A revision of eastern Australian land snails placed in Nitor Gude (Helicarionidae, Stylommatophora) Isabel T. Hyman A,B and Frank Köhler A A Australian Museum, 1 William St, Sydney, NSW 2010, Australia. B Corresponding author. Email: Isabel.Hyman@austmus.gov.au Abstract. Nitor Gude, 1911 is a genus of helicarionid land snails currently comprising eight species ranging from southern New South Wales to northern Queensland. We comprehensively revise the taxonomy of this group based on comparative morphology and on mitochondrial genes cytochrome c oxidase subunit I and 16S rRNA, provide a new generic diagnosis, revise species descriptions and describe four new species. Two species, ‘N.’ reisi Stanisic, 2010 from northern Queensland and ‘N.’ whitneyae Stnaisic, 2010 from mid-eastern Queensland, are removed from Nitor. Revised species descriptions are given for N. subrugatus (Reeve, 1852), N. medioximus Iredale, 1941, N. circumcinctus (Cox, 1868), N. wiangariensis Hyman, 2007 and N. pudibundus (Cox, 1868); N. helmsianus Iredale, 1941 (previously considered a synonym of N. subrugatus) is reinstated; and new species N. glenugie, N. sheai, N. benjamini and N. pipinna are described. Helix graftonensis Cox, 1864 is synonymised with N. subrugatus. We demonstrate that Nitor is closely related to Lord Howe Island taxa Epiglypta Pilsbry, 1893, Gudeoconcha Iredale, 1944, Howearion Iredale, 1944 and Parmellops Iredale, 1944; the five genera are united by a combination of characters including the presence of a distinct vagina, a slender epiphallic flagellum forming a simple spermatophore and an epiphallic caecum with terminal attachment of the penial retractor muscle. Additional keywords: comparative morphology, mitochondrial DNA, systematics, taxonomy. Received 23 February 2018, accepted 17 May 2018, published online 15 October 2018 Introduction The Helicarionidae is a family of snails and semislugs found throughout Australia, some islands of the Pacific, south-eastern Asia, Madagascar and the Mascarene Islands. Primarily rainforest dwellers, most of the ~100 described Australian helicarionid species occur along the east coast east of the Great Dividing Range (Stanisic et al. 2010). To date, more than half of these species are known only by their shell morphology, including 47 recently described species (Stanisic et al. 2010). Hence, it is no surprise that the systematic classification of the Australian Helicarionidae is still predominantly based on shell characters (e.g. Smith et al. 2002; Stanisic et al. 2010). Many anatomical studies have been based on single taxa (Dartnall and Kershaw 1978; Kershaw 1979, 1981; Solem 1982, 1988; Stanisic 1993a, 1993b, 1998; Scott 1995). A series of papers by Hyman and co-authors included anatomical descriptions of 34 Australian species and subspecies in 22 genera, as well as mitochondrial gene sequences of 15 species (Hyman 2007; Hyman et al. 2007; Hyman and Ponder 2010, 2016), but this was still insufficient to resolve the relationships in this complex group. More recently, Hyman et al.(2017) and Hyman and Köhler (2018a, 2018b) comprehensively revised nine helicarionid genera from south-eastern Australia using comparative morphology and molecular phylogenetics. The generic relationships still could not fully be resolved; however, these detailed revisions provide an important insight into the taxonomically significant characters and into inter- and intraspecific variation, setting a standard for the delimitation of species boundaries in Australian Helicarionidae. The genus Nitor Gude, 1911, as currently understood, ranges from southern NSW to northern Qld containing eight mostly allopatric or parapatric species that are essentially distinguished by shell characteristics (Stanisic et al. 2010). Nitor circumcinctus (Cox, 1868) is the southernmost species, ranging from Deua National Park (NP) to the Hunter Region in southern NSW. Further north, Nitor medioximus Iredale, 1941 and Nitor graftonensis (Cox, 1864) have been reported from the Clarence River catchment in north-eastern NSW. The type species of the genus, Nitor subrugatus (Reeve, 1852), is sympatric with Nitor wiangariensis Hyman, 2007 and Nitor pudibundus Cox, 1868) around the NSW–Qld border region. Two recently described species, Nitor whitneyae Stanisic, 2010 and Nitor reisi Stanisic, 2010, occur much further north in mid-eastern and north-eastern Qld, respectively (Stanisic et al. 2010). Among other Australian helicarionids, the group is characterised by the small to medium-sized, thin, depressedly trochoidal shell with a Journal compilation Ó CSIRO 2018 www.publish.csiro.au/journals/is CSIRO PUBLISHING Invertebrate Systematics, 2018, 32, 1171–1205 https://doi.org/10.1071/IS18015