400 m year old fossils show how fish may have started to walk

Researchers from the University of the West of England have found the fish trails in rocks that were once a riverbed, but are now in the heart of the Brecon Beacons. The site of the sandstone quarry was once a river, and the landscape would have been very different from today – instead of moors and hills, there would have been semi-desert around a wide, shallow water course.

A new Research-TV film called Follow that Fish! shows the researchers investigating the fossils in the sandstone. One group of fish, the cephalaspids, looks unlike any freshwater fish known today, with a unique, horseshoe-shaped head shield and a very different arrangement of fins. Dr Susan Marriott, a floodplain specialist from UWE’s Faculty of the Built Environment, believes the fossilised trails, in what was once river sediment, could unlock the mystery of how these fish moved.

She said: “One of the most important things at this time in geological history was the emergence of life from a watery environment into a land environment. We have found fossils and the traces of the animals that made them, from which we can make inferences about the environment the animals lived in and link it to the evolution of life on land.”

For the film, UWE researcher Lance Morrissey from the School of Geography and Environmental Management suggested that animators from UWE’s School of Animation draw moving sequences, based on the trails left behind and preserved in stone, to show how these early vertebrates may have behaved. The fish making the trails appear to have used their pectoral fins to rest on the sediment before taking off – this could be the start of rudimentary limbs that would one day walk on land.

He said: “The Old Red Sandstone was well known for preserving the fossils of the fish. But the fish trails and their significance have never been recorded before.”