Data from: The origins of neural spine elongation in iguanodontian dinosaurs and the osteology of a new sail-back styracosternan (Dinosauria: Ornithischia) from the Lower Cretaceous Wealden Group of England

The Wealden Group of southern England was deposited during the late
Berriasian into the early Aptian. It records a critical time in the
development of iguanodontian dinosaur diversity, from the low levels of
the Jurassic to the higher levels in the Aptian and Albian. A new
iguanodontian dinosaur, Istiorachis macarthurae gen. et sp. nov. from the
Wessex Formation (Wealden Group) of the Isle of Wight, exhibits
hyperelongation of the dorsal and caudal neural spines, suggesting that it
possessed a possible sail structure. Ancestral state reconstruction for
the relative height of dorsal neural spines in iguanodontians reveals that
modest elongation began with Ankylopollexia in the Late Cretaceous and
elongation became established during the Cenomanian stage of the Late
Cretaceous, albeit with widely disparate values. Hyperelongation of neural
spines occurred sporadically throughout the Cretaceous, being most
frequently recorded in the Barremian and early Aptian. Possible
explanations for neural spine elongation in Ankylopollexia include
biomechanical advantage, perhaps related to greater mass and a locomotory
shift towards quadrupedalism, and visual signalling either driven by
sexual selection or species recognition. The function of elongate neural
spines was probably pluralistic and differed in different taxa. No single
explanation fully supports the variation seen throughout the Cretaceous.