New dinosaur species with striking sail-like back discovered

The dinosaur would have had an exaggerated sail-like feature on its back. (James Brown/University of Portsmouth via CNN Newsource)

Paleontologists have discovered a new dinosaur species with a very distinctive feature, a sail-like structure running down its back, the Natural History Museum in London announced on Friday.

The bones of Istiorachis macarthurae, named in honour of record-breaking British sailor Ellen MacArthur, were uncovered on the Isle of Wight, a small island just off the south coast of England, where it roamed more than 120 million years ago alongside other Iguanodon relatives — a group of herbivorous dinosaurs that lived from the Late Jurassic to Early Cretaceous periods.

Scientists aren’t exactly sure exactly why it had such an exaggerated sail-like feature on its back, though they hypothesize it might have helped the dinosaurs attract a partner and recognize each other as belonging to the same species.

Previously, this specimen, discovered about 40 years ago, was thought to belong to one of the two iguanodontian species known to have lived on the Isle of Wight.

But when retired doctor Jeremy Lockwood was re-examining the bones as part of his PhD studies, he realized that “this one had particularly long neural spines, which was very unusual.”

Identifying this distinctive sail-like feature helped define the dinosaur, which was around 2 metres (6.6 feet) tall and weighed around 1,000 kilograms (2,205 pounds), as a new species, Lockwood said in a statement. He published his findings in the journal Papers in Palaeontology on Thursday.

“The discovery of another iguanodontian from the Isle of Wight shows that this was a very diverse area in the Early Cretaceous,” he added. “I’m sure there’ll be more discoveries in the years to come.”

The Istiorachis macarthurae lived at a time when Iguanodon dinosaurs were evolving to develop taller and taller spines, he found.

“Partly, we think this was for muscle attachment,” Lockwood said.“Iguanodontians were changing from small bipedal dinosaurs into much bigger animals that spent more time on four legs, so they would have needed stronger muscular support for their backbones.”

Even in this context, the Istiorachis macarthurae’s backbone is unusual. Lockwood argues against one potential theory that the sail could have helped the dinosaur regulate its body temperature, saying that a “sail with a lot of blood vessels would be very vulnerable to attack and could cause massive blood loss if it was damaged.”

Instead, he believes that “sexual signalling is the most probable explanation,” meaning that the sail would fulfil a similar to a male peacock’s tail.

“When a characteristic is exaggerated beyond its practical function in living animals, it is invariably due to the evolutionary pressure to attract a mate. Istiorachis’ sail seems to be another example of that,” he added.

By Issy Ronald, CNN