The secondary hair loss in cetacean species was suggested as an evolutionary innovation to adapt completely aquatic environment,yet its genetic basis remained poorly explored.We scanned KRTAP genes,one major structural components of hair,in six genomes of representative cetacean lineages and five genomes of artiodactyla species.It was revealed that extensive gene loss and high pseudogenization rate were identified in cetaceans when compared to terrestrial relatives(average number of KRTAP in cetaceans vs.artiodactylans: 51.7 vs.