A revision of the non-avian dinosaurs ‘Eucercosaurus tanyspondylus’ and ‘Syngonosaurus macrocercus’ from the Cambridge Greensand, UK

Abstract

The Cambridge Greensand Member (lower Cenomanian: Upper Cretaceous) has yielded a diverse fauna of terrestrial and marine tetrapods, whose remains are largely reworked from the underlying Gault Formation (upper Albian: Lower Cretaceous). Here, we re-describe two of the non-avian dinosaur taxa named from this unit, ‘Eucercosaurus tanyspondylus’ Seeley, 1879 and ‘Syngonosaurus macrocercus’ Seeley, 1879, both of which have been referred to as either ankylosaurs or ornithopods but whose validity has not been rigorously assessed for over a century. Both taxa are interpreted as the remains of iguanodontian dinosaurs but possess no clear diagnostic features. Nevertheless, although ‘Eucercosaurus’ and ‘Syngonosaurus’ are nomina dubia they do indicate that iguanodontians were common components of the Cambridge Greensand tetrapod fauna and, alongside ‘Trachodon cantabrigiensis’ Lydekker, 1888, represent an important datum for understanding iguanodontian distributions during the mid-Cretaceous.