The world’s most specialised cave-dwelling trapdoor spider, Troglodiplura, is known only from the caves in Australia’s Nullarbor Plain. Although it was previously thought to be most closely related to South American spiders, we use sequence data to show that Troglodiplura belongs to the Australian endemic family Anamidae. In addition to the originally described species, T. lowryi, we found four new species. Each of the five species are restricted to individual caves, and are likely under threat from changing environmental conditions within the caves.

Comprehensive taxonomic review is required to fully characterise Amphioctopus ovulum because the syntypes are missing and the description is insufficiently complete for modern octopod taxonomy. In this study, the species is redescribed with morphological and morphometric characters of 18 specimens collected from the coastal waters of China. Amphioctopus ovulum was clearly differentiated from two other similar violet-ringed octopuses by comparative morphological analyses and phylogenetic analysis based on COI and COIII genes. Additional morphological and molecular data would help to identify these similar octopods and resolve higher-level phylogenetic relationships within the Octopodidae.

Australian waters harbour remarkably diverse assemblages of sea spiders (Pycnogonida), including the endemic genus Pallenella Schimkewitsch, 1909 with several colourful but morphologically similar forms. Using an integrative taxonomic approach, we studied the extraordinary diversity of Pallenella in south-east Tasmania. Based on concordance of morphology, live colouration and two molecular markers, we distinguish 13 congeners and describe two new species. To date, this represents the most diverse assemblage of sympatric species in the same microhabitat reported for a single pycnogonid genus.

Sexually dimorphic glands are widespread in the legs of armoured harvestmen (Arachnida, Opiliones, Laniatores), but it remains unclear in which cases these glands are homologous. Using the family Zalmoxidae as a model, we first describe four new species of Palaeotropical Zalmoxis, including a species with sexually dimorphic glands. Next, we analyse the morphology of glands in different species, and, using a molecular phylogeny of the family, provide evidence that very similar sexually dimorphic leg glands evolved independently in species on both sides of the Pacific.

Despite recent efforts to better understand the diversity and relationships in the orb-weaving spider family Araneidae, many taxa remain unplaced. We place Nemoscolus, a taxon notable for its retreat constructed of pebbles, in the araneid tree of life, in the subfamily including argiopines. This suggests another novel evolution of retreats in araneoid webs as well as a foundation for better understanding other members of this little-known genus.