Richmondaropa conjuncta (Iredale, 1941) Shea & Colgan & Stanisic, 2012

Shea, M., Colgan, D. J. & Stanisic, J., 2012, 3585, Zootaxa 3585, pp. 1-109 : 83-84

Richmondaropa conjuncta (Iredale, 1941) n. comb.

( Figs 30D, E; 32D, E; 34D, E; 36D, E; 38C, D)

Roblinella conjuncta Iredale, 1941b: 1 ; Iredale 1941a: 268 (illustration only).

Roblinella conjuncta: Smith 1992: 203 .

Gyrocochlea conjuncta (Iredale) : Stanisic et al. 2010: 200.

Type locality. Byron Bay , NSW .

Diagnosis. Shell very small, cinnamon brown, planispiral with flat to slightly depressed spire. Protoconch sculpture primarily spiral consisting of 17 prominent, widely spaced, narrow, continuous spiral cords; underlying weak radial ridges present. Teleoconch sculpture of numerous, prominent, quite uniformly spaced, slightly sinuate, orthocline to weakly prosocline radial ribs. Ribs on body whorl 67–100 (mean 77). Umbilicus wide U-shaped to cup-shaped.

Type material examined. Neotype (here designated) AM C.5311, Byron Bay , NSW (28° 39' S, 153° 37' E), 1908.

Other material examined. Byron Bay: AM C.140243, AM C.472888. Brunswick Heads: QMMO 16789.

Description. Shell very small, cinnamon-brown, planispiral with flat to slightly depressed spire. Whorls 3.50–4.25, tightly coiled, the last weakly expanding and strongly descending in front. Sutures strongly impressed. Shell diameter 3.46–4.04 mm (mean 3.74 mm), height 1.81–2.26 mm (mean 2.08 mm), H/D 0.50–0.59 (mean 0.55). Protoconch flat, of 1.12 whorls, diameter 0.56–0.67 mm. Protoconch sculpture primarily spiral consisting of 17 prominent, widely spaced, narrow, continuous spiral cords; underlying weak radial ridges present. Teleoconch sculpture of numerous, prominent, quite uniformly spaced, slightly sinuate, orthocline to weakly prosocline radial ribs. Ribs on body whorl 67–100 (mean 77), width of interstices on the first teleoconch whorl greater than or equal to width of six ribs; on the penultimate whorl greater than or equal to width of six ribs; each rib with one or more periostracal blades; with or without overlapping thickenings. 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 5–8; on first quarter of body whorl 13–17. Aperture broadly ovately-lunate. Parietal callus prominent, transparent. Umbilicus wide U-shaped to cup-shaped, diameter 0.80–1.16 mm (mean 0.99 mm), D/U 3.32–4.36 (mean 3.79). Based on 11 measured adults.

Anatomy unknown.

Distribution and habitat. Coastally in the Byron Bay region, north-eastern NSW; found in rainforest and vine thicket; living on underside of logs.

Remarks. Iredale (1941) did not provide details about the protoconch of the type of Richmondaropa conjuncta n. comb. when he described the species. The type cannot now be located so that the protoconch sculpture cannot be determined. However, by assigning the species to Roblinella Iredale, 1937 (type: Helix roblini Petterd, 1879 ) Iredale identified this species as having a primarily spiral protoconch (see note below). Additionally, the comparatively low rib count for the body whorl (approx. 80) given by Iredale (1941b) is distinctive among the nautiliform charopids of north-eastern NSW. The illustration of the species, provided by that author in a publication ( Iredale 1941a) preceding that in which the original description appeared ( Iredale 1941b), clearly shows the wide rib spacing on the body whorl. Contemporary collections from the coastal rainforests around the Byron Bay area have discovered specimens which align quite closely with Iredale’s description. Hence, in order to stabilise this name a neotype is here designated from this recently collected material.

R. conjuncta differs from R. prava by having more tightly coiled whorls and fewer, more widely spaced radial ribs on the teleoconch. This species may only be a regional variant of R. prava , however without DNA results and soft parts to study, full species status is retained pending further study. A second large undescribed planispiral charopid occurs sympatrically with R. conjuncta distinguished by more crowded teleoconch ribs, shallower whorls, wider umbilicus and a cancellate protoconch not dissimilar to ‘Gyrocochlea’ species. A specimen identified as R. conjuncta from the Byron Bay-Brunswick Heads road in the Queensland Museum collections had a higher teleoconch rib count (100), compared to other specimens from the Byron Bay area (up to 90). It is here included with R. conjuncta based on its proximity to the Byron Bay site but may in fact be R. prava .

Note. Four species from Tasmania ( H. agnewi Legrand, 1871 , H. curacoae Brazier, 1871 , H. mathinnae Petterd, 1879 , H. gadenensis Petterd, 1879 ), one from South Australia ( R. speranda Iredale, 1937 ) and Endodonta intermedia Odhner, 1917 from the Atherton Tableland, north-eastern Queensland, were originally placed in Roblinella by Iredale (1937) on the basis of spirally lirate protoconch sculpture. Subsequently, R. conjuncta Iredale, 1941 from Northern New South Wales was also assigned to this genus. Stanisic et al. (2010) reassigned R. intermedia to Sinployea Solem, 1983 . Here we have assigned R. conjuncta to Richmondaropa n. gen. Detailed examination of the micro-architecture of the protoconchs of the remaining Tasmanian representatives indicates that Roblinella still remains a polyphyletic taxon requiring revision (J. Stanisic unpublished data).