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The formation and spread of the Australian arid zone during the Neogene was a profoundly transformative event in the biogeographic history of Australia, resulting in extinction or range contraction in lineages adapted to mesic habitats, as well as diversification and range expansion in arid-adapted taxa (most of which evolved from mesic ancestors). However, the geographic origins of the arid zone biota are still relatively poorly understood, especially among highly diverse invertebrate lineages, many of which are themselves poorly documented at the species level. Spiny trapdoor spiders (Idiopidae: Arbanitinae) are one such lineage, having mesic ‘on-the-continent’ Gondwanan origins, while also having experienced major arid zone radiations in select clades. In this study, we present new orthologous nuclear markers for the phylogenetic inference of mygalomorph spiders, and use them to infer the phylogeny of Australasian Idiopidae with a 12-gene parallel tagged amplicon next-generation sequencing approach. We use these data to test the mode and timing of diversification of arid-adapted idiopid lineages across mainland Australia, and employ a continent-wide sampling of the fauna’s phylogenetic and geographic diversity to facilitate ancestral area inference. We further explore the evolution of phenotypic and behavioural characters associated with both arid and mesic environments, and test an ‘out of south-western Australia’ hypothesis for the origin of arid zone clades. Three lineages of Idiopidae are shown to have diversified in the arid zone during the Miocene, one (genus Euoplos) exclusively in Western Australia. Arid zone Blakistonia likely had their origins in South Australia, whereas in the most widespread genus Aganippe, a more complex scenario is evident, with likely range expansion from southern Western Australia to southern South Australia, from where the bulk of the arid zone fauna then originated. In Aganippe, remarkable adaptations to phragmotic burrow-plugging in transitional arid zone taxa have evolved twice independently in Western Australia, while in Misgolas and Cataxia, burrow door-building behaviours have likely been independently lost at least three times in the eastern Australian mesic zone. We also show that the presence of idiopids in New Zealand (Cantuaria) is likely to be the result of recent dispersal from Australia, rather than ancient continental vicariance. By providing the first comprehensive, continental synopsis of arid zone biogeography in an Australian arachnid lineage, we show that the diversification of arbanitine Idiopidae was intimately associated with climate shifts during the Neogene, resulting in multiple Mio-Pliocene radiations.

This paper reports on species of the idiopid trapdoor spider genus Misgolas Karsch, 1878 found in the Illawarra and South Coast Regions of New South Wales, Australia. They comprise eight new species: M. horsemanae n.sp., M. gwennethae n.sp., M. phippsi n.sp., M. kampenae n.sp., M. paulaskewi n.sp., M. rowelli n.sp., M. tannerae n.sp. and M. shawi n.sp. Four species dealt with in Wishart (1992) and one in Wishart (2006) are also included in the region covered by this work: M. rapax (synonymous with M. hubbardi), M. dereki, M. kirstiae, M. robertsi (Main & Mascord, 1974) and M. gracilis respectively. M. elegans (Rainbow & Pulleine, 1918) is retained here but is regarded as a nomen dubium. Evidence is provided supporting the species status of M. montanus (Rainbow & Pulleine, 1918). A key for males of the species within the region is presented, as well as distribution map and comments on taxonomy and natural history.

This paper reports on species of the idiopid trapdoor spider genus Misgolas Karsch, 1878 found in the Central Coast, Newcastle and Lower Mid-North Coast Regions of New South Wales, Australia. They comprise twenty-two new species: M. mudfordae n.sp., M. thompsonae n.sp., M. tarnawskiae n.sp., M. dougweiri n.sp., M. maxhicksi n.sp., M. campbelli n.sp., M. yorkmainae n.sp., M. helensmithae n.sp., M. weigelorum n.sp., M. taiti n.sp., M. sydjordanae n.sp., M. davidwilsoni n.sp., M. crawfordorum n.sp., M. watsonorum n.sp., M. raveni n.sp., M. fredcoylei n.sp., M. billsheari n.sp., M. baehrae n.sp., M. macei n.sp., M. grayi n.sp., M. browningi n.sp. and M. linklateri n.sp. Three species dealt with in Wishart (2006) are also included in the region covered by this work: M. melancholicus, M. villosus and M. gracilis. A key for males of the species within the regions is presented, as well as distribution maps and comments on taxonomy and natural history. Also included is one new species from Bondi, an eastern suburb of Sydney—M. milledgei. The status of the Misgolas species dealt with by Wishart (2006) is clarified. An outline of the intervention of molecular work necessitated by need to match otherwise undiagnosable species with conspecific males is discussed. Misgolas hubbardi is placed in the synonymy of M. rapax as it shows no significant morphological differences in the females of the two species, nor significant molecular divergence. Dyarcyops ionthus, Arbanitis montanus and A. chisholmi are removed from the synonymy of M. rapax; and A. fuscipes is removed from the synonymy of M. villosus. A. montanus is given full species status. Dyarcyops ionthus, A. chisholmi and A. fuscipes are species incertae sedis.

This paper reports on the species of the Idiopid trapdoor spider genus Misgolas Karsch, 1878 found in the Sydney Region of New South Wales, Australia. They comprise seven new species: M. lynabra n.sp., M. cliffi n.sp., M. trangae n.sp., M. wayorum n.sp., M. rodi n.sp., M. beni n.sp. and M. michaeli n.sp.; and four species which are rediagnosed or redescribed here: Arbanitis gracilis, Dyarcyops maculosus, D. melancholicus and Megalosara villosa. The latter two species, plus Arbanitis fuscipes, Dyarcyops ionthus, Dyarcyops montanus and Arbanitis chisholmi are removed from synonymy with M. rapax. Their current or revised status is listed. This latter species, popularly known as the Sydney Brown Trapdoor Spider, is shown not to occur in the Sydney Region. A key for males of species within the region is presented, as well as distribution maps and comments on taxonomy and natural history.

The family Ctenizidae is redefined and the Australian genera, for the present, are allocated to the subfamilies Ctenizinae and Homogoninae and to the tribes Pachylomerini, Aganippini, Cataxini, Arbanitini and Homogonini. Of the twenty-one nominal genera, ten are accepted here as valid genera within the Ctenizidae and one new genus, Neohomogona, is described. All accepted genera and the typespecies of newly synonymized genera are diagnosed. The new species Neohomogona bolganupensis, N. stirlingi and Cataxia dietrichae are described. The validity of Arbanitis Koch is justified in order to maintain nomenclatural stability. The genera Evoplos Rainbow, Albanians Rainbow & Pulleine, Bancroftiana Rainbow & Pulleine and Armadalia Rainbow & Pulleine are newly synonymized with Arbanitis, and Cantuaria Hogg is again sunk in Arbanitis. Hermeas Karsch, Dyarcyops Hogg and Megalosara Rainbow are newly synonymized with Misgolas Karsch, and Cantuarides Strand is newly synonymized with Blakistonia Hogg. All nominal Australian species attributed to the Ctenizidae are allocated to genera as here diagnosed or removed to other families; several species originally placed in other families are transferred to the Ctenizidae. Of the eleven genera occurring in Australia, eight are endemic (Aganippe Cambridge, Idiosoma Ausserer, Eucyrtops Pocock, Anidiops Pocock, Cataxia Rainbow, Blakistonia Hogg, Homogona Rainbow, and Neohomogona, gen, nov.), two share a geographic range with New Zealand (Arbanitis and Misgolas), and one, Conothele Thorell, ranges through southeast Asia and New Guinea into Australia. The distribution of genera within Australia and their natural history are briefly discussed.