The osteohistology of new remains of Pararhabdodon isonensis sheds light into the life history and paleoecology of this enigmatic European lambeosaurine dinosaur

Abstract

Pararhabdodon isonensis was the first species of lambeosaurine hadrosaurid described in Europe and is one of the last non-avian dinosaurs that lived before the K-Pg extinction. Yet, its relationship with other Ibero-Armorican lambeosaurines has remained controversial due to the lack of overlapping diagnostic material among taxa. Newfound hindlimb materials reveal a unique character for the species that reinforces its distinction from other European lambeosaurines and its postulated close relationship with Tsintaosaurus spinorhinus. P. isonensis becomes restricted to the upper Maastrichtian Talarn Formation.Our osteohistological analysis indicates that Pararhabdodon isonensis probably reached adult body sizes comparable to those of other Ibero-Armorican lambeosaurines and nearing the body sizes of North American and Asian taxa. Its histomorphology indicates a relatively low growth rate, suggesting the achievement of larger body sizes over longer time periods, perhaps facilitated by a relatively low predation pressure. Unlike coeval dinosaurian clades of the Late Cretaceous European Archipelago, P. isonensis and at least some of the other Ibero-Armorican lambeosaurines that reached similarly large body sizes, like Adynomosaurus arcanus, represent exceptions to the ‘island rule’.