Dinosaur tracks: Prehistoric chase scene reconstructed

Scientists have digitally reconstructed the scene of a dinosaur chase - preserved in the mud of an ancient river bed in Texas.

The tracks were left by two dinosaurs more than 110 million years ago.

Seventy years ago, the whole trackway was removed from the river bed and divided into blocks, which were moved to different locations for study.

Some of these blocks have been lost, but the team managed to use old photographs to reconstruct the site.

The research is published in the journal Plos One.

Lead researcher Peter Falkingham, from the Royal Veterinary College, said he and his colleagues had used just 17 photographs taken by American palaeontologist Roland T Bird, who first excavated the site in 1940.

The tracks are from two dinosaurs, a large, herbivorous sauropod, and a carnivorous theropod - the group of top predators to which Tyrannosaurus rex belonged.

"In some places the theropod tracks are in the sauropod tracks," said Dr Falkingham.

"[This means] the theropod came after. So Bird interpreted this as a theropod chasing a sauropod."

Bird also drew maps of the whole site in the Paluxy River in Texas. But since then, some of the blocks the trackway was divided into have been lost.

This study allowed the entire 45m (147ft) "chase scene" to be seen as a whole once again for the first time since it was removed from the site.

'Irrevocably lost'

Only 17 photographs were used for the reconstruction

The team used a technique known as photogrammetry - scanning and combining the photographs to build a digital model of the site.

"We now have the whole trackway in context in a single piece," said Dr Falkingham.

The method, he said, was already commonly used to make such models. But this advance took the technique a step further, in a way that could prove very useful to palaeontologists.

Dr Falkingham said: "Here we're showing that you can do this to lost or damaged specimens or even entire sites if you have photographs taken at the time.

"And that means we can reconstruct digitally, and 3D print, objects that no longer exist."

Dr Paul Barrett, a dinosaur expert from London's Natural History Museum, said this was a "neat study".

"It has allowed the [team] to recover important data previously thought to be irrevocably lost," he told BBC News.

"These dinosaur track sites are of major historical importance, and being able to retrieve this level of information 70 years after they were broken up and dispersed is a nice outcome."