A few dinosaurs, such as Mononykus, have only one claw on it's hand. Most tyrannosaurids, including Tyrannosaurus rex, had two fingers on each hand. Other theropods (such as Allosaurus) had three clawed fingers. Some theropods, such as Ceratosaurus, had four clawed fingers. Hadrosaurs had four-fingered hands, and Iguanodon was one of the very few dinosaurs that had five fingers.