Variolipallium, FASSIO, BOUCHET & OLIVERIO, 2023

Fassio, Giulia, Stefani, Matteo, Russini, Valeria, Buge, Barbara, Bouchet, Philippe, Treneman, Nancy, Malaquias, Manuel António E., Schiaparelli, Stefano, Modica, Maria Vittoria & Oliverio, Marco, 2023, Neither slugs nor snails: a molecular reappraisal of the gastropod family Velutinidae, Zoological Journal of the Linnean Society 197 (4), pp. 924-964 : 952-953

VARIOLIPALLIUM FASSIO, BOUCHET & OLIVERIO GEN. NOV.

( FIGS 2 , 3 , 4H–J , 7B , 9D , 10E, F , 11E, F )

Zoobank registration: urn: lsid: zoobank. org:act: 170D2A4B-E62D-4612-9737-FFC39B639EFA

Type species: Variolipallium regium Fassio, Bouchet & Oliverio sp. nov.

Included species: Variolipallium cerebroides (Hutton, 1882) comb. nov., Variolipallium elatum (Strebel, 1906) comb. nov., Variolipallium leptoconcha ( Bergh, 1907) comb. nov., Variolipalliumnodosum (Ev.Marcus, 1987) comb. nov., Variolipallium patagonicum (E. A. Smith, 1881) comb. nov. and Variolipallium regium Fassio, Bouchet, Oliverio sp. nov.

Description: Body of small to medium size for the subfamily, 0.5–3.0 cm total length. Shell very thin, weakly calcified to membranaceus; ear shaped, high spired, with expanded aperture; smooth or weakly sculptured by axial growth lines; completely enclosed by the mantle or presenting a small dorsal fissure. Periostracum not visible.

Protoconch of 1.24–1.70 whorls; protoconch I of 0.48– 1.20 whorls, nucleus diameter 100–150 μm, smooth, with subsutural axial folds; protoconch II with axial growth lines; protoconch–teleoconch boundary not always distinct.

Mantle flat or dome shaped, outline rounded or polygonal; thick to thin, often with a few to several dorsal tubercles; with anterior siphon fold; texture smooth to wrinkled (resembling the convolutions of a brain); colour variable, almost transparent to white, grey, yellow, orange to red, pink to violet, light blue, brown, dark green, occasionally patterned with spots. Cephalic tentacle tips can be white, lime yellow or almost transparent.

Penis to the right of the right cephalic tentacle, with or without a lateral subterminal papilla. Vas deferens without a free loop in haemocoel.

Radula reduced taenioglossate, formula 0:1:1:1:0; rachidian tooth base bifurcated; rachidian cusp with few to several, very small to pronounced external denticles; lateral teeth elongated, with a pointed triangular external cusp, with few to several, very small to pronounced denticles on both sides or only on the internal side.

Jaws homogeneous, short to elongated.

Distribution: Tropical West Pacific (South China Sea, Papua New Guinea, New Caledonia), New Zealand; Caribbean; tip of South America ( Chile, Argentina, Falkland Islands), South Africa; 42–1573 m deep.

Etymology: From Variola , the Latin name for smallpox, and pallium, meaning ‘mantle’, referring to the coloured small tubercles on the mantle of the type species and other members of the group. Gender neuter.

Remarks: Variolipallium can be diagnosed by a membranaceous to weakly calcified shell with high spire (similar to that of Calyptoconcha and Marseniopsis ) and a bifurcated rachidian tooth (like Lamellaria , Marsenia , etc.), although in Variolipallium the ‘V’-shaped base of the rachidian tooth can be comparatively less marked.

All the species included in this genus have been found at depths> 95 m.

The dorsal appearance of the mantle varies from wrinkled, with several tubercles (resembling the convolutions of a brain), to rather smooth and studded with fewer small tubercles of different colour, to completely smooth. Several species ( Variolipallium cerebroides , Variolipallium cf. patagonicum , Variolipallium cf. elatum , Variolipallium sp. L10, Variolipallium sp. L11, Variolipallium sp. L12, Variolipallium sp. L14 and Variolipallium regium ) include specimens with a small to very small dorsal mantle fissure, occasionally marked by a small black spot (visible also in preserved specimens).

Lamellaria patagonica E. A. Smith, 1881 (type locality: Trinidad Channel, Chile, in 54 m) and Lamellaria elata Strebel, 1906 (type locality: Puerto Condor, Chile) belong to this genus based on their fragile and high-spired shells, smooth mantle and radular formula and shape. Variolipallium patagonicum and Variolipallium elatum can be distinguished by a more rapidly expanding first whorl in the former and, consequently, a higher shell in the latter, also resulting in a flatter body in Variolipallium patagonicum and a more globose one in Variolipallium elatum .

Lamellariaampla Strebel, 1906 (Ushuaia, Argentina) might also belong here (based on shell shape and shell consistency), but further analysis of the type material is necessary, because the radula, in particular, is not described in the original description. However, the general description, in particular the jelly-like mantle, wrinkled, grey with darker spots, would also be compatible with a position in Marseniopsinae .

Lamellaria leptoconcha ( South Africa, Cape Point, in 1097–1280 m) is included in Variolipallium based on the membranaceus texture of the shell and the shape of the rachidian tooth. Bergh (1907: pl. IX, fig. 18) sketched a rachidian tooth with a not marked but visible ‘V’-shaped base (similar to our SEM photographs; Fig. 10E, F ), and in the description underlined that the difference between this species and Marsenia leptolemma (= Calyptoconcha pellucida ) was the shape of the rachidian tooth (that in Calyptoconcha indeed has a squared base).

Lamellaria cerebroides (Auckland, New Zealand) is included in Variolipallium based on the radular formula and shape, and the wrinkled dorsum appearance. Lamellaria Ʋerrucosa (= Lamellaria nodosa ) (Auckland Islands) is also included in this genus based on the membranaceus texture of the shell, the rugose appearance of the dorsum, and the radular formula and shape. Odhner (1924) described it as being similar to Marseniopsis mollis , but the radular formula of Lamellaria Ʋerrucosa clearly indicates that it belongs to the subfamily Lamellariinae .

The original description of Lamellaria ophione Gray, 1850 is general (fitting most lamellariine genera) and does not report any information regarding diagnostic characters. However, considering the type locality (Auckland, New Zealand), there is a chance that this species also belongs to this genus, because this is the only lamellarine genus recorded in this area so far.

Figures

Figure 2. Phylogenetic relationships of the family Velutinidae (Bayesian tree based on the combined dataset), with clades (A–L) collapsed by genera. Numbers at nodes indicate branch support values [posterior probability (PP) and ultrafast bootstrap (UFb) values, respectively]; support values are shown only when at least one of them is ≥ 80%; white circles at nodes indicate maximum support (PP = 1, Ufb = 100). On the right side of the tree, for each genus is reported a representative photograph of the shell, a schematic representation of the radula, the depth range (in metres) and the geographical distribution.

Figure 3. Phylogenetic relationships of the family Velutinidae (Bayesian tree based on the combined dataset) showing clades A–L expanded. Numbers at nodes indicate branch support values [posterior probability (PP) and ultrafast bootstrap (UFb) values, respectively]; support values are shown only when at least one of them is ≥ 80%; white circles at nodes indicate maximum support (PP = 1, Ufb = 100). Boxes indicate hypothetical species; dashed lines indicate possible alternative species partitions. Coloured boxes on the right indicate genera, and white boxes indicate subfamilies. Letters at the end of sample codes broadly indicate the area of origin:AK, Alaska; ANT, Antarctica; AR, Argentina; BC, British Columbia; BRE, Bretagne; CA, California; CH, China; COR, Corse; CR, Costa Rica; FL, Florida; GF, French Guiana; GP, Guadeloupe; HI, Hawaii; IT, Italy; MG, Madagascar; MQ, Martinique; MX, Mexico; MZ, Mozambique; NC, New Caledonia; NL, Newfoundland; NO, Norway; OR, Oregon; PA, Panama; PF, French Polynesia; PG, Papua New Guinea; PH, Philippines; QLS, Queensland; RE, Reunion; SA, Saudi Arabia; SP, Spain; TAS, Tasmania; TW, Taiwan; VU, Vanuatu; WA, Washington State; ZNZ, Zanzibar.

Figure 4. A, Marseniopsis sp. (M9), MNA 5376. B, Marseniopsis conica, MNA 5361. C, Marsenina zadei, LACM 182861. D, Marsenina rhombica, LACM 182862. E, Limneria prolongata, LACM 182858. F, Velutina sp., LACM 182869. G, Hainotis sharonae. H, Variolipallium regium sp. nov., MNHN-IM-2013-69285, holotype. I, Variolipallium sp. (L3), MNHN-IM-2013-69605. J, Variolipallium sp. (L10), MNHN-IM-2013-69280. Photograph credits: A, B, MNA, Stefano Schiaparelli; C–F, Nancy Treneman; G, iNaturalist, Robin Gwen Agarwal; H–J, MNHN, Philippe Maestrati. For the sequenced specimens, the corresponding species code (see Fig. 3) is reported in parentheses.

Figure 7. Velutinidae shells. A, Calyptoconcha pellucida, BAU 3758. B, Variolipallium cerebroides, NIWA 74086.A. C, Pacifica lentiginosa sp. nov., MNHN-IM-2009-16140, holotype. D, Pacifica sp. (L16), MNHN-IM-2013-58543. Scale bars: A, B, 5 mm; C, D, 1 mm. For the sequenced specimens, the corresponding species code (see Fig. 3) is reported in parentheses.

Figure 9. Velutinidae protoconchs. A, Marseniopsis conica, BAS 03-764. B, Marsenina rhombica, BAU 4229. C, Calyptoconcha pellucida, BAU 3758. D, Variolipallium cerebroides, NIWA 74086.A. E, Pacifica lentiginosa sp. nov., MNHN-IM-2009-16140, holotype.F, Pacifica sp. (L16), MNHN-IM-2013-58543. G, Djiboutia sp. (L22), MNHN-IM-2019-9053. H, Coriocella sp. (L27), MNHN-IM-2013-84230. I, Lamellaria latens complex (L41), MNHN-IM-2019-14179. J, Lamellaria mopsicolor, MNHN-IM-2013-73086. K, Marsenia perspicua complex (L55), MNHN-IM-2019-14574. L, Marsenia sp. (L42), MNHN-IM-2019-7641. Scale bars: A–L, 500 µm. For the sequenced specimens, the corresponding species code (see Fig. 3) is reported in parentheses. Arrows indicate protoconch I – protoconch II boundary.

Figure 10. Velutinidae radulae. A, Marseniopsis mollis, CE 6137. B, Marsenina rhombica, BAU 4229. C, Velutina cf. coriacea, LACM 182870. D, Calyptoconcha pellucida, BAU 3751. E, Variolipallium regium sp. nov., MNHN-IM-2013-69285, holotype. F, Variolipallium sp. (L10), MNHN-IM-2013-69280. G, Pacifica lentiginosa sp. nov., MNHN-IM-2009-16140, holotype. H, Pacifica sp. (L15), MNHN-IM-2013-59969. I, Djiboutia sp. (L22), MNHN-IM-2019-9053. J, Coriocella sp. (L27), MNHN-IM-2013-84230. K, Lamellaria mopsicolor, MNHN-IM-2013-73086. L, Lamellaria latens complex (L41), MNHN-IM-2019-14113. M, Marsenia herberti, MNHN-IM-2019-8503. N, Marsenia sp. (L45), MNHN-IM-2013-59960. O, Marsenia perspicua complex (L55), MNHN-IM-2019-5980. Scale bars: A–O, 100 µm. For the sequenced specimens, the corresponding species code (see Fig. 3) is reported in parentheses.

Figure 11. Velutinidae jaws. A, M, Marseniopsis mollis, CE 6152. B, N, O, Marsenina rhombica, BAU 2339. C, Limneria prolongata, BAU 4228. D, Calyptoconcha pellucida, BAU 3758. E, Variolipallium regium sp. nov., MNHN-IM-2013-69285, holotype. F, Variolipallium sp. (L10), MNHN-IM-2013-69280. G, Pacifica lentiginosa sp. nov., MNHN-IM-2009-16140, holotype.H, Pacifica sp. (L19), MNHN-IM-2009-16136.I,Djiboutia sp.(L22), MNHN-IM-2019-9053.J,Coriocella cf.jayi (L28), MNHN-IM-2009-16119. K, Lamellaria latens complex (L40), BAU 2536.2. L, Marsenia sp. (L45), MNHN-IM-2013-59960. Scale bars: H, M–O, 100 µm; A–G, I–L, 500 µm. For the sequenced specimens, the corresponding species code (see Fig. 3) is reported in parentheses.