieldwork in the area and had been looking for the fossilised remains of early mammals. But what she spotted in the rock wasn’t the sort of animal she had been expecting to find. Instead, she had stumbled across the first dinosaur bone ever to be discovered on the island and the first one in Scotland to be found outside Skye.

Elsa kneeling next to her find.

Elsa hadn’t expected it at all. It looked like a dinosaur bone, but she thought it couldn’t be. She remembers going back to the rest of the crew and trying not to use the D word. When the team went to check it out, everyone felt the same: it had to be a dinosaur, it couldn’t be anything else.

The Isle of Eigg is in the Inner Hebrides off the West coast of Scotland.

Skye has become a magnet for dinosaur hunters because it is one of the few places where rocks from the Middle Jurassic period can be found. These rocks contain the fossils of vertebrates (animals with backbones). Eigg has similar geology to Skye, but despite attracting fossil hunters for 200 years (including the famous 19th-century palaeontologist Hugh Miller), no dinosaurs had previously been found there.

The landscape the Eigg dinosaur once roamed would have looked very different to the island we see today and would have been warmed by a humid and Mediterranean-style climate. At that time, the Inner Hebrides were flat with river deltas and lagoons and were sometimes submerged by rising sea levels.

An artist's impression of stegosaurs on Eigg by Elsa Panciroli.

The team working there with Elsa had hoped to find marine reptiles, invertebrates and fish. Elsa studies early mammals so that’s what she’d been hoping to find. These tend to be tiny, requiring Elsa to crawl around on her hands and knees with a hand lens looking closely at the rock. It’s unusual for her to find something so big.

The bone was carefully removed from the rock and sent to Nigel Larkin in Shropshire to be prepared. Missing fragments of the bone – lost to erosion by the sea – had left indentations in the rock that were used as a cast to help recreate them.

The removed fossilised bone.

Thin-sections were made to examine the structure of the bone and comparisons made to other specimens to uncover more information about the find. It’s believed to be part of the hind leg of a stegosaurian dinosaur from 166 million years ago. This is the first fossil bone evidence that stegosaurs were living in Scotland at that time (Skye trackways reported earlier are likely to have belonged to stegosaurs).

Analysis of features such as the bone’s structure and layers of bone growth not only helped identify what type of animal it was, but also that it was only one or two years old. It’s thought the stegosaur died on the shoreline or by a river and was then washed out to sea. Small bite marks spotted on one part of the bone suggest another animal had gnawed on it after its death.

The stegosaur bone has now been added to our collections and a 3D model of it has been created. We hope to be able to display the fossil at some point, but the model is online now so everybody in Scotland and beyond can take a look. You can turn it upside down and even see the bite marks on it.

While we know it can’t be Stegosaurus itself (because it’s not quite the right time period), it’s very likely to be a close relative. As the first dinosaur discovered outside Skye, this find is significant for Scotland.

It’s also the first from this group of dinosaurs. Bones from theropods (meat-eating dinosaurs) and the big herbivores have been found before, but we’ve never found one of these. And speaking globally, fossils from land animals in the Middle Jurassic period are really rare.

Despite her ground-breaking find, dinosaurs won’t be what Elsa will be looking for the next time she returns to the island. She would like to find out about all of the different animals that lived at the same time as this dinosaur.

The ecosystems that existed on Eigg and Skye are very important for understanding how the ecosystems of today came to be. At this time in the Middle Jurassic, early representatives of animals like mammals, lizards and birds that dominate today’s ecosystems across the world were evolving. The fossils of those animals that lived in the shadow of the dinosaurs are a rare window on a vanished world that would eventually lead to ours.