Belongs within: Cerithiimorpha.
The Litiopidae are a family of small marine gastropods found in shallow waters on algae and sea-grasses. They are characterised by a high-spired, conical translucent shell, and a long, narrow foot with a median slit in the rear part of the underside, and several epipodial tentacles along the side.
The litiopids: small sea-snails among the weeds
Published 22 February 2017
I may have commented before that biodiversity tends to increase as one moves to a smaller scale. If I haven’t, I certainly should have. The number of small representatives of a group will almost always be greater than the number of large ones. And if one considers the molluscs, for instance, the diversity of large, eye-catching species is considerably smaller is considerably smaller than the diversity of the micro-mollusks that usually go unnoticed.
The Litiopidae are a group of marine gastropods that are found living among and feeding on seaweeds and seagrasses; though little recognised, they can be very abundant. They have high-spired, conical, translucent shells that reach about an inch in length in the largest species, but seem to be more commonly less than a centimetre. They belong among the larger gastropod clade known as the Cerithioidea and can be difficult to distinguish from other members of this clade by their shells alone. Most members of the Litiopidae are placed within the genera Litiopa and Alaba.
The soft anatomy of the family is more distinctive (Houbrick 1987). Litiopids have a long, narrow foot with a median slit in the rear part of the underside marking the opening of a large mesopodial mucous gland. The sides of the foot carry several epipodial tentacles; in other gastropods with such tentacles, they provide a sensory function. A pair of long tentacles is also present on the head, which is produced into an extensible bilobed snout. A pair of small eyes is present at the base of the tentacles.
Litiopids glide about on the underwater vegetation at some speed; they are also able to glide upside-down on the water surface, hanging from the surface tension. The trail of mucus laid down by the mesopodial mucous gland functions like the drag-line laid down by a spider. If the animal finds itself torn away from its substrate, the mucous strand tethers it in place, and it can then haul itself back into place.
Systematics of Litiopidae
<==Litiopidae [Litiopina, Litiopinae] |--Astrolaba Laseron 1956PS10 |--Diffalaba Iredale 1936PS10 | |--*D. opiniosa Iredale 1936PS10 [=Alaba opiniosaW93] | |--D. picta (Adams 1961) [=Astrolaba picta]PS10 | `--D. vladivostokensis (Bartsch 1929) [=Alaba vladivostokensis]PS10 |--Litiopa Rang 1829O27 | |--*L. melanostoma Rang 1829BR17 | |--L. acuminata (Baudon 1856)TTE93 | |--L. bombyx Rang 1829O27 | `--L. limnophysa Melvill & Standen 1896W93 `--Alaba Adams & Adams 1853 (see below for synonymy)W93 |--*A. melaneura [=Rissoa melaneura]W93 |--A. bowenensis (Laseron 1956)K90 [=*Australaba bowenensisW93] |--A. catalinensis Bartsch 1920O27 |--‘*Gibborissoa’ costellataW93 |--A. flammea (Pease 1867) [=Rissoa flammea non Sabanaea flammea Frauenfeld 1867 (not preoc. if in dif. gen.)]H09 |--A. fragilis (Thiele 1930)W93 |--A. incerta (Orbigny 1842)S11 |--A. jeanettae Bartsch 1910O27 |--A. lixa Iredale 1936 [=*Obstopalia lixa]W93 |--A. phasianella Angas 1867H09 |--A. semistriata Philippi 1849H09 |--A. supralirataC64 |--A. terebralisC64 |--A. translucida (Hedley 1905) [=*Dialessa translucida]W93 `--A. trivericosaO27
Alaba Adams & Adams 1853 [incl. Australaba Laseron 1956, Dialessa Iredale 1955, Obstopalia Iredale 1936, Gibborissoa Cossmann in Sacco 1895]W93
*Type species of generic name indicated
References
[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.
[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.
[H09] Hedley, C. 1909. The Marine Fauna of Queensland: Address by the President of Section D. Australasian Association for the Advancement of Science: Brisbane.
Houbrick, R. S. 1987. Anatomy of Alaba and Litiopa (Prosobranchia: Litiopidae): systematic implications. Nautilus 101 (1): 9–18.
[K90] Kendrick, G. W. 1990. A Pleistocene molluscan fauna with Anadara trapezia (Deshayes) (Bivalvia: Arcoida) from the Dampier Limestone of Shark Bay, Western Australia. In: Berry, P. F., S. D. Bradshaw & B. R. Wilson (eds) Research in Shark Bay: Report of the France-Australe Bicentenary Expedition Committee pp. 33–48. Western Australian Museum.
[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).
[PS10] Prozorova, L. A., & T. Y. Sitnikova. 2010. Morphology and systematic implications of juvenile litiopids (Caenogastropoda: Cerithioidea: Litiopidae) from the southern Russian Far East. In: China-Russia Bilateral Symposium: Proceedings of the China-Russia Bilateral Symposium of “Comparison on Marine Biodiversity in the Northwest Pacific Ocean”, 10–11 October 2010, Qingdao (China) pp. 142–145. Institute of Oceanology, Chinese Academy of Sciences; A. V. Zhirmunsky Institute of Marine Biology, Far East Branch of the Russian Academy of Sciences.
[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.
[W93] Wilson, B. 1993. Australian Marine Shells vol. 1. Prosobranch Gastropods. Part One. Odyssey Publishing: Kallaroo (Western Australia).