Fig. 1. Coronal and sagittal sections of the vole molar show a distinct and complex morphology. The general appearance of the sagittal section is dependent on the position it is taken, unlike most of the coronal sections. Here we used the particular sagittal section as shown that runs through the middle of the molar. The developmental histories of the vole and mouse molar start similarly and are almost identical until cap stage. After this, the actions of the enamel knots result in a different folding pattern of the epithelium. This results in the intercuspal folds or loops in the vole molar that reach almost down to the base. In the mouse molar the cervical loop epithelium loses its crown fate, i.e. it loses the stellate reticulum, and switches to root. In the vole molar most cervical loop epithelium retains the crown fate except for three small areas that are converted to root fate. After completion of root formation the mouse molar has no functional cervical loop epithelium left (i.e. it is missing stellate reticulum) unlike the vole molar, where most of the cervical loop continues to generate crown. ERM, epithelial cell rests of Malassez; HERS, Hertwig's epithelial root sheath; bl, basal lamina; icl, intercuspal loop; iee, inner enamel epithelium; oee, outer enamel epithelium; si, stratum intermedium; sr, stellate reticulum; dashed circles indicate the cervical loop area.