Footprints discovered on a South Wales beach could have been made more than 200 million years ago by an early relative of a dinosaur, experts believe.

Palaeontologists at the Natural History Museum believe the footprints – known as a trackway – were most likely left by a very early sauropod or a prosauropod.

They were discovered on a beach in Penarth, Vale of Glamorgan, in 2020 by amateur palaeontologist Kerry Rees, who reported her find to the Natural History Museum.

Dr Susannah Maidment and Professor Paul Barrett were initially sceptical of the report but after carrying out an investigation, they believe the find is from an early relative of a dinosaur, dating from the Triassic period.

Dr Maidment said: “We get a lot of inquiries from members of the public for things that could be trackways but many are geological features that can easily be mistaken for them.

“However, from the photographs, we thought they were a fairly good contender for something that could be tracks and that it would be worth taking a look.”

Prof Barrett said: “We believed the impressions we saw at Penarth were consistently spaced to suggest an animal walking.

“We also saw displacement rims where mud had been pushed up. These structures are characteristic of active movement through the soft ground.”

Less visible were toe marks – the tell-tale sign of an animal footprint.

A previous survey of the site 10 years ago had taken photographs with less weathering which showed features like toe impressions.

This not only provided the team further evidence that the impressions were indeed footprints but also suggested what the identity of the animal making them might have been.

The team now think the impressions are an example of Eosauropus, which is a name not of a dinosaur but a type of track thought to have been made by a very early sauropod or near sauropod-relative, the group of dinosaurs that later included the famous Diplodocus.

Dr Maidment said: “We know early sauropods were living in Britain at the time, as bones of Camelotia, a very early sauropod, have been found in Somerset in rocks dated to the same period.

“We don’t know if this species was the track maker, but it is another clue which suggests something like it could have made these tracks.”

Dinosaur trackways can provide a wealth of behavioural information and can show movement in herds and provide data on the way an animal may have walked.

Prof Barrett added: “These types of tracks are not particularly common worldwide, so we believe this is an interesting addition to our knowledge of Triassic life in the UK.

“The record of Triassic dinosaurs in this country is fairly small, so anything we can find from the period adds to our picture of what was going on at that time.”

The Penarth trackways have been documented for future study using 3D imaging techniques, while they will remain on the shore until the tide eventually erodes them away.

– The findings, Late Triassic dinosaur tracks from Penarth, South Wales, are published in the journal Geological Magazine.