A new genus and species of sailed Iguanodontian dinosaurs has been discovered from a partial skeleton unearthed in the Wessex Formation on the Isle of Wight, England.

Named Istiorachis macarthurae, this new dinosaur species thrived in what is now England during the early Cretaceous period, approximately 125 million years ago.

These ancient creatures were part of a large, widely distributed group of herbivorous dinosaurs known as iguanodontians.

“Iguanodontia represented a highly successful clade of Ornithischian dinosaurs,” said Jeremy Lockwood, a paleontologist from the University of Portsmouth and the Museum of Natural History in London.

“By the end of the Cretaceous, they dominated the dinosaur fauna of Laurasia, alongside the hadrosaurid family, including Edmontosaurus legatus and Parasaurolophus walkeri.”

“While diversity among iguanodonts was low during the late Jurassic, it surged in the early Cretaceous.”

The most notable characteristic of Istiorachis macarthurae is a series of elongated spines along its back and tail, which formed a large sail-like structure.

“Evolution often favors the extravagant over the practical,” Lockwood commented.

“The precise function of such structures has been debated for years; however, while they may serve purposes from heat regulation to fat storage, visual signaling—perhaps for sexual display—seems the most plausible explanation in this context.”

“In modern reptiles, such sail structures are often more pronounced in males, indicating that these traits may have evolved to attract mates or intimidate rivals.”

“We hypothesize that Istiorachis macarthurae may have done something similar.”

Paleontologists closely examined the fossilized bones to determine the purpose of the sails.

By creating a comprehensive database of similar dinosaur backbones through direct observations, photographs, scientific illustrations, and reconstructions, they were able to investigate the evolutionary history of the back structure in this new Iguanodontian family tree.

This helped identify broader trends in the evolution of these sails.

“These methods allow us not only to explain the fossil evidence but also to test hypotheses about their function,” Lockwood noted.

“We demonstrated that Istiorachis macarthurae‘s spines were not only taller but also more exaggerated compared to typical Iguanodon features, making it an ideal candidate for traits arising through sexual selection.”

Istiorachis macarthurae illustrates a broader evolutionary pattern.

Research indicates that the lengthening of neural spines in the Iguanodon lineage began in the late Jurassic period, becoming more common in the early Cretaceous.

However, true hyperelongation, which surpasses four times the height of the spine body, remains rare.

Similar displays can be observed in present-day reptiles, such as various lizard species, where elaborate crests and sails often communicate health and strength to potential mates.

“Istiorachis macarthurae is a prime example,” Lockwood said.

The findings were published in the journal Paleontology Papers this week.

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Jeremy A. F. Lockwood et al. 2025. The origin of neural spine elongation in Iguanodontian dinosaurs and the osteology of the new sail-backed dinosaur (Dinosaur, Ornithischia) from the Cretaceous Wealden group in England. Paleontology Papers 11(4): E70034; doi: 10.1002/spp2.70034