Why the Jurassic Coast and Isle of Wight Are Fossil Hotspots

A rare fragment of the world’s oldest marine crocodile was recently recovered by an amateur fossil hunter in Lyme Regis, underscoring the exceptional fossil deposits of the Jurassic Coast and the Isle of Wight.

During the early Jurassic period, ichthyosaurs and plesiosaurs dominated the seas that covered what is now Dorset, accompanied by diverse smaller marine life.

By the Cretaceous period, the Isle of Wight represented “the acme of dinosaur diversity in the UK,” said palaeontologist Dr. David Button, curator and general manager of the Dinosaur Isle Museum, with specimens spanning nearly every shape and size.

The unique geology of both areas – where constant coastal erosion exposes new fossils – explains the wealth of discoveries.

“If you’ve got a house on the tip of a cliff you don’t like erosion but if you’re a palaeontologist you do like erosion,” said Dr. Paul Davis, geology curator at Lyme Regis Museum.

At inland sites such as Oxfordshire, where the remains of the first dinosaur were found, spectacular traces of prehistoric reptiles typically emerge in quarries.

Coastal erosion along the Jurassic Coast – a UNESCO World Heritage Site stretching about 95 miles (153 km) from Old Harry Rocks in Dorset to Exmouth in East Devon – continuously reveals specimens representing the entire Age of Reptiles: the Triassic, Jurassic and Cretaceous periods.

Most finds are marine creatures, remnants of the warm tropical sea that once covered the region.

Regarding the Isle of Wight, Button said it is easier to list the dinosaurs that did not live there.

“If you came here about 125 million years ago you’d see all the main dinosaur groups apart from horned dinosaurs, dome-headed dinosaurs and Stegosaurs,” he said.

Recent discoveries include the remains of Europe’s largest-ever land-based predator dinosaur, dubbed the “white rock spinosaurid,” as well as the Comptonatus and the Istiorachis.

In Dorset, the huge skull of a pliosaur was extracted from cliffs in Kimmeridge Bay, and a tourist in Lyme Regis found the upper jawbone fossil of a Jurassic crocodile.

“We’ve got a lovely slice through the layer cake of essentially pretty much all of the Mesozoic era,” said Davis, adding that smaller specimens are more common.

“Most life in the ocean is not massive, big creatures,” he explained.

“For every whale, there are millions and millions and millions of shells.”

“Soft-bodied things rarely do preserve in the fossil record because they decay away or they get eaten, basically they rot or get stuffed down something else’s throat as a food source.”

A visit to Lyme Regis could yield bivalve shells such as mussels or cockles, snails, or the extinct ammonite – described by Davis as “a coily shell that had a squid-type creature living in the end of the aperture, and these things were super-numerous in the Mesozoic oceans.”

The ammonite also lent its name to the Kate Winslet-starring film about self-taught palaeontologist Mary Anning, now an iconic historical figure in Lyme Regis.

At the top of the food chain, apex predators are also preserved.

“If you’ve gone up into the reptiles, the commonest thing are ichthyosaurs,” Davis said.

“These were probably the most abundant large predator. We’re talking the top of the food web here.”

“Rarer than the ichthyosaurs are plesiosaurs and pliosaurs, which are very closely related.”

“These things started out looking like the Loch Ness Monster with a big fat body, four flippers, a long snake-like neck with a small little head.”

“These plesiosaurs evolved into the pliosaurs, with the same sort of body plan except the neck became shorter, and the head became bigger, and they became a very large size.”

“But you can get dinosaurs washed in. Dinosaurs aren’t a marine creature but things living on land do get washed out to sea.”

“And we have pterosaurs, which were flying reptiles, those occasionally do get preserved in the marine rocks.”

“Obviously these things were fishing and eating fish in the sea and, again, you would occasionally find bones of those but these are rare.”

During the early Cretaceous period, the Isle of Wight was connected to mainland Europe and was a hub of activity, with more than 25 different dinosaur species.

Many are preserved in the Wessex Formation, a rock layer along an 11-mile (17.7 km) stretch of coastline between Compton and Sandown.

“We’ve got carnosaurs, sauropods, ornithopods, tyrannosauroids, spinosaurs, we’ve got several kinds of theropods,” Button said.

“We’ve even got some raptors, like probable dromaeosaurs – overall it’s a really impressive sample of dinosaurs.”

He described the prehistoric environment as “a very rich and diverse environment” with a “Mediterranean-type climate of two main seasons – a hot, dry season and a mild-to-wet season.”

This abundance means visitors have a strong chance of making their own special find on these beaches.

Davis recommended an official fossil walk with his museum as a starting point; guides there currently take out 6,000 people each year.

“It’s not only us, Charmouth Heritage Coast Centre do it, there are other private guides as well. Book onto one of those, they will show you what to look for and how to find fossils,” he said.

“Once you’ve been shown, you are then free to explore. You will have been shown and given the tips on how to do it safely.”

Charmouth and Lyme Regis beaches are the best locations for fossil hunting.

Button recommended Compton Bay, which features a large number of dinosaur footprints, as well as Yaverland, and noted there are many more sites.

“What we’d say to amateurs is to focus on looking for loose material on the beach that can be picked up,” he suggested.

“Leave anything that is embedded that will require extraction for the sustainability of the site and for the safety of the specimen, to make sure that it’s not damaged.”

“It’s common to find rolled pieces of bone that have been in the sea and spat out again… but also people find identifiable dinosaur bones quite regularly as well,” he added.

“So if you go out looking at the beaches, it’s not too uncommon at all to find a dinosaur bone.”