CREECH, J.E.*; ERICKSON, G.M.: Enamel Microstructure of Chamaeleonids and the evolution of reptilian enamel prisms

Uromastyx is the only reptilian clade that evolved enamel prisms equable to those found throughout the Mammalia. As part of a study on the evolution of prismatic enamel we used scanning electron microscopy to characterize the microstructure of enamel in the chamaeleonidae, a sister taxon to Uromastyx. Specimens selected included: Brookesia superciliarus, Chameleo hoehnelii, Rhampholeon brevicaudata, Bradypodion pymilum, Chamaeleo namaquensis, and Chamaeleo melleri. These taxa are representative of the phylogenetic, trophic and morphological diversity within the group. The results revealed that all taxa have aprismatic parallel crystallite enamel and a defined basal unit layer. The amount of longitudinal wrinkling of the enamel varied between species, as did the crystallite relationships (presence or absence of crystallite bundling). These results do not support theories positing that dental occlusion and permanent dentitions facilitate prismatic enamel formation.