Crown characteristics have been the parameter most frequently utilized in studies of tooth morphology. Dental root structures have received relatively little attention. Examination of unusual molar roots in a kindred has enabled us to (1) establish a typology for classifying molar roots, (2) devise a methodology for evaluating the degree of taurodontism and (3) hypothesize about phylogenetic, ontogenetic and genetic aspects of root morphology. The roots of molar teeth were studied radiographically in 20 members of a family of English–German ancestry in which there was no consanguinity. Taurodont, pyramidal (single conical root) and fused molar roots were common. Other ectodermal and mesodermal anomalies (unusual upper lip, glaucoma, syndactyly and clinodactyly) were also present. This unique constellation of dental, cutaneous, ocular and bone abnormalities constitutes a previously undescribed syndrome. Unusual roots may be a genetic marker, and the finding of unusual roots, such as prismatic or wholly pyramidal, should prompt a search for other abnormalites. Dental trait analysis for genetic and microevolutionary studies should include root, as well as crown, characteristics.