‘Striking sail' may have helped dinosaurs find mates, new fossil suggests

A new dinosaur with a dramatic sail along its back and tail has been identified from fossils found on the Isle of Wight in England - and it may have evolved its eye-catching look to impress potential mates.

The new iguanodontian dinosaur was identified by Jeremy Lockwood, a retired GP, as part of his PhD studies at the University of Portsmouth and the Natural History Museum, London. He made the discovery by carefully re-examining dinosaur bones held in the collections at the Dinosaur Isle museum, Isle of Wight. 

Until now, the fossil material, which is around 125 million years old, had been assumed to belong to one of the two known iguanodontian dinosaur species from the Isle of Wight. But Lockwood noticed something unusual.

"While the skeleton wasn’t as complete as some of the others that have been found, no one had really taken a close look at these bones before", Lockwood said. "It was thought to be just another specimen of one of the existing species, but this one had particularly long neural spines, which was very unusual."

On closer inspection, Lockwood realised the animal would have probably possessed a pronounced sail-like structure along its back, helping to set it apart from other dinosaurs found on the island. His findings are described in a new paper published today in the scientific journal Papers in Palaeontology (DOI: 10.1002/spp2.70034).

Jeremy has named the new dinosaur Istiorachis macarthurae after a famous Isle of Wight resident. The name Istiorachis means ‘sail spine’, while macaruthurae honours Dame Ellen MacArthur, the English sailor who in 2005 set a world record for the fastest solo non-stop voyage around the world on her first attempt and who comes from the Isle of Wight. 

Lockwood explained, "Evolution sometimes seems to favour the extravagant over the practical. While the exact purpose of such features has long been debated – with theories ranging from body heat regulation to fat storage – researchers believe that the most likely explanation in this case is visual signalling, possibly as part of a sexual display and this usually is because of sexual selection”.

The team studying the fossils included the Natural History Museum’s Prof. Susannah Maidment. Susannah commented, “Jeremy’s careful study of fossils that have been in museum collections for several years has brought to life the iguandontian dinosaurs of the Isle of Wight. His work highlights the importance of collections like those at Dinosaur Isle, where fossil specimens are preserved in perpetuity and can be studied and revised in the light of new data and new ideas about evolution.

“Over the past five years, Jeremy has single-handedly quadrupled the known diversity of the smaller iguanodontians on the Isle of Wight, and Istiorachis demonstrates we still have much to learn about Early Cretaceous ecosystems in the UK.”

Importantly, Istiorachis appears to highlight a broader evolutionary trend. Research shows that elongation of neural spines in iguanodontians began in the Late Jurassic, before becoming a relatively common feature during the Early Cretaceous. However, true hyper-elongation, where spines stretch to more than four times the height of the vertebral body, remains rare.

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