Small snails in a big place: a radiation in the semi-arid rangelands in northern Australia (Eupulmonata, Camaenidae, Nanotrachia gen. nov.) Author Köhler, Frank Author Criscione, Francesco text Zoological Journal of the Linnean Society 2013 Zool. J. Linn. Soc. 2013-08-29 169 1 103 123 http://dx.doi.org/10.1111/zoj.12051 journal article 10.1111/zoj.12051 0024-4082 4890431 281CB6ED-063E-4CF0-89A2-80EB3761BCDB NANOTRACHIA GEN. NOV. Type species: Ordtrachia intermedia Solem, 1984 . Description Shell ( Figs 4 , 5 ): Relatively small, flat, thin to moderately thick; periphery rounded to strongly keeled; spire moderately to weakly elevated; umbilicus open, wide, rarely partly concealed by columellar reflection; protoconch and teleoconch with dense, pointed periostracal projections and fine axial growth lines; teleoconch with or without axial ribs; last whorl moderately wide in cross section; apertural lip reflected, moderately expanded, without lip nodes; parietal wall thin; colour uniform, horn to brown. Genitalia ( Figs 6 , 7 ): Spermoviduct, lacking diverticulum and stimulatory organs. Penial sheath well-developed, extending entire length of penis, membranous. Penial retractor muscle inserting on vas–epiphallic junction; in some species muscular fibres extending onto penial apex. Epiphallus well developed; wall comprising thick layers of muscle; connected to penis through simple duct and pore; length equivalent to 20–100% of penis. Vas deferens entering penial sheath basally to halfway up, before reflexing into epiphallus. Penis thin with thin wall; not coiled within penial sheath; inner penial wall with between one and three narrow to thick, straight or winding, longitudinal pilasters, in some species with regularly spaced, pointed corrugations. Vaginal length equivalent to 50–100% of penis, twice as long as free oviduct. Bursa copulatrix simple, distally slightly inflated, comparatively short, extending to, or nearly to, anterior end of spermoviduct. Comparative remarks Shell easily distinguished from other camaenid genera from the VRD and EK by its small size, flat shape, open umbilicus, microscopic pustulation. Differing from Cristilabrum Solem, 1981 , Exiligada , Mesodontrachia , Ningbingia Solem, 1981 , Nodulabium Criscione & Köhler, 2013 , Ototrachia Criscione & Köhler, 2013 , Prototrachia Solem, 1984 , Pseudomesodontrachia Criscione & Köhler, 2013 , Turgenitubulus Solem, 1981 , and Vincentrachia Criscione & penis. Muscle fibres connecting median portion of epiphallus to penial apex. Vas deferens entering penial sheath halfway up. Inner penial wall with a single, wide, long, irregularly S-shaped pilaster, comprising apical two-thirds of wall. Vagina about as long as penis, from half to twice as long as free oviduct. Comparative remarks Shell similar to N. costulata sp. nov. , differing from N. carinata sp. nov. , N. coronata sp. nov. , and N. orientalis by less developed peripheral keel, and from N. levis sp. nov. by presence of axial ribs. Genital anatomy differing from N. carinata sp. nov. , N. coronata sp. nov. , and N. levis sp. nov. by smooth penial wall pilasters and long epiphallus; differing from N. costulata sp. nov. by fewer number of pilasters (one instead of three). Figure 7. Intraspecific variation of penial anatomy in N. costulata sp. nov. A, Nanotrachia c. costulata (holotype WAM S66302); B, Nanotrachia c. costulata (WAM S49174 ); C, Nanotrachia c. montejinni ssp. nov. (holotype NTM P48939); D, Nanotrachia c. montejinni (AM C.437659). Insets showing schematic cross section of midpenis. Scale bar = 2 mm. Köhler, 2013 by smaller and less conical shape. Differing from most Ordtrachia species by smaller size and presence of axial ribs, and from O. elegans by stronger axial sculpture and periostracal projections. Differing from M. occidentalis ( Fig. 4G ) by callus not detached from parietal wall.