Lamellaria sp., from Sea Slugs of Hawai’i.

Belongs within: Hypsogastropoda.
Contains: Triviidae, Ovulidae, Cypraeidae, Erato.

The Cypraeoidea are a group of marine molluscs with a more or less involute shell, the older (inner) whorls being concealed by the youngest (outer). In life, the shell is mostly covered by lateral extensions of the mantle. As a result, the shells of cypraeoids are typically highly polished. In members of the subfamily Lamellariinae within the Velutinidae, the shell is entirely internal. The Velutininae have a broad-apertured shell like that of Lamellariinae but it remains external with a thick periostracum.

The Velutinidae: sea not-quite-slugs
Published 11 October 2014
Velutinid, probably Lamellaria, copyright Bill Rudman.

In previous posts on this site, I have introduced you to some of the incredible animals that shelter under the misleadingly unprepossessing name of ‘sea slugs’. However, marine mollusc diversity being what it is, it should probably come as no surprise that not all that squashes is slug-y.

The Velutinidae (sometimes referred to in older references as Lamellariidae) are a group of small gastropods that often look rather like sea slugs on the outside, but are misleading it that they actually do have shells. In one subfamily, the Lamellariinae, the mantle has expansive lobes that wrap up around the shell, covering it over. Velutinids are far from being the only molluscs that do this: the glossiness of cowrie shells, for instance, is because live cowries have the shell protected from the elements in this way. Lamellariines differ from cowries, however, in that the mantle lobes are more or less fused to each other and cannot be retracted back. In the other subfamily of Velutinidae, the Velutininae, the shell is not entirely covered by the mantle, as can be seen in the photo below. In both subfamilies, the shell makes it through one or two small loops before broadening out into an abalone-like shape. Lamellariines also differ from velutinines in lacking the marginal teeth of the radula (Beesley et al. 1998).

Velutina prolongata, copyright Dave Cowles.

The velutinids are all specialised predators of ascidians (sea squirts), which they tear into with hard chitinous jaws contained in the buccal mass. The mantle of lamellariines is often coloured to look like the sea squirt they are feeding on, which can make them very difficult to see: to a casual observer, they’re just one more squashy blob amongst a whole bunch of squashy blobs. The unfortunate sea squirts are used as nurseries as well as dinner: the female velutinid inserts each egg capsule into a hole that she bites into the sea squirt, with only a narrow neck protruding from its skin through which the velutinid larva hatches.

Velutinid identified as Coriocella nigra, but looking a bit different from other photos online supposed to be this species, from here.

The velutinids are not close relatives of the classic sea slugs, but closer to gastropods such as cowries and periwinkles. They are regarded by most authors as closest to the Triviidae, a group of cowrie-like gastropods that resemble velutinids in their expanded mantle lobes and preferred diet of ascidians. Velutinids and triviids also resemble each other in having an unusual type of larva called an echinospira. Echinospira larvae appear to have two shells, with a mineralised inner shell that is quite separate from a transparent, glassy outer shell. In the Velutinidae, these two shells even coil differently: the outer shell is planispiral, but the inner shell is helical. When the larva metamorphoses, the outer shell is lost. As a result, earlier authors believed that the inner shell corresponded to the true adult shell, while the outer shell was a novelty unique to echinospirae. In recent times, however, a more popular interpretation is that the two shells each correspond to the inner calcareous layer and the outer periostracum of more usual shells, with their growth having become decoupled. The only other gastropods known to possess an echinospira larva are members of the family Capulidae; whether this larval type indicates that all three families form a single clade remains uncertain.

Echinospira larva of Lamellaria perspicua, from Lebour (1935).
Systematics of Cypraeoidea

Characters (from Simone 2011): Shell involute. Loss of adult operculum. Mantle lobe covering most of outer surface of shell. Part of pericardium lying dorsal to gill. Auricle connecting subterminally to ctenidial vein. Duplication of horizontal muscle (m6) of odontophore.

<==Cypraeoidea (see below for synonymy)S11
    |  |  `--+--OvulidaeS11
    |  |     `--CypraeidaeS11
    |  `--Eratoidae [Eratoinae, Eratooidea]S11
    |       |--EratoM03
    |       |--Johnstrupia Ravn 1933 [Johnstrupiini]BR05
    |       |    `--*J. faxensis Ravn 1933BR17
    |       |--Eratotrivia Sacco 1894 [Eratotriviini]BR05
    |       |    `--E. crenularis Oppenheim 1901 [=Cypraea crenata Deshayes 1835 non Röding 1798, *E. crenata]BR17
    |       `--HespereratoS11
    |            |--H. maugeriae (Gray 1832)S11
    |            `--H. septentrionalis Cate 1977BC01
         |    |--Marsenia Oken 1823BR17, BR05 [Marseniadae, Marseniidae]
         |    |    `--*M. haliotoidea (Montagu 1803) [=Bulla haliotoidea]BR17
         |    |--Capulacmaea Sars 1859BR17, BR05 [Capulacmaeinae]
         |    |    `--*C. radiata (Sars 1851) [=Capulus radiatus]BR17
         |    |--Marseniopsis Bergh 1886BR17, BR05 [Marseniopsidae]
         |    |    |--*M. pacifica Bergh 1886BR17
         |    |    `--M. innominatus Iredale 1936W93
         |    |--Marsenina Gray 1850BR17, BR05 [Marsenininae]
         |    |    |--*M. prodita (Lovén 1846) [=Lamellaria prodita]BR17
         |    |    `--M. rhombica (Dall 1871) [=Lamellaria (Marsenina) rhombica]O27
         |    |--Onchidiopsis Bergh 1853BR17, BR05 [Onchidiopsinae]
         |    |    |--*O. groenlandica Bergh 1853BR17
         |    |    |--O. glacialisO27
         |    |    `--O. hannai Dall 1916O27
         |    `--Velutina Fleming 1820BR05
         |         |--V. velutina (Müller 1776) [=Bulla velutina, *V. vulgaris Fleming 1820]BR17
         |         |--V. conica Dall 1886O27
         |         |--V. coriacea Pallas 1788O27
         |         |--V. cryptospira Middendorff 1849O27
         |         |--V. granulata Dall 1919O27
         |         |--V. laevigata Linnaeus in Müller 1776O27 [=Helix laevigataJ64; incl. V. kamtschatkanaC64, V. muelleriC64]
         |         |--V. plicatilisN79
         |         |--V. prolongata Carpenter 1865O27
         |         |--V. sitkensis Adams 1851O27
         |         |--V. undata [=Galericulum undatum]J64
         |         `--V. zonata Gould 1841O27 [=Morvilia zonataC64]
         `--Lamellariinae [Lamellaridae, Lamellariidae, Trapezodonta]BR17
              |--Pseudosacculus Hirase 1928 (see below for synonymy)BR05
              |    `--*P. okai (Hirase 1927) [=*Sacculus okai]BR17
              |--Coriocella Blainville 1824 [Coriocellacea, Coriocellidae]BR05
              |    |--*C. nigra Blainville 1824BR17
              |    `--C. tongana (Quoy & Gaimard 1832)WBS-S15
              |--Mysticoncha Allan 1936P61
              |    |--M. wilsoni Smith 1886W93 [=Lamellaria wilsoniP61; incl. *M. contusiformisW93]
              |    `--M. harrisonae Powell 1946P61
              |--Chelynotus Bergh 1853W93
              |    |--*C. nigraW93
              |    |--C. semperi Bergh 1866WBS-S15
              |    `--C. tonganus (Quoy & Gaimard 1832)BW09
              `--Lamellaria Montagu 1815BR05
                   |  i. s.: *L. tentaculata Montagu 1815BR17
                   |         L. australis Basedow 1905W93
                   |         L. cerebroides Hutton 1883P61
                   |         L. conica Smith 1902P61
                   |         L. diegoensis Dall 1885O27
                   |         L. digueti (Rochebrune 1895) [=Pleurobranchus digueti]O27
                   |         L. inflata [=Stomatella inflata]C64
                   |         L. inopinata Cossmann 1907TTE93
                   |         L. koto Schwengel 1944BC01
                   |         L. latensN79
                   |         L. ophione Gray 1849W93
                   |         L. perspicuaP61
                   |         L. stearnsii Dall 1871O27
                   |           |--L. s. stearnsiiO27
                   |           `--L. s. orbiculata Dall 1871O27
                   |         L. verrucosa Odhner 1924P61
                   |--L. patagonica Smith 1881S11
                   `--+--L. banca Simone 2004S11
                      `--L. mopsicolor Marcus 1956S11

Cypraeoidea [Cypraeiformes, Lamellariacea, Lamellarioidea, Ovata, Pediculariiformes, Pedicularioidea, Pedicularioidei, Velutinoidea, Velutinoidei]S11

Pseudosacculus Hirase 1928 [=Sacculus Hirase 1927 non Gosse 1851; Pseudosacculidae, Pseudosacculinae, Sacculidae]BR05

*Type species of generic name indicated


Beesley, P. L., G. J. B. Ross & A. Wells (eds) 1998. Fauna of Australia vol. 5. Mollusca: The Southern Synthesis pt B. CSIRO Publishing: Melbourne.

[BR05] Bouchet, P., & J.-P. Rocroi. 2005. Classification and nomenclator of gastropod families. Malacologia 47 (1–2): 1–397.

[BR17] Bouchet, P., J.-P. Rocroi, B. Hausdorf, A. Kaim, Y. Kano, A. Nützel, P. Parkhaev, M. Schrödl & E. E. Strong. 2017. Revised classification, nomenclator and typification of gastropod and monoplacophoran families. Malacologia 61 (1–2): 1–526.

[BC01] Boyko, C. B., & J. R. Cordeiro. 2001. Catalog of Recent type specimens in the Division of Invertebrate Zoology, American Museum of Natural History. V. Mollusca, part 2 (class Gastropoda [exclusive of Opisthobranchia and Pulmonata], with supplements to Gastropoda [Opisthobranchia], and Bivalvia). Bulletin of the American Museum of Natural History 262: 1–170.

[BW09] Bryce, C., & C. Whisson. 2009. The macromolluscs of Mermaid (Rowley Shoals), Scott and Seringapatam Reefs, Western Australia. Records of the Western Australian Museum Supplement 77: 177–208.

[C64] Carpenter, P. P. 1864. Supplementary report on the present state of our knowledge with regard to the Mollusca of the west coast of North America. Report of the British Association for the Advancement of Science 33: 517–686.

[J64] Jeffreys, J. G. 1864. Report of the committee appointed for exploring the coasts of Shetland by means of the dredge. Report of the British Association for the Advancement of Science 33: 70–81.

Lebour, M. V. 1935. The echinospira larvae (Mollusca) of Plymouth. Proceedings of the Zoological Society of London 105 (1): 163–174, pls 1–6.

[M03] Meyer, C. P. 2003. Molecular systematics of cowries (Gastropoda: Cypraeidae) and diversification patterns in the tropics. Biological Journal of the Linnean Society 79: 401–459.

[N79] Norman, A. M. 1879. The Mollusca of the fiords near Bergen, Norway. Journal of Conchology 2: 8–77.

[O27] Oldroyd, I. S. 1927. The Marine Shells of the West Coast of North America vol. 2 pt 3. Stanford University Press: Stanford University (California).

[P61] Powell, A. W. B. 1961. Shells of New Zealand: An illustrated handbook 4th ed. Whitcombe and Tombs Limited: Christchurch.

[S11] Simone, L. R. L. 2011. Phylogeny of the Caenogastropoda (Mollusca), based on comparative morphology. Arquivos de Zoologia 42 (4): 161–323.

[TTE93] Tracey, S., J. A. Todd & D. H. Erwin. 1993. Mollusca: Gastropoda. In: Benton, M. J. (ed.) The Fossil Record 2 pp. 131–167. Chapman & Hall: London.

[WBS-S15] Willan, R. C., C. Bryce & S. M. Slack-Smith. 2015. Kimberley marine biota. Historical data: molluscs. Records of the Western Australian Museum Supplement 84: 287–343.

[W93] Wilson, B. 1993. Australian Marine Shells vol. 1. Prosobranch Gastropods. Part One. Odyssey Publishing: Kallaroo (Western Australia).

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