Hadrosauroidea is a clade or superfamily of ornithischian dinosaurs that includes the "duck-billed" dinosaurs, or hadrosaurids, and all dinosaurs more closely related to them than to Iguanodon. Many primitive hadrosauroids, such as the sail-backed Ouranosaurus, have traditionally been included in a paraphyletic (unnatural grouping) "Iguanodontidae". With cladistic analysis, the traditional Iguanodontidae has been largely disbanded, and probably includes only Iguanodon and perhaps its closest relatives.
The following taxonomy follows Ramírez-Velasco et al, 2012 unless otherwise noted.
The cladogram below follows an analysis by Wu Wenhao and Pascal Godefroit (2012).
Cladogram after Prieto-Marquez and Norell (2010).
A phylogenetic analysis performed by Ramírez-Velasco et al. (2012) found a big polytomy of all hadrosauroids which are more derived than Probactrosaurus but less derived than Hadrosauridae. The exclusion of Claosaurus, Jeyawati, Levnesovia, Nanyangosaurus, Shuangmiaosaurus and Telmatosaurus from the polytomy resulted in a more resolved topology. The cladogram below shows Huehuecanauhtlus phylogenetic position among other hadrosauroids following this topology (the relationships within Hadrosauridae are not shown).