Dinosaurs left footprints thanks to 'Goldilocks effect'

Scientists used computers to simulate dinosaurs leaving tracks

Dinosaurs left lasting footprints only when conditions were just right, scientists have claimed.

University of Manchester researchers used computers to simulate prehistoric creatures making tracks in different types of mud.

They found that soil conditions had to be perfect for different dinosaurs to leave fossil footprints behind.

Dubbed the "Goldilocks effect", scientists say it explains why tracks were left at some sites and not others.

"By using computer modelling, we were able to recreate the conditions involved when a 30-tonne animal makes a track," said palaeontologist Dr Peter Falkingham, who led the research team.

Computer modelling

"Now we can use this Goldilocks effect as a baseline for exploring more complicated factors such as the way dinosaurs moved their legs, or what happens to tracks when a mud is drying out."

Dinosaurs ranged vastly in weight from Brachiosaurus, weighing around 30 tonnes, to Compsognathus, which was the size and weight of a chicken.

Some sites only reveal tracks of larger dinosaurs

But different sites have yielded different tracks.

The Paluxy River site in Texas, USA - where one of the most famous sets of fossil prints was found - only reveals prints of larger dinosaurs.

Using computer modelling, the team simulated up to 20 different dinosaurs walking in different conditions.

What they found was that heavier dinosaurs only left lasting tracks in thick, shallow mud.

In deeper, softer mud, only lighter dinosaurs could leave prints while larger animals would become stuck and die.

The findings also suggest that significant sites such as Paluxy River could have been host to a larger number of creatures than the tracks themselves show.

"A skeleton is the remains of a dead animal; the footprints are the remains of a living animal, something made during life," said Dr Falkingham.

"That's what is absolutely fascinating for me about dinosaur footprints."

The research is published in the Journal of the Royal Society Interface.