Ankylopollexia is an extinct clade of dinosaurs within the Ornithischia. They lived from 156 to 66 million years ago. The name stems from the Greek word, “ankylos”, meaning stiff, fused, and the Latin word, “pollex”, meaning thumb. One of the most famous and most derived members of the Ankylopollexia clade is the "Iguanodon". The Hadrosaurs are also in this group.