Barbourisiidae Cetomimidae Rondeletiidae The Cetomimiformes or whalefishes are an order of small, deep-sea ray-finned fish.

Thought to have a circumglobal distribution throughout the tropical and temperate latitudes, whalefishes have been recorded at depths in excess of 3,500 metres.

Their eyes are very small or vestigial; the lateral line (composed of huge, hollow tubes) is consequently very well developed to compensate for life in the pitch black depths.

Sexual dimorphism is (apparently) exceptionally strong: males may only grow to 3.5 centimetres while females may be ten times as large.

The gibberfishes (Gibberichthyidae) on the other hand, usually placed in the Stephanoberyciformes sensu stricto, appear to be close relatives of the Rondeletiidae and Barbourisiidae, as has been occasionally proposed.