The effect of Tbx15 on pigmentation in laboratory mice is reminiscent of coat-color patterns in both selected and natural populations of other mammals. Saddle markings are common in some dog breeds, such as German shepherds, and in certain populations of Peromyscus polionotus, in which a dorsal extension of ventral depigmentation provides an adaptive advantage to subspecies that live on white sand reefs (Blair 1951; Kaufman 1974; Belk and Smith 1996). Neither German shepherds nor deer mice have craniofacial characteristics similar to the deH mutation, but the pigmentation patterns in these animals could represent alterations in the regulation or action of Tbx15 activity. From the opposite perspective, the effects of Tbx15 on coat color are only apparent in certain genetic backgrounds and may not be evident at all in mammals that lack dorsoventral pigmentation patterns. Studying the sequence and expression of Tbx15 in other vertebrates may provide additional insight into patterns that affect the skeleton as well as the pigmentary system.