Lamellariinae, d'Orbigny, 1841

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 : 943-944

Subfamily Lamellariinae

The subfamily Lamellariinae is by far the largest in terms of the number of genera and species. It can be found from shallow to deep sea, in all tropical areas and in the temperate northern Atlantic. Many of the taxa included in this subfamily, even if phylogenetically distant, can have overlapping morphologies, making them very hard to distinguish without a genetic analysis. Traditionally, lamellariine taxonomy is based on a short list of morphological characters, some of which were confirmed in our molecular results to be diagnostic at the genus level (e.g. shape of the radular teeth). The jaws, shell and protoconch can be useful additional characters for those genera showing peculiar shapes but are often similar across the whole subfamily and therefore hard to use alone as diagnostic characters. Regarding shell shape, only macro-differences [such as high vs. low spire, well calcified vs. less calcified (here termed as membranaceus)] are diagnostic. Fretter & Graham (1962: 319–322) described differences between the shells of Lamellaria latens and ‘ Lamellaria ’ perspicua , but in fact, when several specimens, from both sexes and of different sizes, are observed and compared, many of these alleged morphological differences turn out to represent a gradient of shapes overlapping between different species (e.g. Fig. 8C, D ). Bergh (1887) had suggested using the conformation of the vas deferens, forming either a loop or several folds in the haemocoel (between the body wall and the base of the penis), as a genus-level diagnostic character. Simone (2004) considered this character as ‘additive’ because of its ontogeny, because a clearly distinguishable loop was visible only in mature males. Our results suggest that molecular congeners can present different states of this character, and even at the species level its reliability is questionable.

Within the subfamily Lamellariinae , diagnosed by a synapomorphic radula lacking marginal teeth (formula 0:1:1:1:0), we recognize the following seven phylogenetic lineages consistent with genus-level taxonomic ranking: Calyptoconcha Bouchet & Warén, 1993 (‘F’), Variolipallium Fassio, Bouchet & Oliverio (‘G’), Pacifica Fassio, Bouchet & Oliverio (‘H’), Djiboutia Vayssière, 1912 (‘I’), Coriocella (‘J’), Lamellaria (‘K’) and Marsenia Oken, 1823 (‘L’); plus Marseniella , not present in our molecular dataset.

Figures

Figure 8. Velutinidae shells. A, Djiboutia sp. (L26), MNHN-IM-2019-7668. B, Coriocella sp. (L27), MNHN-IM-2013-84230. C, Lamellaria latens complex (L41), MNHN-IM-2019-14179. D, Marsenia perspicua complex (L55), MNHN-IM-2019-14574. Scale bars: A, C, D, 1 mm; B, 5 mm. For the sequenced specimens, the corresponding species code (see Fig. 3) is reported in parentheses.