A brand new genus and species of sail-backed iguanodontian dinosaur has been recognized from a partial skeleton discovered within the Wessex Formation of the Isle of Wight, England.
Life restoration of Istiorachis macarthurae. Picture credit score: James Brown.
Scientifically named Istiorachis macarthurae, the brand new dinosaur species lived in what’s now England through the Early Cretaceous epoch, some 125 million years in the past.
The traditional animal was a member of a big and biogeographically widespread group of herbivorous dinosaurs referred to as Iguanodontia.
“Iguanodontia was a extremely profitable clade of ornithischian dinosaurs, the earliest recognized instance being the dryosaurid Callovosaurus leedsi from the Center Jurassic Oxford Clay Formation of England,” mentioned Jeremy Lockwood, a paleontologist on the College of Portsmouth and the Pure Historical past Museum, London, and his colleagues.
“By the top of the Cretaceous, they dominated the dinosaur fauna of Laurasia because the duck-billed hadrosaurids, a bunch containing well-known species resembling Edmontosaurus regalis and Parasaurolophus walker.”
“Iguanodontian variety was low within the Late Jurassic however elevated all through the Early Cretaceous.”
Istiorachis macarthurae’s most putting characteristic is a sequence of extraordinarily elongated spines alongside its again and tail, which in all probability supported a big, sail-like construction.
“Evolution typically appears to favor the extravagant over the sensible,” Lockwood mentioned.
“Whereas the precise goal of such options has lengthy been debated — with theories starting from physique warmth regulation to fats storage — researchers consider that the almost certainly rationalization on this case is visible signaling, probably as a part of a sexual show and this often is due to sexual choice.”
“In fashionable reptiles, sail constructions typically present up extra prominently in males, suggesting that these attributes advanced to impress mates or intimidate rivals.”
“We predict Istiorachis macarthurae could have been doing a lot the identical.”
To work out what the sail may need been for, the paleontologists carried out a detailed examination of the fossilized bones.
They then created a big database of comparable dinosaur again bones from direct observations, pictures, scientific illustrations and reconstructions, and used it to hint the evolutionary historical past of the heights of again bones on a brand new household tree of iguanodontian dinosaurs.
This allowed them to identify broader developments in how these sails advanced.
“These strategies allow us to transfer past merely describing the fossil and really take a look at hypotheses about its perform,” Lockwood mentioned.
“We confirmed that Istiorachis macarthurae’s spines weren’t simply tall — they have been extra exaggerated than is common in Iguanodon-like dinosaurs, which is strictly the form of trait you’d anticipate to evolve by way of sexual choice.”
Istiorachis macarthurae seems to spotlight a broader evolutionary pattern.
Analysis exhibits that elongation of neural spines in iguanodontians started within the Late Jurassic, earlier than changing into a comparatively widespread characteristic through the Early Cretaceous.
Nevertheless, true hyper-elongation, the place spines stretch to greater than 4 instances the peak of the vertebral physique, stays uncommon.
Comparable shows are seen in residing reptiles at this time, together with a number of species of lizard, the place elaborate crests and sails usually sign well being and power to potential mates.
“Istiorachis macarthurae is a deep-time instance of the identical evolutionary pressures we see shaping show constructions in fashionable animals,” Lockwood mentioned.
The findings have been revealed this week within the journal Papers in Palaeontology.
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Jeremy A.F. Lockwood et al. 2025. The origins of neural backbone elongation in iguanodontian dinosaurs and the osteology of a brand new sail-back styracosternan (Dinosauria, Ornithischia) from the Decrease Cretaceous Wealden Group of England. Papers in Palaeontology 11 (4): e70034; doi: 10.1002/spp2.70034
