Four new species of the whalefish genus Gyrinomimus Parr, 1934, with the establishment of three new species groups (Beryciformes, Cetomimidae).

Four new species of the flabby whalefish genus Gyrinomimus Parr, 1934 are described based on female specimens: G. alepis sp. nov. from the southern Atlantic, G. amaokai sp. nov. from the Northern Hemisphere, G. johnpaxtoni Su & Ho, sp. nov. from the Pacific and Atlantic, and G. johnsoni sp. nov. from the northern Pacific. Each of the new species differs from congeners in the length of gill filaments on fourth gill arch, numbers of dorsal- and anal-fin rays, gill rakers, head and lateral-line pores, anal lappets and vertebrae, distribution of cavernous tissue, and the shape and length/width ratio of copular tooth plate. Moreover, three species groups are defined: G. bruuni species group, G. grahami species group, and G. myersi species group. Each group differs in the length of gill filaments, numbers of anal lappet and gill rakers, and distribution of cavernous tissue. Diagnostic characters and detailed descriptions of the new species are provided and compared to congeners, with variations discussed. Finally, an identification key to species groups and all known species is provided.