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A retired physician’s reexamination of a 125-million-year old fossil specimen has unexpectedly yielded an entirely new dinosaur species. After careful analysis, it appears that the United Kingdom was once home to an iguanodontian featuring a distinctively massive, sail-like fin along its back. And naturally, its discoverer named it after a local sailing hero.

For the past few years, former general practitioner Dr. Jeremy Lockwood has combed through archival fossil troves as part of his ongoing Ph.D research at the University of Portsmouth and the Natural History Museum, London. While perusing the Dinosaur Island museum’s collection on the Isle of Wight, Lockwood noticed something peculiar about a set attributed to one of the island’s two known iguanodontian species.

“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,” he explained in a statement. “This one had particularly long neural spines, which was very unusual.”

The anterior-most seven caudal vertebrae in left lateral view with neural spines reconstructed. Credit: Papers in Palaeontology

Further analysis led Lockwood and colleagues to confirm the bones belonged to its own dinosaur species, which they named Istiorachis macarthurae and describe in a study published August 21 in the journal Papers in Palaeontology. While Istiorachis translates to “sail spine,” macarthurae is intended as a tribute to Dame Ellen MacArthur. A native of the Isle of Wright, MacArthur made history in 2005 when she set the world record for the fastest solo, non-stop voyage around the world—and on her first attempt, nonetheless.

Istiorachis appears to have been slightly taller than an adult human, with neural spines growing as long as 10 to12 inches. Why it boasted such a large dorsal accessory remains a bit of a mystery. According to Lockwood, there may be multiple explanations. Similar to male peacock’s ostentatious fan of tail feathers, I. macarthurae may have showed off its back fin as part of a sexual display.

“Evolution sometimes seems to favor the extravagant over the practical,” Lockwood said. “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 signaling.”

I. macarthurae stood slightly taller than an adult human. Credit: Papers in Palaeontology

Istiorachis seems to showcase a larger evolutionary theme for dinosaurs. Previous studies indicate iguanodontians first began displaying elongated neural spines during the Late Jurassic. By the Early Cretaceous, the physical detail had become far more common.

This isn’t Lockwood’s first paleontological discovery, either.

“Over the past five years, Jeremy has single-handedly quadrupled the known diversity of the smaller iguanodontians on the Isle of Wight,” said study co-author and Natural History Museum paleontologist Susannah Maidment. “Istiorachis demonstrates we still have much to learn about Early Cretaceous ecosystems in the UK.”