Kalmar "heterocercal fin" tana nufin wani nau'in wutsiya na kifi wanda babban lobe ya fi tsayi kuma ya fi girma fiye da ƙananan lobe, kuma ginshiƙan kashin baya ya shiga cikin lobe na sama. Wannan nau'in fin wutsiya shine halayyar kifin cartilaginous, kamar sharks da haskoki. Kalmar "heterocercal" ta samo asali ne daga kalmomin Helenanci "heteros," ma'anar "bambanta," da "kerkos," ma'ana "wutsiya."