The unmistakable members of the melanopus group reveal some intriguing biogeographic patterns and the likely presence of numerous cryptic species. These fishes are sometimes referred to together as the Tomato Anemonefishes, though this name also refers more specifically to the most well-known member of this lineage, A. frenatus.
The most obvious distinction of this group is the absence of the posterior two stripes (a feature shared with the very different A. nigripes and A. mccullochi). These stripes are, however, present in juveniles but are lost with age. Also of note is the relatively blunt, bulky shape these fishes possess.
While many of the currently recognized taxa are easily separated, there is reason to believe that certain populations currently treated as a single widespread species, A. melanopus, are actually distinct enough to warrant species recognition. Not all of these are easily identified beyond their biogeography, but genetic and meristic data will likely reveal their true affinities.
Ecologically, the melanopus group has specialized in hosting within the colonial form of the Bubbletip Anemone (Entacmaea quadricolor) and can often be found in enormous colonies formed from hundreds of anemones and dozens of anemonefishes. Little is known about how these aggressive, territorial fish behave among one another in such cramped quarters.