Calyptoconcha, BOUCHET & WAREN, 1993

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 : 951-952

CALYPTOCONCHA BOUCHET & WARÉN, 1993

( FIGS 2 , 3 , 7A , 9C , 10D , 11D )

Calyptoconcha Bouchet & Warén, 1993: 742 .

Type species Lamellaria pellucida A. E. Verrill, 1880 , by original designation.

Included species: Calyptoconcha branca ( Simone, 2004) comb. nov., Calyptoconcha capensis ( Bergh, 1907) comb. nov., Calyptoconcha pellucida (A. E. Verrill, 1880) .

Description: Body of small to medium size for the subfamily, 1–4 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. Periostracum not visible.

Protoconch of 1.77–1.80 whorls; protoconch I of 0.58–1.00 whorls, smooth, nucleus diameter 54–75 μm; protoconch II with axial growth lines; protoconch– teleoconch boundary not always distinct.

Mantle flat or dome shaped, outline rounded; thick to very thick, with anterior and right lateral siphon folds; texture smooth or wrinkled; colour variability unknown.

Penis to the right of the right cephalic tentacle, with a subterminal lateral papilla. Vas deferens with a free loop in haemocoel.

Radula reduced taenioglossate, formula 0:1:1:1:0; rachidian tooth base squared; rachidian cusp with several small external denticles; lateral teeth elongated, triangular with a single external pointed cusp, with several small denticles on both sides.

Jaws homogeneous, short, with a small vertical protrusion in the centre.

Distribution: Northern temperate Atlantic, Alboran Sea, South Africa, Brazil, Uruguay; 58–4500 m deep.

R e m a r k s: T h e g e n u s C a l y p t o c o n c h a c a n b e distinguished by the combination of a reduced taenioglossate radula (formula 0:1:1:1:0), a rachidian tooth with a squared base, and a non-calcified internal vestigial shell (often broken in dredged specimens and difficult to remove from the body) with a comparatively higher spire. The protoconch is also different from the rest of the subfamily in having a small diameter of the nucleus, a small diameter of the first whorl and lacking subsutural axial folds on protoconch I. The jaws show a diagnostic small vertical protrusion in the centre.

Based on the radular formula, the shape of the rachidian tooth and composition of the shell, we include in this genus the South African Marsenia capensis (Cape Point, 239–1463 m). We also suggest including Lamellaria branca (type locality: Brazil, off Sao Paulo state, in 78 m) based on its radula and shell shape, although the shell seems to be calcified compared with the other two congeners, which might be related to its shallower water habitat.

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 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.