Gary Johnson was clearing clay with a digger at the Oxfordshire quarry where he works when he hit an unexpected bump in the limestone surface.

“I thought, it’s just an abnormality in the ground,” he said. “But then it got to another, three metres along, and it was hump again, and then it went another three metres, hump again.”

What Johnson had discovered was part of an enormous dinosaur trackway dating to nearly 166m years ago, when the quarry was a warm, shallow lagoon crisscrossed by the huge creatures.

“I thought I’m the first person to see them,” Johnson, a worker at Dewars Farm Quarry, told the BBC. “And it was so surreal – a bit of a tingling moment, really.”

Researchers have now unearthed about 200 large footprints at the site, making this the biggest dinosaur trackway ever found in Britain. The tracks are thought to have been made by two types of dinosaur: the herbivorous cetiosaurus, a sauropod that walked on four legs, and the smaller carnivorous megalosaurus.

So far, five separate trackways have been found stretching up to 150 metres in length, and experts from the universities of Oxford and Birmingham believe they could extend much further as only part of the quarry has been excavated.

“This is one of the most impressive track sites I’ve ever seen, in terms of scale, in terms of size of the tracks,” Prof Kirsty Edgar, a micropalaeontologist from the University of Birmingham, told the BBC. “You can step back in time and get an idea of what it would have been like, these massive creatures just roaming around, going about their own business.”

View image in fullscreen

After Johnson’s initial discovery, a team of more than 100 scientists, students and volunteers joined an excavation of the site last summer, which will feature on the BBC series Digging for Britain next week. As well as making plaster casts of the prints, the project recorded 20,000 photographs and built detailed 3D models of the site using aerial drones.

The trackways connect to discoveries made in the area in 1997, where limestone quarrying revealed more than 40 sets of footprints. One area of the site even reveals where the paths of a cetiosaurus and megalosaurus crossed, with the sauropod having got there first. The front edge of its large, round footprint is slightly squashed down by the three-toed megalosaurus walking on top of it.

Dr Duncan Murdock from the University of Oxford said: “Knowing that this one individual dinosaur walked across this surface and left exactly that print is so exhilarating. You can sort of imagine it making its way through, pulling its legs out of the mud as it was going.”

The megalosaurus print is “almost like a caricature of a dinosaur footprint”, Dr Emma Nicholls, a vertebrate palaeontologist from the University of Oxford Museum of Natural History, told the BBC. “It’s what we call a tridactyl print. It’s got these three toes that are very, very clear in the print.”

The creatures were agile hunters, she said. “The whole animal would have been 6 to 9 metres in length. They were the largest predatory dinosaurs that we know of in the Jurassic period in Britain.”

View image in fullscreen

Prof Richard Butler, a palaeobiologist at the University of Birmingham, said dinosaur footprints provided a snapshot of the life of the animal. “The really lovely thing about a dinosaur footprint, particularly if you have a trackway, is that it is a snapshot in the life of the animal,” he said.

“You can learn things about how that animal moved. You can learn exactly what the environment that it was living in was like. So tracks give us a whole different set of information that you can’t get from the bone fossil record.”

Why these particular trackways were preserved remains unknown. “Something must have happened to preserve these in the fossil record,” Butler said. “We don’t know exactly what, but it might be that there was a storm event that came in, deposited a load of sediments on top of the footprints, and meant that they were preserved rather than just being washed away.”

• Dinosaurs
• Palaeontology
• Oxfordshire
• England
• Research
• Fossils
• Evolution
• news