Premise of research. Many Ceratozamia species are closely related and form species complexes with great similarity among the component taxa, especially in juvenile stages. This, coupled with character loss in herbarium specimens, has resulted in debate regarding recognition and validation of the species. This study, focused on the four species comprising the Ceratozamia norstogii species complex from a morphological and leaflet anatomy viewpoint, was undertaken to clarify relationships among the four taxa in the complex.Methodology. For morphological variation, 29 individuals from one population of each of the four species was sampled for nine vegetative and six reproductive variables. For leaflet anatomical variation, leaflets were taken from five adult plants of each species held under cultivation for >5 yr under uniform conditions. Cross sections of leaflets and cuticular peels were obtained using standard plant histological techniques and examined under bright-field light microscopy. Cross sections of...