Plicidentine, infolded dentine around the pulp cavity at the base of a tooth, has been histologically characterized in sarcopterygians, basal tetrapods, and the actinopterygian Lepisosteus. Within amniotes, however, its phylogenetic distribution is much less well documented and its morphological variability has not been described, in spite of the fact that plicidentine is considered a synapomorphy of three major clades of amniotes (Neochoristodera, Ichthyosauria, and Varanoidea). In this study, we provide a summary of the taxonomic distribution of plicidentine in amniotes, and also describe the morphological variation encompassed by this term. We conclude that plicidentine, as defined here, has evolved independently several times in amniotes, and that each occurrence is histologically distinct.