Planorbocochlea nambucca, Shea & Colgan & Stanisic, 2012

Shea, M., Colgan, D. J. & Stanisic, J., 2012, 3585, Zootaxa 3585, pp. 1-109 : 57-58

Planorbocochlea nambucca n. sp.

( Figs 20C; 21C; 22C; 23C; 24D; 25G; 26G)

Etymology. For Nambucca Heads.

Diagnosis. Shell very small, pale yellowish brown, biconcave with weakly depressed spire. Protoconch sculpture reticulate consisting of 14 to 15 prominent, widely spaced, beaded spiral cords and prominent, widely spaced radial ribs becoming more pronounced toward the protoconch-teleoconch boundary. Teleoconch sculpture of numerous, prominent, quite uniformly spaced, slightly sinuate, orthocline to opisthocline radial ribs. Ribs on body whorl 90–96. Penis with an expanded apical portion becoming tubular distally; several longitudinal pilasters present including one large thickened central V- or Y-shaped pilaster; verge absent.

Type material examined. Holotype. QMMO80159 , Nambucca Heads, rainforest reserve on slope S of town, NSW (30°38’ 05” S. 153° 00’ 00” E), 22.i.1993, coll. J. Stanisic, J. Chaseling. Paratypes. Nambucca Heads: QMMO44862 , QMMO49331 , AM C.139746, same data as holotype .

Description. Shell very small, pale yellowish brown, biconcave with weakly depressed spire. Whorls 3.87–4.00, tightly coiled, the last inflated and descending in front. Sutures weakly to strongly impressed. Shell diameter 3.25–3.27 mm (mean 3.26 mm), height 1.55–1.80 mm (mean 1.68 mm), H/D 0.48–0.55 (mean 0.51). Protoconch flat, of 1.12–1.25 whorls, diameter 0.44–0.51 mm. Protoconch sculpture reticulate consisting of 14 to 15 prominent, widely spaced, beaded spiral cords and prominent, widely spaced radial ribs becoming more pronounced toward the protoconch-teleoconch boundary. Teleoconch sculpture of numerous, prominent, quite uniformly spaced, slightly sinuate, orthocline to opisthocline radial ribs. Ribs on body whorl 90–96 (mean 94), width of interstices on the first teleoconch whorl equal to width of four or greater than or equal to width of six ribs; on the penultimate whorl equal to width of four to less than six ribs; each rib with single periostracal blade; overlapping thickenings absent. Interstitial sculpture of low prominent microradial ribs and low, weaker microspiral cords forming weak beads at their intersection; number of microradials between ribs on the first teleoconch whorl 8–11; on first quarter of body whorl 8–10. Aperture broadly ovately-lunate. Parietal callus prominent, transparent. Umbilicus wide U-shaped, diameter 0.92–0.96 mm (mean 0.94 mm), D/U 3.43–3.58 (mean 3.50). Based on 3 measured adults.

Reproductive tract with ovotestis containing two clumps of alveoli, with more than two alveolar lobes per clump. Hermaphroditic duct narrow to broad crescent-shaped. Spermatheca with a large oval bulb. Penial retractor muscle inserting at the junction of the penis and epiphallus. Epiphallus shorter or equal in length to the penis, entering penis through a simple pore (verge absent). Penis with an expanded apical portion becoming tubular distally; several longitudinal pilasters present including one large thickened central V- or Y-shaped pilaster. Vagina shorter than penis. Atrium short.

Distribution and habitat. Presently known only from the vicinity of Nambucca Heads, NSW; found in mixed rainforest/eucalypt forest association, living under logs.

Remarks. Conchologically Planorbacochlea nambucca n. sp. differs from the geographically proximate P. yessabahensis in having fewer spirals on the protoconch, a greater number of teleoconch ribs and a wider umbilicus. Anatomically it differs most significantly from other Planorbacochlea except P. reticulata by lacking a penial verge. This is a major departure from the typical generic pattern which when combined with the reticulate sculpture (lattice-like) comprising few spiral cords suggests lineage differentiation.

Material here described as a new species was included in G. wauchope Stanisic, 2010 (type locality Mt Seaview, NSW) by Stanisic et al. (2010). A number of additional species related to P. nambucca from the area between O’Sullivans Gap and Coffs Harbour, NSW are still to be described (Stanisic, unpublished data).