PALEONTOLOGY MARVEL: Istiorachis macarthurae – The Strange “Sail-Backed” Dinosaur That Used Its Spine Sail for Flirting and Intimidating Rivals!

A newly named Early Cretaceous iguanodontian has taken the dinosaur world by storm. Istiorachis macarthurae, a one-tonne “sail-back” relative of Iguanodon, sported dramatically elongated neural spines along its back and tail, forming a striking sail-like structure likely used for both Sєxual display (“flirting”) and rival intimidation.

Described in August 2025 from a partial skeleton found in the ~125-million-year-old WesSєx Formation on England’s Isle of Wight, the dinosaur was formally named Istiorachis macarthurae (“sail spine of MacArthur”) in honour of British sailor Dame Ellen MacArthur. The find was made by the late amateur palaeontologist Nick Chase and studied by Jeremy Lockwood and colleagues at the University of Portsmouth and Natural History Museum.

Its hyper-elongated dorsal and caudal spines represent one of the most extreme examples of neural-spine elongation in iguanodontians. Ancestral-state reconstructions show modest elongation began in ankylopollexians during the Late Jurᴀssic, with hyper-elongation appearing sporadically—especially in the Barremian. The sail was probably covered in skin and brightly coloured in life, serving as a visual signal.

Researchers propose a pluralistic function: the structure could attract mates through impressive displays while also intimidating compeтιтors or signalling species idenтιтy. This mirrors hypotheses for other sail-backed dinosaurs like Ouranosaurus and Spinosaurus, but Istiorachis provides fresh evidence that display, rather than thermoregulation, was the primary driver in ornithopods.

As the latest in a wave of new Wealden dinosaurs from the Isle of Wight, Istiorachis highlights how these medium-sized herbivores experimented with flamboyant anatomy during the Early Cretaceous. The “sail king” of the WesSєx has arrived—and its striking spine is rewriting the story of dinosaur courtship and combat.