Flabby whalefishes are small, deep-sea cetomimiform fish of the family Cetomimidae. They are among the most deep-living fish known, with some species recorded at depths in excess of 3.5 kilometres. Within the family are nine genera and 20 species. Juveniles are known as tapetails and were formerly thought to be in a separate family, dubbed Mirapinnidae. Adults exhibit extreme sexual dimorphism, and the adult males were once thought to be exemplars of still another family, Megalomycteridae.
Thought to have a circumglobal distribution throughout the Southern Hemisphere, flabby whalefish are the most diverse family of whalefishes. The largest species, Gyrinomimus grahami, reaches a length of some 40 centimetres. They are distinguished from other whalefishes by their loose, scaleless skin and lack of photophores.
Comparison chart of the larva, male and the female of the Flabby Whalefish.