Dinosaur tracks on Welsh beach are evidence of sauropod gathering

Fossils reported by the public suggest early sauropods once roamed the land which is now Wales. 

Researchers at the Museum were alerted to impressions left behind over 200 million years ago on the beach at Penarth, south of Cardiff, by a member of the public. Although thought by some to be the result of geological processes, it has now been suggested that they could be dinosaur tracks. 

Their large size and shape suggest that they could belong to a large sauropodomorph dinosaur. While the footprints can't be linked to an exact species, it could have been one similar to Camelotia, a Triassic dinosaur named after King Arthur's castle and whose fossils have been found in southwest England from rocks dated to a similar period of time. 

Prof Paul Barrett, who researches dinosaurs at the Museum and co-authored the paper, says that the number of footprints makes it possible the site was a place where sauropods gathered. 

'There are hints of trackways being made by individual animals, but because there are so many prints of slightly different sizes, we believe there is more than one trackmaker involved,' he says. 

'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. Our 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 findings of the study, carried out by scientists across the UK and France, was published in the journal Geological Magazine.

Following in the footsteps of giants

While the most recognisable fossils come from the preserved bones of ancient animals, their activity can also occasionally be preserved. 

If the conditions are right when walking on soft sediments like mud or sand, footprints can be left behind. These tracks can then be baked dry by the Sun and then filled in by other sediments making them more likely to form trace fossils, which are also known as ichnofossils. 

'Trace fossils are those that capture aspects of an animal's behaviour or anatomy which aren't captured by its skeleton,' Paul explains. 'This can include trackways, coprolites, burrows and gut contents, which represent the animal interacting with its environment or the materials it produces.  

'They're often not associated with a specific species except in very rare circumstances, but they can be quite common as things like footprints are created thousands of times during a single animal's lifetime.' 

As rocks are uplifted and eroded through time, tracks which have been buried for millions of years can be brought to the surface. Many are found near bodies of water as the rock surrounding them is eroded away revealing the fossils underneath. 

The ichnofossils at Penarth have come to light periodically over the years, with the first recorded finds dating back to at least 1879. However, the shifting sand and pebbles have covered and uncovered the impressions over the years, leaving them to be rediscovered time after time. 

More recently, scientists from the National Museum of Wales, Cardiff University and the University of Lyon, had documented the tracks and came up with their own theories, but none of this research was published. However, hundreds of photos were taken which proved invaluable for the current study. 

After a member of the public, Kerry Rees, got in touch with the Angela Marmont Centre about the tracks in 2020, Museum scientists headed down to document the site. While there, they found out about the previous work by other researchers, with many of the scientists agreeing to team up to collaborate on this paper. 

The scientists have now described the two stretches of trackways in unprecedented detail, giving hints about the animals which roamed in Wales' ancient past. 

A step back in time

Using photos taken at the site, the researchers produced an extraordinarily detailed 3D model to examine the impressions in more detail. But being exposed to the elements meant much of the rock had been worn away and its finer details lost. 

Lead author Dr Peter Falkingham says, 'The tracks initially seemed a bit non-descript, and it took us quite a while to decide if they really were tracks or just holes in the ground.  

'When we looked closely, it seemed that the impressions would overlap in places, as would be expected if multiple animals were trampling the ground. They also seemed to sometimes occur in semi-regular spacing as you'd expect from a trackway. 

'The best evidence actually came from a track that isn't there anymore but was documented in 2009, which I used to build a 3D model of the site. One of the tracks visible in that model had what we interpreted as digit impressions, and that sealed the deal for us that they were indeed tracks.' 

However, while shapes like these may look like footprints, there are some natural processes that can produce footprint-like impressions.  

For instance, minerals like gypsum can be dissolved away and leave footprint-like cavities, while small mud volcanoes can produce what looks like the rim of a footprint. Other animal behaviour can also be responsible, with some potential fossil tracks being explained as impressions left by the feeding of ancient rays. 

However, the structure of the impressions in Penarth convinced the scientists that these are bona fide tracks. While their condition makes it hard to assess whether the tracks come from one or more species, there are some inferences that researchers can make. 

The muddle of different tracks suggests that the fossils are the remains of a trample ground, where many dinosaurs gathered together. These are often found along herd movement routes and bodies of water where many animals would be found close together. 

Their position in the rocks suggests they were formed in the Late Triassic between 237 and 201 million years ago, while the narrowness of the tracks indicates they were probably made by a biped. 

'We think the tracks are an example of Eosauropus, which is not the name of a particular dinosaur species but for shape of a type of track thought to have been made by a very early sauropod or a prosauropod,' Paul says. 'We know these kinds of dinosaur were living in Britain at the time, as bones of the sauropod Camelotia have been found in Somerset in rocks dated to the same age.  

'We don't know if this species was the track maker, but its presence nearby was another smoking gun which suggested something like it could have made these tracks.' 

While the tracks may continue under the sand and shingle on the beach, the scientists believe that the fossils are best left in the ground for now. Without a wider conservation plan in place, digging out the fossils may cause irreparable damage to them. 

Instead, they advocate mapping out the footprints as they are revealed, one step at a time.