A new species of sponge-inhabiting barnacle, Membranobalanus porphyrophilus sp. nov., is described herein. This species can be distinguished from all other congeners by a combination of characters, in particular by the shapes of the tergum and scutum and the armament of the cirri. COI sequence data from the type specimens have been lodged with GenBank and a morphological key to the species of Membranobalanus is provided to aid future research. The host of the new species is the southern Australian endemic demosponge Spheciospongia purpurea. The new species of barnacle is thought to be host species specific.
Keywords: Archaeobalanidae; Clionaidae; Demospongiae; Spheciospongia purpurea; bioeroder; commensal; computed tomography; specificity; symbiosis; temperate reef..