The genus
Entosiphon was described by
Friedrich Stein in 1878. It was established to transfer a species of
Anisonema,
A. sulcata, to a separate genus, which changed the original spelling of this species to
E. sulcatum. A second species,
E. oblongum, was described in 2016. The evolutionary position of
Entosiphon among euglenids is unstable, either branching with
Hemiolia and
Liburna or forming a separate branch, depending on the methods and datasets used. In all cases, it consistently branches among basal, non-flexible euglenids, outside of any major euglenid group. ==References==