VELUTININAE GRAY, 1840

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 : 950

VELUTININAE GRAY, 1840

( FIGS 2 , 3 , 4C–F , 6C, D , 9B , 10B, C , 11B, C, N, O )

Velutininae Gray, 1840: 90 ;

type genus Velutina J. Fleming, 1820 .

Marseninidae Odhner, 1913: 9 [as Marsenininae];

type genus Marsenina Gray, 1850 .

Sacculidae Thiele, 1929: 266 ;

type genus Sacculus Hirase, 1927 [permanently invalid, being the type genus a junior homonym of Sacculus Grosse, 1851 (Rotifera) ].

Pseudosacculidae Kuroda, 1933: 186 [replacement name for Sacculidae Thiele ];

type genus Pseudosacculus Hirase, 1928 .

Capulacmaeidae Golikov & Gulbin, 1990: 108 [as Capulacmaeinae];

type genus Capulacmaea M. Sars, 1859 .

Included genera: CartilagoƲelutina Golikov & Gulbin, 1990 , CiliatoƲelutina Golikov & Gulbin, 1990 , Cilifera Golikov & Gulbin, 1990 , Limneria H.Adams & A. Adams, 1851 , Marsenina Gray, 1850 , Onchidiopsis Bergh, 1853 , Piliscus Lovén, 1859 , Pseudosacculus Hirase, 1928 , Pseudotorellia Warén, 1989 , TorelliƲelutina J. H. McLean, 2000 , Velutina J. Fleming, 1820 .

Description: Body of small to medium size for the family, 0.5–11.0 cm total length. Shell moderately thin to thick, weakly to strongly calcified; ear, shield or cap shaped, low to high spire, with expanded aperture; smooth or weakly sculptured by axial growth lines; exposed or completely enclosed by the mantle. Periostracum moderately or well developed, occasionally hairy.

Protoconch of 1.1–2.0 whorls; protoconch I of 0.50– 0.64 whorls, nucleus diameter 125–186 μm, smooth or with microgranules; protoconch–teleoconch boundary not always visible.

Mantle flat or dome shaped, outline rounded; thick or thin, with or without dorsal tubercles; with or without anterior and right lateral siphonal folds; texture smooth, wrinkled or jelly-like; colour highly variable, almost transparent to white, grey, beige, yellow, orange, brown, often patterned.

Penis to the right of the right cephalic tentacle, with tip of the seminal duct protruding from the penis tip. Vas deferens without a free loop in haemocoel.

Radula taenioglossate, formula 2:1:1:1:2, rachidian tooth squared, with broad base, rachidian cusp with or without one to six pronounced external denticles; lateral teeth squared or elongated, with a pointed triangular internal or external cusp, with or without one to six denticles on both sides; marginals narrow, with or without one small denticle on the internal side.

Jaws short to elongated, composed of scale-like elements, with denticles on the masticatory margin.

Distribution: Arctic and temperate regions worldwide, 0–1200 m deep.

Remarks: Velutinines can be diagnosed by their squared rachidian tooth with a broad base, and the jaws composed of scale-like elements, with denticles. Their shells can range from strongly calcified and completely exposed (e.g. Velutina ) to almost without calcification and completely enveloped by the mantle (e.g. Onchidiopsis ). Some genera (e.g. Velutina and Limneria ) also have a hairy periostracum. In addition to the anterior inhalant siphon, an exhalant siphon is made by a right lateral mantle fold in some genera (e.g. Marsenina and Onchidiopsis ). Before the present study, six genera (two of them with subgenera; see Gulbin & Golikov, 1997) were classified in this subfamily. However, the present molecular phylogeny suggests that Limneria and Velutina might be synonyms. In addition, pending molecular analysis of the type material, we propose to place Pseudosacculus in this subfamily, based on the description of the only included species, Pseudosacculus okai ( Hirase, 1927) . The radular formula (2:1:1:1:2) and morphology ( Hirase, 1927: 125, fig. 8) and the presence of a small dorsal aperture in the mantle are congruent with this placement. It should be noted that Pelseneer (1935) suggested that Pseudosacculus okai might be classifiable in Marsenina , which would make Pseudosacculus a junior synonym.

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 6. Velutinidae shells. A, Marseniopsis conica, BAS 03-764. B, Hainotis sharonae, LACM 1059, holotype (after Willet, 1939: fig. 1 and 1a). C, Marsenina rhombica, BAU 4229. D, Limneria prolongata, BAU 4228. Scale bars: A, 1 mm; C, D, 5 mm; B, shell maximum diameter = 5.5 mm, shell height 7.4 mm.

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.