About 200 dinosaur footprints dating back 166 million years were uncovered across the limestone floor of Dewars Farm Quarry in Oxfordshire, forming the largest known trackway site in the United Kingdom. The marks are attributed to long-necked sauropods, probably Cetiosaurus, and the carnivorous Megalosaurus.
The longest exposed trackways extend 150 metres, although researchers believe they may continue beyond the excavated area. Quarry worker Gary Johnson first noticed regularly spaced ridges while removing clay with a digger. Because another footprint site had been discovered nearby during the 1990s, the repeated features led him to suspect a dinosaur trail.
The ensuing excavation involved a group exceeding 100 volunteers, students and scientists. Four trackways came from plant-eating sauropods that moved on four legs. Their rounded prints resemble much larger versions of elephant footprints, consistent with animals that could reach 18 metres in length.
A fifth trail was attributed to Megalosaurus. Its three distinct toes form what palaeontologists call a tridactyl print. Dr Emma Nicholls of the Oxford University Museum of Natural History said these two-legged predators were agile hunters measuring about six to nine metres and were the largest known predatory dinosaurs in Jurassic Britain.
At the time the animals crossed the area, a warm, shallow lagoon covered the landscape. They pressed their feet into mud that was later preserved. Professor Richard Butler of the University of Birmingham said a storm may have rapidly deposited sediment over the tracks, protecting them from being washed away, although the precise preservation event remains unknown.
The team made casts and took more than 20,000 photographs. Those images were used to build three-dimensional models of individual footprints and the whole exposed site. Unlike bones alone, a sequence of prints can show how an animal moved and provide direct evidence about the surface and environment it crossed.
One section records the paths of a sauropod and Megalosaurus intersecting. Researchers believe the sauropod passed first because the leading edge of its large round print was compressed by the later three-toed footprint. The overlap allowed scientists to reconstruct the order of two animals' movements across the same ground.
The future of the tracks had not been decided. Researchers were working with quarry operator Smiths Bletchington and Natural England on ways to preserve the site. Because excavation covered only part of the quarry, more footprints may remain beneath surrounding material. The combination of scale, long trails and intersecting tracks makes the discovery a record of repeated animal movement rather than a collection of isolated impressions. Only part of the quarry had been excavated.
