Comptonatus chasei roamed island 125m years ago and is most complete dinosaur fossil found in UK in a century

A new species of large plant-eating dinosaur that roamed the Isle of Wight about 125m years ago has been identified.

The specimen, which weighed as much as an African elephant, represents the most complete dinosaur discovered in the UK in a century with 149 bones in total, researchers said.

Comptonatus chasei, named after the late fossil hunter Nick Chase and the place where it was found, the cliffs of Compton Bay, belongs to a group of herbivorous dinosaurs known as iguanodontians, bulky creatures often described as the “cows of the Cretaceous period [145-66 m years ago]” by palaeontologists.

Jeremy Lockwood, a PhD student at the University of Portsmouth, said: “This animal would have been around a tonne (1,000kg), about as big as a large male American bison.

“Evidence from fossil footprints found nearby shows it was likely to be a herding animal, so possibly large herds of these heavy dinosaurs may have been thundering around if spooked by predators on the floodplains over 120m years ago.”

For the study, published in the the Journal of Systematic Palaeontology, the researchers analysed every part of the fossil, including skull, teeth, spine and leg bones as well as a pubic hip bone “about the size of a dinner plate”.

Lockwood said it was unclear why the hip bone, found at the base of the abdomen, was so big, but added: “It [the bone] was probably for muscle attachments, which might mean its mode of locomotion was a bit different, or it could have been to support the stomach contents more effectively, or even have been involved in how the animal breathed, but all of these theories are somewhat speculative.”

When Comptonatus was discovered, the specimen was thought to be a different type of dinosaur called Mantellisaurus, three-toed plant-eaters that lived in Britain more than 120m years ago.

But Lockwood said Comptonatus differed from Mantellisaurus because of the “unique features in its skull, teeth and other parts of its body”.

He said: “Its lower jaw has a straight bottom edge, whereas most iguanodontians have a jaw that curves downwards.”

Dr Susannah Maidment, a senior researcher and palaeontologist at the Natural History Museum, said Comptonatus demonstrated fast rates of evolution in iguandontian dinosaurs during that time period.