The main hypothesis of this work is that the family Hexathelidae is a distinct monophyletic unit separate from the Dipluridae and that the biogeography of both families within Australia and in the rest of the world supports that hypothesis.
The subfamily Hexathelinae is revised and four new genera and thirteen new species are described. Application of Hennigian phylogenetic systematics to the Dipluridae, s. lat. has revealed that the Hexathelinae are paraphyletic and that the sister group of five of the genera (Bymainiella, Terania, Paraembolides, Hexathele and Scotinoecus) is the Macrothelinae, redefined to include only Macrothele, Porrhothele and Atrax; the Plesiothelinae, including only the monotypic genus Plesiothele, are the sister group of both the Macrothelinae and the Hexathelinae. All three subfamilies constitute the newly elevated Hexathelidae.
The Australian diplurine genera are reviewed and Chenistonia, Dekana, Sungenia and Dolichosternum are synonymized with Aname. The previously confused concepts of Aname and Ixamatus are clarified. Ixamatus is revised and now includes eight species, six of which are new, and a new genus, Xamiatus, of five new species is described.
A new species of Masteria, a genus previously unknown in Australia, is described and the tribe, Masteriae, is given subfamily rank. The affinities of the Masteriinae are with the Evagrini, a newly elevated tribe in the Ischnothelinae. That subfamily name is restored because the name Macrothelinae is no longer available for the diplurid genera previously included in that subfamily. The Australian Evagrini are revised. Eight new species of Cethegus Thorell, and three new genera including thirteen new species, are described. A synonymized genus, Stenygrocercus, is restored and in it a new species, S. australiensis, the only Australian species in an otherwise New Caledonian genus,is included. The type - species of each of the poorly known genera, Phyxioschaema and Stenygrocercus are described, and into the latter a new species, S. annulata, from New Caledonia, is placed. The Ischnothelinae are shown to be diphyletic and the Ischnothelini are concluded to be the most plesiomorphic group within the Dipluridae. The monophyly of the Dipluridae is doubtful.
The phylogeny of many of the groups mentioned is discussed and, although in some characters the case for their synapomorphv is weak, the zoogeographic hypotheses constructed from the cladograms of different genera show general correspondence. Within the Australian region, the two major events influencing hexathelid and diplurid distributions were the uplift of the Great Dividing Range and the northward drift of Australia through decreasing latitudes and the ecological changes associated with those two events.