The Natural History Museum announced a new iguanodontian dinosaur, Istiorachis Macarthurae, whose back carried a sail of neural spines rising 10–12 inches. The formal description appeared in the journal Papers in Palaeontology.
Jeremy Lockwood, a retired general practitioner now pursuing a Ph.D. with the University of Portsmouth and the museum, identified the animal after re-examining bones collected on the Isle of Wight about 40 years ago. “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,” said Lockwood. “No one had really taken a close look at these bones before,” he added.
Detailed measurements and comparisons with hundreds of iguanodontian vertebrae showed that the spines were far taller than those of any other British iguanodontian. “We showed that Istiorachis’s spines weren’t just tall—they were more exaggerated than is usual in iguanodontian dinosaurs, which is exactly the kind of trait you’d expect to evolve through sexual selection,” said Lockwood. He remarked that “evolution sometimes seems to favor wastefulness over practicality.”
Istiorachis macarthurae roamed the coastal floodplains of what is now the Isle of Wight about 125 million years ago, stood roughly two metres high and weighed around one tonne. The genus name means sail spine, and the species name honors Isle of Wight sailor Dame Ellen MacArthur, who set a solo round-the-world sailing record in 2005 CE. “It is both extraordinary and a huge honor that a creature living 125 million years ago could possibly be linked to my family name,” said MacArthur.
To investigate the sail’s purpose, Lockwood compared the fossil with a broad sample of iguanodontian backbones and rejected heat regulation or fat storage. “In modern reptiles, sail structures often show up more prominently in males, suggesting that these attributes evolved to impress mates or intimidate rivals. We think Istiorachis may have been doing much the same,” he said. He argued that a blood-rich thermoregulatory sail “would be very vulnerable to attacks and could cause massive blood loss if damaged”.
Professor Susannah Maidment of the Natural History Museum, a co-author of the study, praised the work. “Jeremy’s careful study of fossils that have been in museum collections for several years has brought to life the iguanodontian dinosaurs of the Isle of Wight,” she told Phys.org. Maidment noted that Lockwood’s efforts over five years have quadrupled the number of smaller iguanodontian species recognized on the island, underscoring how much remains to be learned about Early Cretaceous ecosystems in the United Kingdom.
The Isle of Wight has yielded at least ten new dinosaur species in six years. “I am sure that in the coming years there will be even more,” said Lockwood, quoted by LIFO.
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