Belongs within: Hypsogastropoda.
Contains: Struthiolaria, Aporrhaidae, Xenophoridae, Strombidae.
The Stromboidea are a group of often large marine gastropods that exhibit determinate growth with the shell often becoming elaborated around the aperture. In life, stromboids have a characteristic ‘hopping’ mode of locomotion is which the animal is raised on the muscular column of the foot, using the claw-like operculum as an anchor. The Struthiolariidae, ostrich foots, live buried in sand and draw water over the gills to filter out plankton.
The life of an ostrich foot
Published 3 March 2008
The Struthiolariidae are a family of marine gastropods (specifically caenogastropods, a large clade characterised by the possession of a feeding proboscis) commonly known as “ostrich foot shells”. I have to confess complete ignorance as to why they are supposed to resemble an ostrich’s foot. If you look at the photos above of Struthiolaria papulosa (from gastropods.com), I suppose you might be able to see a resemblance if you exercise a significant amount of imagination, but I doubt it would be the first thing I would think of.
Ostrich foot shells are an entirely Southern Hemisphere family, found in cooler waters. Despite a fossil record extending back to the Cretaceous, the Struthiolariidae is currently not a very speciose family—gastropods.com lists only seven species. New Zealand is the current centre of diversity (four species), and also the source of the oldest known fossil struthiolariids of the genus Conchothyra. A single species is known from Australia, one from South Georgia, and one from South Georgia and Kerguelen. Struthiolariids can reach a respectable size—Struthiolaria papulosa can be nearly 9 cm long. The thickened lip that can be seen around the shell opening in the photo above is considerably stronger than the rest of the shell, and often remains intact long after the remainder has worn away—they are a common find on sandy New Zealand beaches.
Struthiolariids show two major modes of movement. They may crawl about on the foot like most gastropods, or they may use a more dramatic mode of movement in which fluid is drawn from the foot and the small operculum (visible in the photo at the top) is directed downwards. The operculum ends in a sharp hook, and this is used to push against the sediment and lunge the animal forward in a clumsy leap (in the related Strombidae, the conches, the sole of the foot has become permanently reduced and this second method is their only way of moving). This opercular movement can also be used to right the animal when it becomes tipped upside-down. Crump (1968) recorded that opercular movement was used when the animal came in touch with a sea star to throw itself into a series of rapid somersaults to carry itself away from the potential predator. Morton (1951) also suggested a defensive function for the operculum—when a live specimen was held away from the substrate, the operculum would be extended out in an attempt to gain a purchase. Even if this was primarily the usual righting action, the sharp, hooked operculum being waved about could quite possibly deter a potential predator.
Despite being quite capable of moving about, struthiolariids are actually sessile filter-feeders by habit. The above figure from Morton (1951) shows a specimen of Struthiolaria papulosa buried beneath the sand in feeding position. The animal digs itself into the sand using its foot, and the long proboscis is used to construct two mucus-lined tubes that house the inhalent and exhalent siphons. A continuous stream of water and particulate matter is taken in through the inhalent siphon, filtered through the mucus-producing endostyle and the gills, and the filtered water is expelled through the exhalent siphon while the particulate matter is trapped in a string of mucus and carried along a specialised food grove to the front of the animal, where it can be ingested through the proboscis.
The gastropod family most closely related to the Struthiolariidae, the pelican’s foot shells of the Aporrhaidae, share the characters of the paired siphons and infaunal living habit. However, the aporrhaids do not have the gills specialised into feeding structures as in the struthiolariids. Instead, the aporrhaids use the strong current produced the movement of water over the gills to draw particulate matter towards the front of the animal, where it is picked up by the proboscis in the normal caenogastropod fashion. In 1937, before the lifestyle of the Struthiolariidae had ever been investigated, Yonge suggested that the mode of feeding found in Aporrhaidae was a possible precursor to ciliary feeding as found in many mollusc groups. It therefore came as significant support to Yonge’s speculations when the exact development in feeding mode he had suggested was discovered by Morton (1951) in the aporrhaids’ closest relatives.
Systematics of Stromboidea
Characters (Simone 2011): Shell fusiform with determinated growth. Incurrent shell canal. Enlargmement of distance between head base and furrow of pedal gland. Septum separating haemocoel from visceral cavity muscular constituted. Terminal nucleus of operculum. Pallial tentacle in front of anus. Reversion to a thick hypobranchial glans. Loss of pair of longitudinal folds in middle esophagus. Bursa copulatrix of females situated in anterior region of pallial oviduct, originating from genital pore. Females with furrow running in the right side of the head-foot, originating from genital pore.
<==Stromboidea [Leptopoda, Strombacea, Strombimorpha, Xenophoracea]
|--Struthiolariidae [Struthiolariinae, Struthiolarinae]S11
| |--PerissodontaKB99
| |--StruthiolariaBR17
| |--Struthiolarella Steinman & Wilckens 1908 [Struthiolarellinae]BR05
| | `--*S. ameghinoi (Ihering 1899) [=Struthiolaria ameghinoi]BR17
| |--Monalaria Marwick 1926F26
| | `--*M. concinna [=Struthiolaria tuberculata concinna]F26
| `--TylospiraS11
| |--T. coronataBRW98
| `--T. scutulata (Gmelin 1791)S11
`--+--Cuphosolenus serresianus (Michaud 1828)S11
`--+--AporrhaidaeS11
`--+--XenophoroideaBR17
| |--XenophoridaeS11
| `--Lamelliphorus Cossmann 1916BR05 [LamelliphoridaeBR17]
| |--*L. ornatissimus (d’Orbigny 1850) [=Trochus ornatissimus]BR17
| |--L. supraliasinus (Vacek 1886)TTE93
| `--L. tortilis (Peron 1900)TTE93
`--+--StrombidaeS11
`--SeraphsidaeBR17
|--Seraphs Montfort 1810 [=Seraphys (l. c.); Seraphina, Seraphsinae, Seraphyinae]BR05
| |--*S. convolutum (Lamarck 1802) [=Terebellum convolutum]BR17
| `--S. sopitus (Solander in Brander 1766)TTE93
`--Terebellum Lamarck 1798S11, BR05 (see below for synonymy)
|--*T. terebellum (Linnaeus 1758)BR17 [=Bulla terebellumBR17, Conus terebellumH09]
|--T. fusiformeL10
`--T. subulatum Lamarck 1810L10 (see below for synonymy)
Stromboidea incertae sedis:
Thersitea Coquand 1862 [Thersiteidae]BR05
|--*T. gracilis Coquand 1862BR17
`--T. ponderosa (Coquand 1862)TTE93
Oncoma Mayer 1876 [=Dilatilabrum Cossmann 1904; Dilatilabridae]BR17
|--*O. meneguzzoi (Mayer 1876) [=Strombus meneguzzoi, *Dilatilabrum meneguzzoi]BR17
`--‘Strombus (Dilatilabrum)’ fortisi Brongniart 1823 [incl. S. fortisi var. valdetuberculatus]A60
HippochrenidaeBR17
|--Hippochrenes Montfort 1810 [Hippochreninae]BR17
| `--*H. macropterus (Lamarck 1803) [=Rostellaria macroptera]BR17
`--Wateletia Cossmann 1889 [Wateletiinae, Wateletinae]BR17
`--*W. geoffroyi (Watelet 1855) [=Rostellaria geoffroyi]BR17
RostellariidaeBR17
|--Calyptraphorus Conrad 1857 [Calyptraphorinae]BR17
| |--*C. velatus (Conrad 1857) [=Rostellaria velata]BR17
| |--C. indicus Cossmann & Pissarro 1909MP14
| `--C. palliatus (Forbes 1848)TTE93
|--Rimella Agassiz 1841 non Raf. 1819 (ICBN)BR05 [Rimellidae, RimellinaeBR17]
| |--*R. fissurella (Linnaeus 1767)BR17 [=Strombus fissurellaBR17, Rostellaria fissurellaW93]
| |--R. cancellata Lamarck 1816WG71
| |--R. crispata (Sowerby 1842)W93
| `--R. javana Martin 1879 [incl. Cancellaria neavolutella Noetling 1901]PH90
`--Tibia Röding 1798 [=Rostellaria Lamarck 1799; Rostellariinae, Rostellarinae, Tibiidae]BR05
|--*T. fusus (Linnaeus 1758) (see below for synonymy)BR17
|--‘Rostellaria’ crebricostata Zekeli 1852 (see below for synonymy)F27b
|--‘Rostellaria’ curta Sowerby 1842S42
|--‘Rostellaria’ curvirostrumS42
|--T. insulaechorab Röding 1798S11
`--T. powisiW93
Pereiraea Crosse 1867 [Pereiraeidae]BR17
`--*P. gervaisii (Vézian 1856) [=Pleurotoma gervaisii]BR17
Cassianozyga Bandel 1991B91
`--*C. seelandica Bandel 1991B91
Hemizyga Girty 1915B91, HS80 [incl. Strianematina Chronic 1952KC60]
|--*H. elegans Girty 1915KC60
|--H. decussata Yoo 1988B91
|--H. dubiaHS80
|--H. grandicostataHS80
`--H. graniferaBRW98
‘Rostellaria’ crebricostata Zekeli 1852 [incl. Mitra cancellata Sow. 1832 nec Bolten 1798 nec Swainson 1821, Voluta cristata Zekeli 1852]F27
Terebellum Lamarck 1798S11, BR05 [=Terebrina Rafinesque 1815W93; incl. Artopoia Gistel 1848W93, Lucis Gistel 1848W93; TerebellinaeBR05]
Terebellum subulatum Lamarck 1810L10 [=*Artopoia subulataW93, *Lucis subulatusW93; incl. Bulla sopitaL10, B. volutataL10]
*Tibia fusus (Linnaeus 1758) [=Murex fusus, *Rostellaria fusus, Strombus fusus; incl. Tibia indiarum Röding 1798]BR17
*Type species of generic name indicated
References
[A60] Abbott, R. T. 1960. The genus Strombus in the Indo-Pacific. Indo-Pacific Mollusca 1 (2): 33–146.
[B91] Bandel, K. 1991. Über triassische “Loxonematoidea” und ihre Beziehungen zu rezenten und paläozoischen Schnecken. Paläontologische Zeitschrift 65 (3–4): 239–268.
[BRW98] Beesley, P. L., G. J. B. Ross & A. Wells (eds) 1998. Fauna of Australia vol. 5. Mollusca: The Southern Synthesis. Part A. Australian Biological Resources Study: Canberra.
[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.
Crump, R. G. 1968. The flight response in Struthiolaria papulosa gigas Sowerby. New Zealand Journal of Marine and Freshwater Research 2: 390–397.
[F26] Finlay, H. J. 1926. A further commentary on New Zealand molluscan systematics. Transactions and Proceedings of the New Zealand Institute 57: 320–485.
[F27] Finlay, H. J. 1927. New specific names for austral Mollusca. Transactions and Proceedings of the New Zealand Institute 57: 488–533.
[H09] Hedley, C. 1909. The Marine Fauna of Queensland: Address by the President of Section D. Australasian Association for the Advancement of Science: Brisbane.
[HS80] Hoare, R. D., & M. T. Sturgeon. 1980. The Pennsylvanian pseudozygopleurid gastropod genus Gamizyga n. gen. from Ohio and West Virginia. Journal of Paleontology 54 (1): 159–187.
[KB99] Kiel, S., & K. Bandel. 1999. The Pugnellidae, a new stromboidean family (Gastropoda) from the Upper Cretaceous. Paläontologische Zeitschrift 73 (1–2): 47–58.
[KC60] Knight, J. B., L. R. Cox, A. M. Keen, R. L. Batten, E. L. Yochelson & R. Robertson. 1960. Gastropoda: systematic descriptions. 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. I169–I331. Geological Society of America, and University of Kansas Press.
[L10] Lamarck, J.-B. P. A. de M. de. 1810. Suite de la détermination des espèces de mollusques testacés. Annales du Muséum d’Histoire Naturelle 16: 300–328.
[MP14] Merle, D., J.-M. Pacaud, G. Métais, A. Bartolini, R. A. Lashari, I. A. Brohi, S. H. Solangi, L. Marivaux & J.-L. Welcomme. 2014. Volutidae (Mollusca: Gastropoda) of the Lakhra Formation (earliest Eocene, Sindh, Pakistan): systematics, biostratigraphy and paleobiogeography. Zootaxa 3826 (1): 101–138.
Morton, J. E. 1951. The ecology and digestive system of the Struthiolariidae (Gastropoda). Quarterly Journal of Microscopical Science s3-92: 1–25.
[PH90] Petit, R. E., & M. G. Harasewych. 1990. Catalogue of the superfamily Cancellarioidea Forbes and Hanley, 1851 (Gastropoda: Prosobranchia). Nautilus 103 (Suppl. 1): 1–69.
[S11] Simone, L. R. L. 2011. Phylogeny of the Caenogastropoda (Mollusca), based on comparative morphology. Arquivos de Zoologia 42 (4): 161–323.
[S42] Sowerby, G. B., Jr. 1842. On a new species of the genus Rostellaria. Proceedings of the Zoological Society of London 10: 165.
[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.
[W93] Wilson, B. 1993. Australian Marine Shells vol. 1. Prosobranch Gastropods. Part One. Odyssey Publishing: Kallaroo (Western Australia).
[WG71] Wilson, B. R., & K. Gillett. 1971. Australian Shells: illustrating and describing 600 species of marine gastropods found in Australian waters. A. H. & A. W. Reed: Sydney.