Type species. Maia lunulata Risso, 1816 [Type locality: Nice, France].
Remarks. Acanthonyx lunulatus (Risso, 1816) and A. petiverii H. Milne Edwards, 1834, are wide-ranging and morphologically variable and this may account for them having far more subjective junior synonyms than the other species in the genus. Tavares et al. (2017) recently clarified the status of A. brevifrons A. Milne-Edwards, 1869, recognized as a valid species based on molecular and morphological characters. Acanthonyx petiverii, along with all its junior synonym species, badly needs a taxonomic revision based on material from the various parts of its geographical range.