Pravonitor annulus
Creators: name: Hyman, Isabel T.
name: Köhler, Frank
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Gastropoda
Stylommatophora
Helicarionidae
Pravonitor
Pravonitor annulus

description: Pravonitor annulus (Brazier, 1876)
(Figures 4, 14 (b), 15)
Helix (Thalassia) annulus Brazier, 1876: 100.
Pravonitor annulus: Iredale 1941: 65.
Pravonitor kreffti: Hyman and Ponder 2010: 64–65, figs 17 M–0, 18 G, 19 H–I, 20 G–H, 21 H– I, 22C (in part).
Material examined
Syntypes. AM C.171131, C.171132, Mawatta (Marrahata) Village, Binaturi (Katow) River mouth, New Guinea, 09° 08’ 15” S, 142° 57’ 00” E, coll. Brazier, July 1975.
Probable syntypes. AM C.55456, Binaturi (Katow) River, New Guinea, 09° 08’ 15” S, 142° 57’ 00” E, coll. J. Brazier, July 1875), C. 104171 (Torres Strait, Dungeness Island, 09° 51’ 00” S, 142° 54’ 00” E, coll. J. Brazier, 20 July 1875.
Other material. See Table 1.
Diagnosis
External morphology. Shell (Figure 14 (b)) medium-sized (SW 12.6–15.8 mm), golden brown with a darker supraperipheral band, 5.7–6.2 whorls, subdiscoidal with a subangulate whorl profile; shell microsculpture with fine grooves on the protoconch and teleoconch, becoming obsolete on the teleoconch; umbilicus narrow, sealed with a mucous plug, partially covered by reflected lip. Body cream (in alcohol). Mantle lobes moderately small; shell lappets moderately large, narrow, tapering. Caudal horn large.
Genital anatomy. Genitalia (Figure 15) with short vagina, internally with wavy longitudinal pilasters; bursa copulatrix moderately short, duct narrow, internally with wavy transverse pilasters, bursa elongate. Penis tubular, with one longitudinal pilaster, internal wall sculptured with pustules, smaller and rounded proximally, larger and more diamondshaped distally; approx. 75% enclosed in penial tunica. Epiphallus enters penis through a small verge; epiphallus longer than penis; epiphallus 2 longer than epiphallus 1; long epiphallic caecum present, with medial attachment of the penial retractor muscle; flagellum long, spiralling, containing internal cryptae.
Remarks
This species (preliminarily identified above as P. kreffti ‘Central Islands’) was first introduced as Helix (Thalassia) annulus (Brazier, 1876) for a species from Mawatta Village, on the banks of the Binaturi River, New Guinea (given as Marrahata Village, Katow River), and Giaka (= Dungeness) Island, from the Central group of islands in the Torres Strait. The specimens were collected in 1875 on the Chevert Expedition to New Guinea. Iredale (1937) introduced a replacement name for the Torres Strait Islands populations (Helix (Pravonitor) kreffti insularum, type locality Mer Island), presumably assuming that the New Guinean annulus would not also extend to the Torres Strait Islands. The type material was assumed to be lost and so this species was regarded as not applying to any Australian species (Smith 1992).
However, after careful examination of the original material in the current study and comparison with shells from multiple other islands in the Torres Strait, we have concluded that this species is a member of the genus Pravonitor and that it is found at the type locality in New Guinea, as well as on the Top Western and Central groups of Torres Strait Islands, including Dauan, Iama, Gerber and Giaka Islands (Figure 4).
The syntypes are mostly juvenile shells, with only three approaching adult size, at 5.1– 5.4 whorls. All specimens have golden, shining shells with a distinct band, and a whorl profile that is rounded above and below a slightly angulate periphery.
In the case of both P. insularum and P. annulus, the lack of fresh, adult material from the type localities and from throughout the Torres Strait Islands significantly impedes the process of name clarification. It is possible that the Mer Island specimens may prove to be conspecific with the Central Islands species, in which case P. insularum will become a junior synonym of P. annulus. Our intent is to take the most conservative path and to avoid either introducing new names or placing names in synonymy based on incomplete data. For that reason, we retain P. insularum for Mer Island populations and P. annulus for both New Guinean and Top Western/Central Island populations at the present time, pending further investigation.
Pravonitor annulus can be distinguished from P. kreffti (found on the Inner and Near Western Islands) by its slightly smaller and more depressed shell with a subangulate whorl profile and a supraperipheral band, and by differences in the genital anatomy, including the presence of a cylindrical penis with no blind tip, a very long epiphallic caecum with medial attachment of the penis retractor muscle, and a coiled flagellum with internal cryptae. This contrasts to the broad penis with a large blind tip, relatively short epiphallus with the penis retractor muscle attaching at or near the tip, and the straight flagellum with no externally visible cryptae of P. kreffti. It is not clear whether the two species co-exist on any islands; targeted collecting in this region would help to delimit species distributions and clarify the differences between the two species.
description: Published as part of Hyman, Isabel T. & Köhler, Frank, 2022, Homoplasy in shells discombobulated the taxonomy: revision of the larger helicarionid land snails of northern Queensland, Australia (Stylommatophora: Helicarionidae), pp. 1727-1799 in Journal of Natural History 56 (41 - 44) on pages 1775-1777, DOI: 10.1080/00222933.2022.2136017, http://zenodo.org/record/7380681