Fastosarion alyssa (Stanisic, 2010) Figs. 14D, 18, 19A, 10A–D, 21, 22A–B Dimidarion alyssa Stanisic, 2010 in Stanisic et al., 2010: 314–315, 332. Dimidarion peterbrocki Stanisic, 2010 in Stanisic et al., 2010: 316–317, 333. Dimidarion slatyeri Stanisic, 2010 in Stanisic et al., 2010: 316–317, 333. Material examined Types: Holotype of D. alyssa: QM MO 43387 (Johannsens Caves, Fitzroy Caves NP, MEQ, 23°09’S, 150°27’E, sevt/limestone outcrop, under rocks and logs, 4 July 1984, J. Stanisic, D. Potter, K. Emberton). Paratypes of D. alyssa: QM MO 21610, QM MO34264, QM MO62566, QM MO62569, QM MO62571, QM MO62572, QM MO78900, AMSC425279, AMSC425281, AMSC425282. Holotype of D. peterbrocki: QM MO 19923 (4.5 km along Brandy Ck Rd, Conway SF, MEQ, 22°40’15” S, 148°00’55” E, 15 June 1987, J. Stanisic, D. Potter). Paratypes of D. peterbrocki: QM MO 11678, QM MO11697, QM MO35541, QM MO54769, QM MO60707, QM MO78899, AMSC425256, AMSC425257, AMSC425259. Holotype of D. slatyeri: QM MO 78022 (Peak Range, via Clermont, SE slope Lords Table Mtn, MEQ, 22°40’15” S, 148°05’00” E, vine thicket, under rocks, 9.i.2006, J. Stanisic, T. Carless). Paratypes of D. slatyeri: QM MO 78898. Diagnosis External morphology: Shell (figs. 14D, 19A) small (7.5–9.8 mm), pale golden amber, transparent, 2.9–3.1 whorls, flattened, thin, last whorl large. Body (fig. 10A–D) 18–28 mm, speckled cream to brown, darker along sides of tail; shell lappets and mantle lobes moderately large, right lappet rounded, with horizontal dark brown ridge near lower edge; black line along mantle edge. Tail not keeled, slime network prominent. Internal organs show clearly through transparent shell: yellow-coloured kidney fills most of last whorl; curved orange-brown finger of digestive gland lies on first half of last whorl. Genital anatomy: Genitalia (figs. 21, 22A–B) with short vagina; bursa copulatrix moderately short, duct distinct, bursa spherical to oval. Penis long, swollen proximally, internally with 1–3 minor longitudinal pilasters and one large rounded pilaster proximally; internal wall smooth or pustulose; 75–90% of penis contained in penial tunica. Epiphallus approx. 1.5 times length of penis; epiphallic caecum long, usually lying alongside epiphallus 1; flagellum short, slender. Spermatophore simple, with a small spiraling row of teeth at tail tip. Remarks Dimidarion was introduced for four species, newly described on the basis of slight differences in their external morphology: D. alyssa, D. slatyeri, D. peterbrocki and D. minerva. The fourth species (minerva) is anatomically distinct from the others and is addressed further below. The first three species were originally distinguished from one another by slight differences in size and body colour as well as geographical separation (Stanisic et al., 2010). Material from the type localities of all three species was included in the current study, as well as material of additional candidate species Helicarionidae BL 1, MQ17, MQ10 and MQ12 identified through curatorial work. Most locations were represented by 2- 3 specimens and most formed monophyletic clusters (e.g., Dan Dan NP, Mt Etna Caves, Peak Range, Blue Mountain NP, Marlborough), but the differences between them were very slight. Dissections showed correspondingly very slight anatomical differences. We consider these differences to be consistent with intraspecific variation between relatively isolated populations and hereby synonymise the three names. One population was genetically more divergent and showed clear anatomical differences; this is described below as separate species F. insularis. The range of F. alyssa as so delimited stretches from the Caves north of Rockhampton in southeastern Qld to Bowen in mideastern Qld (fig. 18). The species is found in dry vine thickets, often on limestone outcrops, living under logs, rocks and leaf litter. It co-occurs with several of its congeners, including F. papillosus, F. longimentula, F. sarina, F. superbus, F. aquavitae and F. griseolus, but can be distinguished from these species by its smaller body and more flattened shell.

Published as part of Hyman, Isabel T. & Köhler, Frank, 2019, Phylogeny and systematic revision of the helicarionid semislugs of eastern Queensland (Stylommatophora, Helicarionidae), pp. 351-451 in Contributions to Zoology 88 (4) on pages 415-416, DOI: 10.1163/18759866-20191416, http://zenodo.org/record/8343061