Scaphopoda

Antalis vulgaris, copyright Malcolm Storey.


Belongs within: Rostroconchia.
Contains: Siphonodentaliidae, Dentalium.

The Scaphopoda, tusk shells, are a group of benthic molluscs with a tubular shell that live buried in the sediment, feeding on micro-organisms. In members of the Dentalioida, the shell generally tapers evenly, whereas Gadilida commonly have the shell constricted toward the mouth. The two lineages also differ in foot morphology: Dentalioida have the foot with an encircling sheath that is expanded laterally and interrupted dorsally; Gadilida have the foot simple and vermiform, or distally expanded into a symmetrical disc (Ludbrook 1960).

Characters (from Ludbrook 1960): Marine, bilaterally symmetrical mollusks protected by an external elongate, tubular, tapering, calcareous shell, open at both ends and generally somewhat curved. Concave side of shell dorsal, convex side ventral; aperture or anterior opening larger, apex or posterior opening simple or variously slit or notched, some forms with terminal pipe. Shell substance of three distinct layers. Shell secreted by mantle of same shape, larger (anterior) opening of which is contracted by muscular thickening of mantle, giving egress to long conical foot; smaller (posterior) opening serving as outlet for organic waste and genital products. Mouth furnished with radula, borne on cylindrical snout and surrounded by rosette of lobes; a cluster of threadlike, distally enlarged appendages known as “captacula” springing from its base. No eyes or tentacles; otocysts present. Liver 2-lobed, symmetrical; gut strongly convoluted, anus ventral and somewhat anterior, kidney openings near it. Heart rudimentary; no gills, respiration performed by general integument. Nervous system with well-developed ganglia united by commissures. Gonad simple, sexes separate, reproduction without copulation.

<==Scaphopoda [Cirrhobranchiata, Lateribranchiata]
    |  i. s.: Calstevenus Yancey 1973 PR79
    |         Paleodentalium Gentile 1974 PR79
    |         Quasidentalium Gentile 1974 PR79
    |         Throopella Greger 1933 [Throopellidae] L60
    |           `--*T. typa Greger 1933 L60
    |--Gadilida MG-H11
    |    |--Siphonodentaliidae L60
    |    `--Entalinidae MG-H11
    |         |--Dischides Jeffreys 1867 MG-H11, L60 [=Discides Sacco 1897 L60]
    |         |    `--*D. politus (Wood 1842) [=Ditrupa polita, Cadulus (*Dischides) politus] L60
    |         |--Entalina Monterosato 1872 GO06, L60 [incl. Eudentalium Cotton & Godfrey 1933 L60]
    |         |    |--*E. tetragona (Brocchi 1814) [=Dentalium tetragonum] L60
    |         |    `--E. quinquangularis L60
    |         |--Bathoxiphus Pilsbry & Sharp 1897 MG-H11, L60
    |         |    |--*B. ensiculus (Jeffreys 1877) [=Dentalium ensiculus] L60
    |         |    `--B. colmani (Palmer 1974) MG-H11
    |         `--Gadila Gray 1847 MG-H11, L60 [incl. Helonyx Stimpson 1865 L60, Loxoporus Jeffreys 1883 L60; Gadilinae]
    |              |--*G. gadus (Montagu 1803) [=Dentalium gadus, Cadulus (*Gadila) gadus] L60
    |              |--G. braziliensis (Henderson 1920) S11
    |              `--G. tolmiei SW11
    `--Dentalioida [Dentalida] PR79
         |--Dentaliidae MG-H11
         |    |--Dentalium GO06
         |    |--Prodentalium Young 1942 L60
         |    |    `--*P. raymondi Young 1942 L60
         |    |--Plagioglypta Pilsbry & Sharp 1897 L60
         |    |    |--*P. undulata (Münster 1844) [=Dentalium undulatum] L60
         |    |    `--P. iowaensis [=Coleolus iowaensis] PR79
         |    `--Fissidentalium Fischer 1885 MG-H11, DK08 [incl. Schizodentalium Sowerby 1894 L60]
         |         |--*F. ergasticum Fischer 1885 [=Dentalium (*Fissidentalium) ergasticum] L60
         |         |--F. mawsoni (Ludbrook 1956) [=Dentalium (Fissidentalium) mawsoni] DK08
         |         |--F. shirleyae Lamprell & Healy 1998 MG-H11
         |         `--F. zelandicum (Sowerby 1860) P61
         `--+--Fustiaria Stoliczka 1868 GO06, L60 [Fustiariidae]
            |    |--*F. circinata (Sowerby 1823) [=Dentalium circinatum] L60
            |    `--F. rubescens GO06
            `--+--Antalis Adams & Adams 1854 GO06, L60 (see below for synonymy)
               |    |--*A. entalis (Linnaeus 1758) [=Dentalium entalis] L60
               |    |--A. diarrhox (Watson 1879) [=Dentalium (Antalis) diarrhox] P61
               |    |--A. glaucarena (Dell 1953) [=Dentalium (Antalis) glaucarena] P61
               |    |--A. nana (Hutton 1873) (see below for synonymy) P61
               |    |--A. pilsbryi GO06
               |    |--A. suteri (Emerson 1954) [=Dentalium (Antalis) suteri; incl. D. arenarium Suter 1907] P61
               |    `--A. vulgaris GR98
               `--Laevidentalidae PR79
                    |--Pseudantalis Monterosato 1884 PR79, L60
                    |    `--*P. rubescens (Deshayes 1825) [=Dentalium rubescens] L60
                    |--Rhabdus Pilsbry & Sharp 1897 GO06, L60
                    |    `--*R. rectius (Carpenter 1865) [=Dentalium rectius] L60
                    |--Rhytiodentalium Pojeta & Runnegar 1979 PR79
                    |    `--*R. kentuckyensis Pojeta & Runnegar 1979 PR79
                    `--Laevidentalium Cossmann 1888 MG-H11, S98
                         |--*L. incertum (Deshayes 1825) [=Dentalium incertum] S98
                         |--L. arnoldi Lamprell & Healy 1998 MG-H11
                         |--L. ecostatum (Kirk 1880) [=Dentalium (Laevidentalium) ecostatum] P61
                         |--L. longitrorsum (Reeve 1842) MG-H11
                         `--L. morganianum (Wilckens 1922) [=Dentalium (Laevidentalium) morganianum] F27

Antalis Adams & Adams 1854 GO06, L60 [incl. Entaliopsis Newton & Harris 1894 L60, Entalis Gray 1847 non Sowerby 1839 L60; Antalinae]

Antalis nana (Hutton 1873) [=Dentalium (Antalis) nanum; incl. D. huttoni Kirk 1880, D. marwicki Mestayer 1926] P61

*Type species of generic name indicated

REFERENCES

[DK08] Darragh, T. A., & G. W. Kendrick. 2008. Silicified Eocene molluscs from the Lower Murchison district, Southern Carnarvon Basin, Western Australia. Records of the Western Australian Museum 24 (3): 217–246.

[F27] Finlay, H. J. 1927. A further commentary on New Zealand molluscan systematics. Transactions and Proceedings of the New Zealand Institute 57: 320–485.

[GO06] Giribet, G., A. Okusu, A. R. Lindgren, S. W. Huff, M. Schrödl & M. K. Nishiguchi. 2006. Evidence for a clade composed of molluscs with serially repeated structures: monoplacophorans are related to chitons. Proceedings of the National Academy of Sciences of the USA 103 (20): 7723–7728.

[GR98] Giribet, G., & C. Ribera. 1998. The position of arthropods in the animal kingdom: a search for a reliable outgroup for internal arthropod phylogeny. Molecular Phylogenetics and Evolution 9: 481–488.

[L60] Ludbrook, N. H. 1960. Scaphopoda. In: Moore, R. C. (ed.) Treatise on Invertebrate Paleontology pt I. Mollusca 1: Mollusca—General Features, Scaphopoda, Amphineura, Monoplacophora, Gastropoda—General Features, Archaeogastropoda and some (mainly Paleozoic) Caenogastropoda and Opisthobranchia pp. I37–I41. Geological Society of America, and University of Kansas Press.

[MG-H11] McEnnulty, F. R., K. L. Gowlett-Holmes, A. Williams, F. Althaus, J. Fromont, G. C. B. Poore, T. D. O’Hara, L. Marsh, P. Kott, S. Slack-Smith, P. Alderslade & M. V. Kitahara. 2011. The deepwater megabenthic invertebrates on the western continental margin of Australia (100–1100 m depths): composition, distribution and novelty. Records of the Western Australian Museum Supplement 80: 1–191.

[PR79] Pojeta, J., Jr & B. Runnegar. 1979. Rhytiodentalium kentuckyensis, a new genus and new species of Ordovician scaphopod, and the early history of scaphopod mollusks. Journal of Paleontology 53 (3): 530–541.

[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.

[SW11] Smith, S. A., N. G. Wilson, F. E. Goetz, C. Feehery, S. C. S. Andrade, G. W. Rouse, G. Giribet & C. W. Dunn. 2011. Resolving the evolutionary relationships of molluscs with phylogenomic tools. Nature 480: 364–367.

[S98] Stilwell, J. D. 1998. Late Cretaceous Mollusca from the Chatham Islands, New Zealand. Alcheringa 22 (1): 29–85.

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