[4] They have also been observed feeding on gelatinous zooplankton, such as jellyfish (Scyphozoa) and comb jellies (Ctenophora).

[5] The diagonal butterflyfish was first formally described in 1775 by the Swedish speaking Finnish born naturalist Peter Forsskål (1732-1763) with the type locality given as Jeddah.

In this group, its closest relative is probably the very similar common raccoon butterflyfish (C. lunula).

Although the coloration of this group varies quite a lot, they are all largish butterflyfishes with an oval outline, and most have a pattern of ascending oblique stripes on the flanks.

Except in the red-tailed butterflyfish, there is at least a vestigial form of the "raccoon" mask, with a white space between the dark crown and eye areas.