The hadrosauroid dinosaur Pararhabdodon isonensis is known from partial cranial and postcranial material from the Maastrichtian of the south Pyrenean foredeep basin (northern Catalunya, Spain). We revise and emend the taxonomic history, stratigraphic context, osteology, and systematic position of this taxon. Our study leads us to rediagnose P. isonensis on the basis of a maxilla that combines an extremely elevated jugal joint with a subvertical and concave lateral surface of the maxilla ventral to the jugal joint, as well as a craniocaudally broad dorsal process; and a proximal half of the humerus medially offset 30° from its long axis. Our parsinomy heuristic analysis of P. isonensis and 22 other iguanodontoideans infers the phylogenetic position of the former as the sister taxon to Hadrosauridae (restricted here to the clade comprising Hadrosaurinae and Lambeosaurinae). One dentary, previously referred to P. isonensis, was collected at a site that is both stratigraphically and geographically separated from the type locality of P. isonensis. The dentary becomes the holotype of a new taxon, Koutalisaurus kohlerorum, on the basis of a uniquely elongated and medially projecting edentulous portion. This results in a distance between the symphysis and the lateral wall of the dentary that is three times the mediolateral breadth of the bone. K. kohlerorum shares with other hadrosauroids a tooth row that extends caudal to the apex of the coronoid process and, with Hadrosauridae, a tooth row that is, in occlusal view, straight and parallel to the lateral face of the dentary.