Planorbacochlea dandahra, Shea & Colgan & Stanisic, 2012

Shea, M., Colgan, D. J. & Stanisic, J., 2012, 3585, Zootaxa 3585, pp. 1-109 : 59-60

Planorbacochlea dandahra n. sp.

( Figs 20D; 21D; 22D; 23D)

Etymology. For the Dandahra Creek which flows through the Gibraltar Range National Park.

Diagnosis. Shell very small, pale pinkish brown, biconcave with depressed spire. Protoconch sculpture broadly reticulate consisting of 18 prominent, widely spaced, broad, continuous spiral cords that intersect with widely spaced radial ridges on the early part of the protoconch forming a lattice; the ridges developing into widely spaced radial ribs on the latter part of the protoconch, here intersected and crossed by much lower spiral cords that form beads at their intersection. Teleoconch sculpture of numerous, prominent, quite uniformly spaced, slightly sinuate, opisthocline radial ribs. Ribs on body whorl 94. Umbilicus wide cup-shaped.

Type material examined. Holotype. QMMO80160 , Gibraltar Range NP, c. 82 km E Glen Innes, Grafton-Glen Innes Rd , north-eastern NSW; (29° 26´S, 152° 23´E), alt. 500m, rainforest, under logs, iii.1981, coll. W. Ponder, J. Stanisic, O. Griffiths, D. Potter. Paratypes. QMMO10858 , QMMO10844 , AM C.128413, all same data as holotype. Gibraltar Range State Forest : AM C.464181.

Description. Shell very small, pale pinkish brown, biconcave with depressed spire. Whorls 4.00, tightly coiled, but the last whorl expanding and descending in front. Sutures strongly impressed. Shell diameter 3.53 mm, height 1.86 mm, H/D 0.53. Protoconch flat, of 1.25 whorls, diameter 0.45 mm. Protoconch sculpture broadly reticulate consisting of 18 prominent, widely spaced, broad, continuous spiral cords that intersect with widely spaced radial ridges on the early part of the protoconch forming a lattice; the ridges developing into widely spaced radial ribs on the latter part of the protoconch, here intersected and crossed by much lower spiral cords that form beads at their intersection. Teleoconch sculpture of numerous, prominent, quite uniformly spaced, slightly sinuate, opisthocline radial ribs. Ribs on body whorl 94, width of interstices on the first teleoconch whorl greater than width of six ribs; on the penultimate whorlequal to width of four to greater than or equal to width of six ribs; each rib with two or more periostracal blades. 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 9–11; on first quarter of body whorl 7–8. Aperture broadly ovately-lunate. Parietal callus prominent, transparent. Umbilicus wide cup-shaped, diameter 1.04 mm, D/U 3.39. Based on 1 measured adult.

Anatomy unknown.

Distribution and habitat. Known only from the Gibraltar Range, north-eastern NSW; found in rainforest, living on underside of logs.

Remarks. Planorbacochlea dandahra n. sp. is distinguished by a broadly reticulate protoconch which has continuous widely spaced spiral cords that intersect weak radial ridges on the early part of the protoconch forming a lattice; on the latter part of the protoconch the ridges develop into widely spaced radial ribs that form beads at their intersection with much lower spiral cords. The micro-architecture of the latter half of the protoconch is not dissimilar from that seen in the Sydney Basin Cumberlandica although these genera are not sister taxa ( Figs 4, 5). There are also some similarities to the reticulate protoconchs of Planorbacochlea yessabahensis , P. nambucca , P. parriwiensis . However, in these latter species the radial elements are dominant over the entire length of the protoconch. The protoconch architecture of both P. yessabahensis and P. nambucca comes closest to that of P. dandahra but these two species differ significantly in coiling pattern in addition to having a depressed spire and Ushaped umbilicus. The reticulate protoconch of P. dandahra has similarities to those of other undescribed species both in the northern rivers area of NSW and the Border Ranges. Molecular results suggest that the species is included in Planorbacochlea . However, the true affinities of P. dandahra will only be established by additional studies of the mid- and north-eastern NSW nautiliform charopids. The protoconch type is more widespread than is indicated by the coverage presented here (unpublished data) and additional studies are needed to determine its full geographic range.

P. dandahra had been previously confused in the QM collections with the sympatric ‘ Gyrocochlea’ gibraltar Stanisic, 2010. However it can readily be separated from that species on general shell morphology. P. dandahra has a weaker biconcave shell and more teleoconch ribs than ‘ G’. gibraltar (94 as opposed to 60). The protoconch of ‘ G’. gibraltar was not scanned and no soft parts were available for molecular studies so that the relationships of this species remain to be determined.