We identified a total of 286 IFITM-related sequences ( Table 1 ). The number of IFITM genes varies considerably between mammals and non-mammalian vertebrates. A total of 27 functional genes were identified from 10 non-mammalian species, ranging from one gene in stickleback or tetraodon to six genes in frog. By contrast, 134 functional genes were identified from 17 mammalian species, ranging from one in platypus or rabbit to 26 in marmoset. Additionally, 14 putative functional genes including 13 in mammals and one in non-mammalian vertebrates were identified. Among the 10 non-mammalian and 17 mammalian species, 10 and 102 pseudogenes were identified, respectively. Interestingly, among 10 non-mammalian vertebrates, frog has the highest number (six functional genes and eight pseudogenes) of IFITM-related sequences. Among the 17 mammals, marmoset has the highest number (40) of IFITM-related sequences, of which 26 are functional genes. Human has the second highest number (29) of IFITM-related sequences, of which 18 are pseudogenes, the maximum in vertebrates.