Cunningham described this species in Irpex Fr. mainly because the pore mouths in mature specimens are partly split. However, this macroscopic feature is now considered to be of minor importance in delimiting genera. Many genera, such as Antrodia P. Karst., Trametes Fr., and Spongipellis Pat., include some species with a regular pore surface and others with a more or less dentate one. Irpex is typified by I. lacteus Fr. (see Maas Geesteranus, 1974), a distinctly hydnoid species with a dimitic hyphal system. The generative hyphae are simple septate and the cystidia develop from protruding skeletal hyphae which are encrusted over a considerable length. The cystidia in O. spiculifer are typically ventricose and apically encrusted, although some hyphae in the dissepiments are encrusted over longer segments. The cystidia and monomitic hyphal system of O. spiculifer indicate that it does not belong in Irpex.
Oxyporus Donk is characterised by a monomitic hyphal system with simple septate generative hyphae and mostly apically encrusted cystidia. O. pellicula (Jungh.) Ryv. from tropical Africa and Asia is similar in many respects to O. spiculifer, with a dentate, lacerate pore surface, but its spores are larger and more broadly ellipsoid. Spores of O. spiculifer measure 5-6.5 x 2.5-3 µm, larger than the dimensions given by Cunningham (1965) of 4-5 x 1.5-2 µm. From herbarium material, the type of rot appears to be white.

Holotype: PDD 19144 - New Zealand, Buller, vic. Reefton, Staircase Creek, 29 Nov. 1952, S.D. Baker, on Nothofagus fusca (Hook. f.) Oerst.