Mission Jurassic:

Where dinosaurs once walked

It's been 145 million years since the last Jurassic dinosaurs roamed the planet. 

Millennia have passed and today on the prairies of northern Wyoming, USA, it is hot and arid. At a glance, away from the isolated towns, the landscape is devoid of much save juniper, sagebrush and the occasional rattlesnake or black widow spider.

But evidence of a prehistoric world filled with lush greenery, dinosaurs and a variety of other extinct animals are just below the rocky surface.

In summer 2019, scientists from the Natural History Museum, London, set out for Wyoming to help reveal what has been hidden for millions of years.

The Morrison and Sundance formations

From approximately 160-157 million years ago, a shallow sea known as the Sundance Sea covered much of western North America. It was connected to the ocean by a narrow channel that stretched north for over a thousand miles.

As this sea withdrew, it was replaced by rivers and floodplains which deposited sediments and formed the rocks known as the Morrison Formation. Today only a small amount of this approximately 1.5-million-square-kilometre formation is accessible for palaeontologists to explore.

Dr Maidment says, 'During the Late Jurassic Period, about 150 million years ago, this area of Wyoming was a broad, shallow plain inhabited by dinosaurs like Stegosaurus, Diplodocus and Allosaurus. There were forests and plants - it would have been quite a green landscape.'

On the Jurassic Mile, evidence of these prehistoric reptiles is scattered across the landscape, with fossilised bones naturally weathering out of rocks and tumbling down the hillsides almost everywhere you look, and even more being slowly dug out of two quarries.

As well as the dinosaur-bearing Morrison Formation rocks, a large swathe of rocks laid down by the earlier sea are also exposed.

Some of the rocks of the Sundance Formation were deposited within a calm lagoon in exceptionally thin layers called paper shales. Palaeontologists can gently tease the layered rocks apart by hand or with tools to find plants and ancient animals, such as small fish and insects, fossilised between them.

Fossil fish curator Emma Bernard says, 'The rock is very finely laminated. It's almost like the pages of a book.

'A lot of the fish we found are quite small compared to the dinosaur material we see in the Morrison Formation, and they are very fragile. So we had to be really careful when we were excavating.'

The team also found abundances of belemnites, Gryphaea and oysters at different layers within the Sundance Formation, providing evidence of different marine environments.

Fossil invertebrates curator Dr Tim Ewin explains, 'Oysters are strange animals that can live in parts of the sea that other animals find difficult, whether because of the salinity, temperature or even the roughness of the water. As they are one of the few organisms capable of tolerating extreme environments and grow quite quickly, oysters can dominate an area. You can end up with very thick beds of oysters.

'If you see a profusion of oysters, it tells you that there is something unusual about the environment.'

The accumulations of different fossils found throughout the Sundance Formation, on the Jurassic Mile and elsewhere, provide evidence that sea levels and conditions changed considerably over time.

Tools of the trade

The Jurassic Mile has been explored by the Children's Museum in previous years. When Prof Barrett and his crew arrived in Wyoming in 2019, their first job was to begin clearing the site, which had spent the winter buried under a protective layer of rocks. 

Prof Barrett says, 'We got into the quarries and started shifting rock and sweeping down the surfaces so that we could see what was going on.'

Once they had reached the bone bed, they slowed down and began to painstakingly reveal ancient animals millimetre by millimetre - a job Dr Maidment and her crew continued when they arrived on site two weeks later.

Mark Graham is the Natural History Museum's senior fossil preparator. His day-to-day role involves working with the fossils that palaeontologists bring back from expeditions. But on Mission Jurassic, he got to dig up the bones himself.

He says, 'It was fantastic on the first day to uncover a scapula of one of these gigantic dinosaurs, and later to find a large claw bone.

'Normally when I'm at the Museum, I'm used to opening field jackets, taking fossils out and making sure they're repaired if necessary. So exposing and stabilising them in the quarry is a slight role reversal for me.'

Finding large dinosaur bones isn't easy, but it's nothing compared to uncovering those of smaller animals, such as amphibians and mammals, which lived alongside them.

Finding microvertebrates is an important part of understanding what the environment would have been like in a particular area millions of years ago. A vertebrate is anything with a backbone. Microvertebrates are the parts of vertebrate animals, such as teeth or small bones, that have to be identified using a microscope.

It can be difficult to tell whether you're looking at a habitat the dinosaurs lived in, such as a coastal plain or forest, or where carcasses were washed to after death. But by finding other fossils around the dinosaur bones, you might get a better idea.

This is where Dr David Ward comes in.

He says, 'My initial interest is the evolution of sharks, but in order to collect sharks, I have to do a lot of sieving. So I developed an automated sieving machine that gently removes whatever is in the sediment without causing damage.'

Led by Dr Ward, the Mission Jurassic team constructed Hank, a field-based machine to speed up the microvertebrate sieving process.

Hank mimics the natural weathering process. It creates an artificial rainstorm with lawn sprinklers that spray water onto sediment samples to wash away clay and reveal tiny fossils.

A new experience

An opportunity to experience a real dinosaur dig is rare. For many, getting involved would be a dream come true.

Lead scientist Prof Phil Manning of the University of Manchester and the Children's Museum of Indianapolis says, 'I would have sawn off limbs to have this kind of experience as a student.'

Of the few students invited to join the dig, he says, 'I think it will have immeasurable positive outcomes in their careers, having taken part in an excavation like this.'

For three of the Natural History Museum's PhD students - Joe Bonsor, João Leite and Tom Raven - Mission Jurassic was their first experience of palaeontological fieldwork and, for some, the dig couldn't have started any better.

'I found a bone on my first day. We think it was a small piece of rib or part of a backbone,' explains Bonsor.

'Finding my first dinosaur bone was one of my main goals going out on the dig, and it was incredible. I was able to excavate the whole thing, wrap it in plaster and package it up safely.'

Leite says, 'It was a really cool experience and I tried to learn as much as I could. I was digging, prospecting and jacketing bones - all the sorts of things you can imagine happen on a dinosaur dig.

'I think one of the best bits was jacketing - just getting your hands covered in plaster, and protecting the bones and the surrounding rocks so they can be safely transported.'

The PhD students have each taken part in non-palaeontological fieldwork previously, but Mission Jurassic offered up some brand-new experiences.

'A big part of Mission Jurassic for me was to learn field techniques and become a bona fide palaeontologist,' explains Raven.

'It was definitely the largest expedition I've been part of. We had three international groups joining together with people with different expertise and specialities. Having that kind of collaboration is really great.

'I've never been involved in anything quite like it before. I had no idea what to expect.'

International collaboration

Mission Jurassic is led by The Children's Museum of Indianapolis in partnership with The Natural History Museum, the University of Manchester and Naturalis Biodiversity Center.

The Children's Museum intends to dig out two sauropod dinosaurs from the Jurassic Mile for display in Indianapolis, but has also been working alongside other institutions with a variety of expertise to study what the Jurassic environment and its dinosaurs were like.

Dr Maidment says, 'The Jurassic Mile is one piece of a jigsaw puzzle that is going to help us understand what environments the dinosaurs were living in across western North America.'

'This is a very unusual excavation insofar that we're dealing with a big international team,' explains Prof Manning.

'One of the most amazing things about science is when you get teams working together you can often discover things that you can't as individuals. My hope for the end of this project is that we've had multiple teams working together, pushing back the boundaries of science, helping us understand areas that we've never thought to look to before.'