Planorbacochlea, Shea & Colgan & Stanisic, 2012

Shea, M., Colgan, D. J. & Stanisic, J., 2012, 3585, Zootaxa 3585, pp. 1-109 : 36-37

Planorbacochlea n. gen.

Gyrocochlea Hedley, 1924: 215 (in part); Iredale 1937: 322 (in part); Iredale 1941a: 267 (in part); Smith 1992: 190 (in part); Stanisic et al. 2010: 196 (in part).

Type species. Gyrocochlea hawkesburyana Stanisic, 2010 —here designated.

Etymology. From the Latin planus = flat, orbis = disc and cochlea = snail.

Diagnosis. Shell very small to small, brownish, with a weakly to strongly depressed spire and tightly coiled whorls, the last inflated. Protoconch sculpture of prominent crowded, beaded spiral cords and low radial undulations ( P. hawkesburyana , P. planorbis ), or with more widely spaced spiral cords and equally high, narrow, widely spaced radial ribs ( P. reticulata ) to widely reticulate with widely spaced non-beaded, spiral cords and broad radial ribs of equal prominenence ( P. parriwiensis , P. yessabahensis and P. nambucca ). Teleoconch with numerous well developed, widely to very closely spaced, prominent radial ribs; microsculpture cancellate with prominent microradial ribs and low microspiral cords. Aperture broadly, ovately-lunate. Umbilicus U-shaped to wide cupshaped. Penis tubular to pear-shaped, with longitudinal pilasters distally, with an apical verge that has a lateral or terminal pore or without a verge ( P. nambucca , P. reticulata ). Epiphallus generally as long as penis.

Distribution and habitat. Sydney Basin north to the Nambucca River drainage, NSW; found in a variety of habitats including dry sclerophyll forest but more commonly in vine thicket/rainforest associations, usually in small groups living on the undersides of logs and timber.

Remarks. Planorbacochlea n. gen. Differs from Cumberlandica primarily on general shell form and in the sculpture of the protoconch. Planorbacochlea has a more tightly coiled whorl profile with inflated last whorl and strongly spiral to reticulate protoconch sculpture. Cumberlandica has evenly coiled whorls and a protoconch that has bi-modal sculpture consisting of spirals initially and dominant radials on the latter part.

Planorbacochlea is a geographically widespread and diverse group when compared with other genera dealt with here. It is also considered highly problematic in composition. While the DNA results identify the group as coherent, the protoconch and anatomical data show a number of significant anomalies. The protoconch sculpture in Sydney Basin Planorbacochlea and P. planorbis generally exhibits a spiral pattern comprising closely spaced, fine beaded spiral cords (but less closely spaced then in Gyrocochlea s.s.) and weak radial ridges. However, in P. parriwiensis n. sp. (sympatric with P. hawkesburyana n. sp.), P. yessabahensis n. sp., P. nambucca n. sp. P. reticulata n. sp. and P. dandahra n. sp. the protoconch sculpture is reticulate and is comprised of spiral cords that are more widely spaced and more prominent widely spaced radial elements. Furthermore, P. nambucca n. sp., in lacking a penial verge, also differs radically in reproductive tract morphology from all other species in the group. These morphological differences are of the same order of magnitude as those between other genera treated here. Considering the difficulty with the collection of these charopids in the field alluded to earlier, there is a reasonable likelihood that additional species, yet to be discovered, exist within the broad landscape currently defined by the Planorbacochlea distribution. These may yet assist in adequately defining Planorbacochlea . However, additional fieldwork, which was outside the resources of the current study, is needed to resolve this problem.

Further north in the Clarence and Richmond River drainages, and in the Border Ranges, there are also yet-tobe described species which could be embraced in the general concept of this genus as it currently stands. However, the differences in the fine detail of the reticulate protoconch sculpture in these species are also such as to suggest that they represent separate lineages from Planorbacochlea . Their inclusion in the genus would lead to a situation similar to that of Gyrocochlea s.l., which the current study seeks to unravel.