The identification of avian and dinosaurian digits remains one of the major controversies in vertebrate evolution. A long history of morphological interpretations of fossil forms and studies of limb development in embryos has been given as evidence for two differing points of view. From an originally pentadactyl forelimb, either digits I, II and III form in the manus of birds and thus support a dinosaurian ancestry, or digits II, III and IV form in the manus supporting a more ancient ancestry or an evolutionary frameshift. A review of the history of research into the subject is presented here, dating from approximately 1825 to 2009.