Review of the Papuan millipede genus Acanthiulus Gervais, 1844 (Diplopoda: Spirobolida: Pachybolidae)

Abstract

The genus Acanthiulus, which has hitherto been known to comprise three accepted species or subspecies endemic to the Papuan region, is revised, rediagnosed and shown to include only a single, quite variable species, A. blainvillei (Leguillou, 1841), with A. blainvillei septemtrionalis Attems, 1914 and A. wollastoni Hirst, 1914 both considered as its new subjective junior synonyms, syn. nov. Pronounced morphological variations, all clearly illustrated here, concern only peripheral characters, but the gonopodal structure remains very stable. Three morphs are distinguished: A, B and C. The distribution of A. blainvillei is mapped, the genus and species apparently being restricted to the Aru Archipelago, East Indonesia and much of New Guinea, both Indonesian and Papua New Guinea. Certain clinal variation patterns and an evolutionary scenario can be suggested in the distribution and polymorphism of the widespread species A. blainvillei at the northern periphery and in the centre of its distribution area.