A new iguanodontian (Dinosauria: Ornithopoda) from the Lower Cretaceous Kitadani Formation of Fukui Prefecture, Japan

Abstract

ABSTRACT The skull material of a new iguanodontian dinosaur, Fukuisaurus tetoriensis gen. et sp. nov., discovered from the fluvial deposits of the Lower Cretaceous Kitadani Formation, Tetori Group, Fukui Prefecture, Japan, is described here. Some features of Fukuisaurus show affinities with Iguanodon, Ouranosaurus, and Altirhinus, referred to as Iguanodontidae by some. A phylogenetic analysis using mainly cranial characters shows that Fukuisaurus is a definitive derived non-hadrosaurid iguanodontian and implies that Fukuisaurus is more derived than the clade of Iguanodon + Ouranosaurus and more basal to the clade of Altirhinus, Probactrosaurus, Eolambia, Protohadros, Bactrosaurus, Telmatosaurus, and hadrosaurids. It also supports that Iguanodontidae is paraphyletic by the exclusion of Altirhinus as suggested previously. The presence of Fukuisaurus indicates a wider geographical distribution of the group in eastern Asia. The occurrences of derived non-hadrosaurid iguanodontians from the Kitadani Formation and other formations in Japan support a dispersal of this group into eastern Asia by the Early Cretaceous and its temporal range extension in Japan. Fukuisaurus possesses a strong maxilla-vomer articulation, indicative of the independent acquisition of a non-pleurokinetic skull (not present in Hypsilophodon, Iguanodon, and hadrosaurids).