Lanzhousaurus

Abstract: Delapparentia turolensis Ruiz-Omenaca, 2011 is the only iguanodont taxon erected in the Barremian of Spain. It is described on the basis of a partial postcranial skeleton discovered in the 1950s near the village of Galve (Teruel Province), within the Camarillas Formation. Recently, new remains from the same individual have been recovered, and these are described here. Furthermore, after first-hand examinations of the holotype, the phylogenetic position of this taxon has been analysed for the first time, and its diagnosis is emended. Delapparentia turolensis is a large-sized, basal iguanodont which presents an autapomorphic, unusually high axial neural spine and a unique combination of postcranial characters. The ilium morphology differs from that of other basal iguanodonts and relates Delapparentia to the Valanginian Barilium dawsoni from England, with whom it shares two synapomorphies. In our phylogenetic analysis Delapparentia is recovered in a polytomy with Kukufeldia , Lanzhousaurus , Barilium and the clade equivalent to Iguanodontoidea.

Abstract: Lanzhousaurus magnidens, a large non-hadrosauriform iguanodontian dinosaur from the Lower Cretaceous Hekou Group of Gansu Province, China has the largest known herbivorous dinosaur teeth. Unlike its hadrosauriform relatives possessing tooth batteries of many small teeth, Lanzhousaurus utilized a small number (14) of very large teeth (~10 cm long) to create a large, continuous surface for mastication. Here we investigate the significance of Lanzhousaurus in the evolutionary history of iguanodontian-hadrosauriform transition by using a combination of stable isotope analysis and CT imagery. We infer that Lanzhousaurus had a rapid rate of tooth enamel elongation or amelogenesis at 0.24 mm/day with dental tissues common to other Iguanodontian dinosaurs. Among ornithopods, high rates of amelogenesis have been previously observed in hadrosaurids, where they have been associated with a sophisticated masticatory apparatus. These data suggest rapid amelogenesis evolved among non-hadrosauriform iguanodontians such as Lanzhousaurus, representing a crucial step that was exapted for the evolution of the hadrosaurian feeding mechanism.