Chronogram showing divergence dates for selected mammalian species. Branches are shown in gray for relatively hairless lineages  and in black for taxa with greater hair cover. Lineages that are completely aquatic are italicized. An asterisk indicates domestic species for which mutations in the FGF5 gene have been identified as responsible for long hair phenotypes in one or more breeds [2, 5, 6, 8]. The relationships depicted among taxa, and the divergence dates on the chronogram, are from previously published paleontological [30, 31] or genetic [9, 10, 34, 39] studies.