The Butterfly telescope goldfish (Teichfischer, 1994) is a variant of telescope goldfish that is distinguished by the butterfly-shaped caudal fins when viewed from above.
[1] It is a variety that has only recently been deemed a major lineage by a few published works.
The tail conformation is commonly bred into the telescope eye goldfish, the term "butterfly tail" is just short for the many names this variety has such as Butterfly Tail Demekin, Butterfly Tail Black Moor and Top view Telescope (TVT), and many other goldfish varieties.
The butterfly telescope goldfish is a variant form of the telescope goldfish with protruding eyes and is best appreciated by viewing it from above.
While this tail variation is commonly paired with the telescope eye variation, 'butterfly shaped tails' may be present in other goldfish standard varieties such as ryukins or orandas.