The genus Ericthonius has undergone much revision (see Myers & McGrath 1984). Lowry & Berents (1996) considered Ericthonius and Pseudoericthonius to be paraphyletic taxa in a cladistic analysis of the ‘ Ericthonius ’ group, which established the Cerapus and Siphonoecetes clades as sister taxa. Myers & Lowry (2003) analysed Ericthonius as part of a much larger corophiidean phylogeny and placed the ‘ Ericthonius ’ group in the Photoidea: Ischyroceriidae: Ischyroceriinae: Siphonoecetini.
In a review of the NorthEast Atlantic Ericthonius species Myers & McGrath (1984) divided the genus into two groups. The two new Australian species are part of ‘group one’ in which the gnathopod 2 coxa has stridulating ridges, coxa 2 is widely separated from coxa 1 and 3, and gnathopod 2 carpus has two teeth or one in some hyperadults. The six Australian species of Ericthonius can be divided based on the gnathopod 2 basis, broad in E. brevicarpus Vader & Myers, 1996, E. coxacanthus Moore, 1988 and E. tacticus Moore, 1988 and thin and elongate in E. forbesii sp. nov., E. pugnax Dana, 1852 and E. rodneyi sp. nov.