Kilt Rocks of north east Trotternish, on far right

Kilt Rocks of north east Trotternish, on far right

For most, it is a place that makes the heart soar. To the north, water from a nearby loch tumbles 60 metres into the sea with the towering red basalt columns of the Kilt Rocks in the background. Across the Sound of Raasay, the snow-capped giants of Torridon reach up to touch the clouds.

Despite these natural gems, my heart is sinking. I’ve come to the shoreline on the eastern coast of the UK's Isle of Skye, on a promise of seeing a sea monster. The flight to Inverness in Scotland, late-night drive and early start would all be worth it to witness the dramatic extraction of a giant fossilised ancient marine reptile from a large boulder. Except having journeyed here, it turns out the beast and the boulder that holds it captive are underwater thanks to an unusually high tide.

If Steve Brusatte, from the University of Edinburgh, and his team are as disappointed as I am, they’re hiding it well. Hopping from rock to rock like children on an Easter egg hunt, they debate whether various dark patches are bone or wood. Local amateur palaeontologist Dugald “Dougie” Ross attacks a boulder containing a matchbox-sized black blob with a rock saw, and, after a long, loud and dusty race against the tide, he emerges triumphantly with what may be part of a dinosaur bone. This seems, to me at least, a poor consolation prize.

Steve Brusatte and Tom Challands inspecting a fossil tooth

Steve Brusatte and Tom Challands inspecting a fossil tooth

Brusatte however has a gleam in his eye and a bounce in his step. The previous day, he confides, they made a big discovery. They’ve found some footprints, dozens of them, he says quietly. Huge ones belonging to giant, long-tailed, plant-eating sauropods. It’s early days, he emphasises, but it could be a world-class find that changes our understanding of how some of the biggest animals ever seen on Earth lived their lives.

Vertebrate life in the Middle Jurassic - from around 174 to 164 million years ago - is poorly studied because of a relative lack of available fossils, yet it was a geological epoch of critical importance as a time of major transformations. Recent examination of remains found on Skye has led Brusatte and others to re-evaluate current thinking about the evolution of large marine reptiles called ichthyosaurs, which ruled beneath the waves at the time. They’re in the process of studying newly discovered shark and other fish teeth, and fossilised small reptile bones. Together, this material, along with previously unearthed remains from early mammals and amphibians, is helping scientists find many new pieces in the jigsaw of the history of life.

Ichthyosaur jaw and associated teeth impressions from Skye

Ichthyosaur jaw and associated teeth impressions from Skye

At least 50% of life on Earth was wiped out in a mysterious extinction event between the Triassic and Jurassic

At least 50% of life on Earth was wiped out in a mysterious extinction event between the Triassic and Jurassic

Around 200 million years ago, something triggered most terrestrial and marine species to become extinct. The cause of the mass extinction event, which marks the start of the Jurassic geological period, is still a matter of debate. What is clear however is that it opened the ecological doors that allowed dinosaurs to dominate on land for the next 136 million years or so.

A period of especially accelerated change occurred during the Middle Jurassic as the supercontinent Pangaea began to break apart into the continents we know today. Dry, desert-like inland zones gave way to large flooded areas, temperate regions and tropical forests. Animals, plants and other living organisms either died out or adapted to their environment. Early mammalian ancestors of humans underwent especially rapid evolution. Many important dinosaur groups such as the tyrannosaurs and plate-backed stegosaurs made their first appearances, the first birds probably took wing, and new large reptiles were taking over and spreading in the oceans.

“The Middle Jurassic was a really interesting period in the history of life, when there was a whole lot of evolution going on,” says Brusatte. “What is really frustrating is that we have a lot of fossils from different places with fossils from the Early Jurassic and the Late Jurassic, but there is relatively little fossil-bearing Middle Jurassic rock around.”

Skye is one of the few places in the world that has fossil-bearing rocks from the period, meaning new discoveries made here have the potential to answer some of the major questions scientists have about how lifeforms evolved the way they did. It also explains why Brusatte, Ross, their colleagues and a two-man BBC Earth team are gathered on the beach below Valtos, poking about in the rocks and sawing chunks out of them on a brisk morning.

Cast of 1982 ornithopod footprint in the Staffin Museum, Skye

Cast of 1982 ornithopod footprint in the Staffin Museum, Skye

The first evidence of dinosaurs found in Scotland came in 1982 with the discovery on Skye of a 47cm-long footprint believed to have been made by a plant-eating, Iguanodon-like ornithopod. Fossilised parts of bones from sauropods, theropods (the mostly flesh-eating bipedal group which later included Tyrannosaurus rex) and an armoured thyreophoran (the group that includes stegosaurs and ankylosaurs) have since been found on the island. In 2002, a footprint made by a small ornithopod was discovered by local woman Cathie Booth as she walked her dog at An Corran, Staffin Bay, a little to the north of Valtos. Further searches revealed 15 more, up to 53cm-long. These were particularly significant because they are still in their original rock strata, whereas previous footprints found on Skye were in loose boulders, making it harder to work out where they fit into the wider geological picture. Neil Clark of the Hunterian Museum in Glasgow, Scotland, who studied them, suggested they could be from a large meat-eating predatory dinosaur similar to Megalosaurus.

Many of the most important finds on Skye have been made by Ross, a Gaelic-speaking native and builder who has been collecting fossils on the island for almost four decades to display in the Staffin Museum, which he set up in Ellishadder as a 19-year-old in 1976. In 2002, for example, on a remote beach in the north of the island, he found a slab of sandstone showing the footprints of an adult theropod along with those of 10 smaller individuals - rare evidence suggesting post-hatching parental care by a dinosaur.

Brusatte, Ross and others involved in the most recent expedition are members of PalAlba, a network of palaeontologists set up in 2013 to better coordinate the tracking down and study of Scottish vertebrate fossils through collaboration. The first fruits of the consortium’s labours came earlier this year with the discovery of a new species and genus of ichthyosaur - the family of large predatory reptiles that were among the top predators beneath the waves at the time dinosaurs ruled on land. In January, Brusatte and colleagues announced the discovery of Dearcmhara shawcrossi, named after amateur collector Brian Shawcross who found the fossilised humerus and vertebrae at Bearreraig bay on Skye in 1959.

The creature, which resembled a cross between a dolphin and a crocodile, was around four metres long. It was only recently identified as a new species following a recent examination of the remains kept at the Hunterian Museum.

After the Middle Jurassic, larger, more advanced ichthyosaurs became dominant around the world.

Dearcmhara is pronounced "jark-vara"

Dearcmhara is pronounced "jark-vara"

Brusatte and colleagues say the discovery of D. shawcrossi changes our understanding of the way these marine predators evolved, with the takeover by bigger, more developed ichthyosaurs taking place more gradually than previously thought, and occurring later in parts of Europe than elsewhere.

Duntulm Castle, Skye

Duntulm Castle, Skye

The unexpectedly high tide may have temporarily frustrated Brusatte’s efforts to track down more ichthyosaur fossils to throw more light on these relatively poorly understood predatory marine reptiles, but the team’s discovery of large numbers of footprints more than made up for the disappointment.

They were fossil hunting in the bay just south of the Duntulm Castle ruin close to the northern tip of Skye and were about to call it a day when Brusatte and his colleague Tom Challands came across some large lumps of rock sticking up from the rocky foreshore. With the sun dipping and casting long shadows, protrusions off to one side of one of them looked very much like claws and digits. Dinosaur footprints can sometimes occur in positive relief if sediment falls into the original impression and surrounding material is eroded away.
The pair then examined some nearby depressions in the rock and realised they were negative relief footprint impressions. Further inspection revealed these occurred as multiple consecutive footprints, or trackways, on different rock layers. Challands describes the moment as “an epiphany”.

The size of the footprints - up to 70cms across - their shape, and their distribution, means they could only have been left by plant-eating sauropods. There are only a handful of other known Middle Jurassic sauropod trackways in the world, including major sites in England, Portugal, Mexico, Morocco and the US.

While fossilised dinosaur bones might look more impressive, footprints can often be more useful to palaeontologists, especially “in situ” ones that are discovered where they were left, rather than in rocks that have been detached from their original site. They can help reveal what environments the animals lived in, what they ate, how they interacted with each other, their size and weight and potentially how they changed over time.

Brusatte and Challands say they appear to have been made by primitive sauropods with narrow gauge locomotion, large thumb claws and feet with straight digits. They stress that more work will be needed to be sure of the identities of the dinosaurs that made them, but they most resemble those in the Breviparopus and Parabrontopodus groups.

It was originally believed that sauropods were too heavy to live on land and needed to spend a lot of time in swamps to support their huge bulk. However, this view went out of favour in the 1960s and 1970s when new evidence on posture and growth led scientists to believe they could have happily spent most of their lives on land.

However, their discovery in what was a marine lagoon and other recent sauropod footprint finds have led Brusatte’s group to suggest it may be time for another rethink. In a paper published in the Scottish Journal of Geology, they say: “The Skye site presents a confluence of evidence for sauropods living in the region of a submerged lagoon over multiple generations.” They add that lagoons could have provided more abundant food supplies, helped them cool their bodies or possibly provided protection from predators.

Springtime in Skye, 170 mya

Springtime in Skye, 170 mya

While big beasts such as dinosaurs and sea reptiles tend to hog the headlines, Brusatte and his colleagues are often just as excited to find the remains of smaller animals, including amphibians, early mammals and fish. While on the same Duntulm Castle site where they found the sauropod footprints, members of the group exchanged high fives after postdoctoral student Hong-yu Yi found the jaw bones of what they think is a previously undiscovered species of reptile. Because smaller bones are more fragile and less likely to be preserved as fossils, they are rarer. They tend to only be found in relatively quiet environments such as lagoons, where they are protected from waves, currents and strong winds.

“Dinosaurs are important,” says Challands. “But so are the smaller things. We were very pleased to find some shark teeth on Skye. Finding and studying them can be a long process but they can tell us a lot about the diversity of the food web. There’s hardly anywhere else in the world that preserves such fossils from this period.”

Shark tooth from Skye

Shark tooth from Skye

Sometimes failure to find what we think we’re looking for can lead to more important discoveries.

Brusatte’s team didn’t manage to extract the fossilised ichthyosaur remains they were after, but came away with a more important prize. The sauropod footprints, along with their other finds, will help scientists answer some of the major outstanding questions about how dinosaurs lived and evolved during the Middle Jurassic.

Whether or not they lead to a reinterpretation of how sauropods lived will depend on more detailed analysis and scientific scrutiny by others. What seems clearer however is that Duntulm Castle is set to become an internationally important site that will attract scientists and visitors for many years to come.