Pravonitor stuarti, Hyman & Köhler, 2022

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), Journal of Natural History 56 (41 - 44), pp. 1727-1799 : 1788-1790

Pravonitor stuarti sp. nov.

( Figures 4 , 14 (i), 21)

Etymology

Named for Stuart Palethorpe.

Material examined

Holotype. QM MO86002 , High Range , Far North Qld (13.05° S, 143.45° E), 3 November 2012, K. Aland.

Paratype. QM MO80213 (same data as holotype) .

Other material examined. See Table 1 .

Diagnosis

External morphology. Shell ( Figure 14 (i)) medium-sized (SW 12.1–13.6 mm), pale gold above, pale amber below, with an amber supraperipheral band, 5.2–5.5 whorls, discoidal with a moderately elevated, slightly concave spire, whorls rounded, umbilicus very narrow, sealed with a mucous plug, partially covered by reflected lip. Protoconch and teleoconch sculptured with very fine spiral grooves, hardly visible on protoconch. Body cream, with dark grey tail (incl. caudal horn), pale grey head, pale sole, grey band along side of foot (in alcohol). Right and median mantle lobes moderate, left lobe moderately small; right lobe grey and cream, median lobe dark grey, left lobe cream; shell lappets long, wide at base, tapering to a point. Caudal horn very long.

Genital anatomy. Genitalia ( Figure 21 ) with short vagina; bursa copulatrix moderately long, duct broad at base, becoming narrower, coiled, bursa elongate, internally sculptured with transverse ridges basally and longitudinal ridges in duct. Penis very long and narrow, tubular, slightly broader at base, narrower in middle, broadening slightly after exiting penial tunica and slightly swollen near epiphallic boundary; internally with multiple narrow longitudinal pilasters; approx. 80% enclosed in penial tunica. Two penial caecae inserted on penis near base, inside penial tunica; one short, one longer. Epiphallus enters penis through a small verge; epiphallus slightly longer than penis; epiphallus 2 longer than epiphallus 1; long epiphallic caecum present, with medial attachment of the penial retractor muscle; flagellum long, slender, slightly swollen terminally, with no obvious internal cryptae.

Remarks

Pravonitor stuarti is very similar in appearance to P. ferrugineus , and was originally identified as belonging to this species. However, in the current study a population of P. ferrugineus from High Range was found to have a larger and flatter shell with a more concave spire, while still exhibiting the typical cream-coloured shell with a reddish brown supraperipheral band characteristic of the species. Dissection showed that these specimens differed in penis size, shape and interior sculpture, and in the shape of the flagellum. In particular, while the penis was still long and slender with a thick penial tunica, it was longer and more uniformly narrow in P. stuarti , with a small penial verge and interior sculpture of longitudinal ridges rather than the pointed pustules seen in P. ferrugineus . In addition, the flagellum of P. stuarti is slender and uncoiled, while that of P. ferrugineus is coiled and shows some signs of small internal cryptae, indicating the presence of a coiled spermatophore with small spines (similar to that seen in P. annulus ). A single specimen of P. stuarti has been sequenced, and shows it to be the basal member of genus Pravonitor , but also that it is nearly identical to P. ferrugineus . Despite this, we feel that the very distinct reproductive system, particularly the strikingly distinct sculpture of the inner penial wall, indicates that the two morphospecies must be reproductively isolated.

Only a single spirit-preserved lot of P. stuarti is known, from High Range, south of Lockhart River on Cape York peninsula ( Figure 4 ). Pravonitor ferrugineus is found slightly to the north, in Iron Range National Park. It is possible that the two species are sympatric, but currently very little data is available for either species. The very distinct differences in the penial sculpture seen in the two species would ensure reproductive isolation, even in sympatry. Increased collecting on Cape York is needed to clarify the range of this species.

Pravonitor stuarti can be distinguished from most other species by its cream shell and rust-coloured supraperipheral band, and from Pravonitor ferrugineus by its larger size, flatter shell and more concave spire, as well as differences in its genital morphology.

Figures

Figure 4. Distribution map. Grey symbols: Geminitor. Blue symbols: Pravonitor. Red symbols: Elatonitor. Biogeographic barriers are marked in black; A = Normanby Basin, B = Black Mountain Corridor, and C = Atherton Tableland.

Figure 14. Shells of Pravonitor. a) Pravonitor insularum, AM C.170795 (paratype). b) Pravonitor annulus AM C.425415,Gabba Is. c) Pravonitor aquilonia, QM MO48285 (holotype). d) Pravonitor ferrugineus, QM MO12752 (holotype). e). Pravonitor kreffti, AM C.1352, Thursday Is. f) Pravonitor kreffti, AM C.425474, Simpson’s Bay, Utingu. g) Pravonitor monteithi, QM MO48587 (holotype). h) Pravonitor septentrionalis, AM C.425422. i) Pravonitor stuarti, QM MO80213 (paratype). Scale bar: 5 mm.

Figure 21. Genitalia of Pravonitor stuarti, QM MO86002 (holotype), High Range. a) Reproductive system. b) Penis with tunica opened. c) Penis with tunica opened, opposite orientation to b). d) Penis interior. Scale bars: 1 mm.