Arenysaurus is a genus of hadrosaurid dinosaur from the Late Cretaceous (66 million years ago). It is known from a partial skull and skeleton found in late Maastrichtian-age rocks of the Pyrenees Mountains in Spain. The type species is A. ardevoli, described in 2009 by Pereda-Suberbiola et al., a group of researchers from Spain. The genus name refers to Arén, where it was found, and the specific epithet honours geologist Lluís Ardèvol. The estimated body length of Arenysaurus is 5 to 6 metres (16 to 20 ft). Arenyosaurus was a lambeosaurine, a member of the hadrosaurid subfamily with hollow cranial crests. Arenysaurus is one of the most complete and best dated ever found in the Late Cretaceous period.