A team of scientists from the University of Portsmouth and London’s Natural History Museum has uncovered a new species of dinosaur after re-examining 125-million-year-old fossils found on the Isle of Wight.
The new species belongs to a family of plant-eating dinosaurs known as iguanodontians and it’s the third of its kind to be found on the island just off England’s south coast.
However, unlike the island’s other two species of iguanodontians, this new species has a “striking sail” that runs along its back and tail. This sail may have been used in dazzling mating displays, say scientists involved in the study published last week in Papers in Palaeontology.
The sail-backed iguanodontian was identified by retired GP turned PhD student Dr Jeremy Lockwood and named Istiorachis macarthurae - a combination of the latin term for ‘sail spine’ and an homage to local legend Dame Ellen MacArthur, who broke the world record for the fastest solo non-stop sailing trip around the world in 2005.
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Lockwood made his discovery while examining fossils held in the collections of the Dinosaur Isle museum on the Isle of Wight.
The material that was later identified as belonging to a new species was originally assumed to belong to one of the two known iguanodontians from the island, but during his examination Lockwood noticed a few peculiarities.
“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,” said Lockwood in an associated press release. “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.”
The long neural spines, which are more than four times the height of the vertebral body in some instances, supported Istiorachis’s sail.
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To work out what purpose the sail served, Lockwood and co-authors David Martill and Susannah Maidment compared the back bones of the new species with those of other iguanodontians.
“We showed that Istiorachis’ spines weren’t just tall - they were more exaggerated than is usual in Iguanodon-like dinosaurs, which is exactly the kind of trait you’d expect to evolve through sexual selection,” said Lockwood. “In modern reptiles, sail structures often show up more prominently in males, suggesting these attributes evolved to impress mates or intimidate rivals. We think Istiorachis may have been doing much the same.”
Istiorachis highlights a broad evolutionary trend of increasingly elongated neural spines in iguanodontians. Lockwood and co-authors Martill and Maidment found evidence to suggest this trend started in the Late Jurassic and that elongated neural spines became a relatively common feature amongst iguanodontians in the following period, the Early Cretaceous.
Still, Istiorachis is special in terms of the hyper elongation of its neural spines - a real rarity amongst others of its kind. More so than other iguanodontians, Istiorachis was a born show-off.
Top image: Istiorachis macarthurae. Credit: University of Portsmouth, original artwork by James Brown.
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