Aaadonta irregularis


Taxonomy [top]

Kingdom Phylum Class Order Family

Scientific Name: Aaadonta irregularis
Species Authority: Semper, 1874
Endodonta irregularis Semper, 1874
Helix (Endodonta) irregularis (Semper, 1874)

Assessment Information [top]

Red List Category & Criteria: Critically Endangered B2ab(ii,iii) ver 3.1
Year Published: 2012
Date Assessed: 2011-08-22
Assessor(s): Rundell, R.J.
Reviewer(s): Cowie, R., Barker, G., Triantis, K. & GarcĂ­a, N.
Facilitator/Compiler(s): Pippard, H.

This is a minute ground-dwelling snail endemic to Palau. The species was previously known only from Peleliu, where type material was collected in the late 19th century and seven specimens were collected at multiple localities in 1936. However, no specimens were found on this island during surveys in 2003. The only recent collections of this species are two live shells that were found at a single locality (1 location) on Omekang island in 2007. The species is assessed as Critically Endangered, based on the limited area of occupancy, the single location, the very small number of specimens that have been recently found (despite surveys of available native habitat) and the known decline in the area and quality of its habitat.

1996 Data Deficient

Geographic Range [top]

Range Description:

The type locality for this species is Peleliu (Beliliou) island in Palau. The historical geographic range of of the species is estimated to be less than 12 km2. The species was probably historically more abundant prior to its collection at several localities in 1936. Indeed, substantial change had already occurred on that island by that time. The present area of occupancy of this species is estimated at less than 0.5 km2, since only two live specimens have been found recently (2007) at a single locality on the very small island of Omekang (Rundell 2007, unpublished data).

Range Map:Click here to open the map viewer and explore range.

Population [top]

Population: The type locality for this species is Peleliu (Beliliou) island in Palau, where type material was collected in the late 19th century and seven specimens were collected at multiple localities in 1936 by Y. Kondo (Solem 1976). However, no specimens were found during surveys of Peleliu in 2003 (Rundell 2003, unpublished data, Rundell 2005 and 2010). A decline in the population of this species is inferred from the known decline of the extent and quality of its habitat.
Population Trend: Decreasing

Habitat and Ecology [top]

Habitat and Ecology: This species has been recorded in tropical moist lowland forest.
Systems: Terrestrial

Use and Trade [top]

Use and Trade: This species is not utilized.

Threats [top]

Major Threat(s):

This species is threatened by destruction and modification of native lowland forest. Therefore it is not surprising that the species has probably been extirpated from the highly modified island of Peleliu, whose forest was burned in World War II with flamethrowers (Hinz 1995, Crombie and Pregill 1999). Disruption of the ground, rocks and leaf litter may be of particular significance to this and other endodontid species. Endodontoid land snails are among the most threatened land snails on Pacific Islands in the few places where they still exist (Solem 1983), and therefore the fact that this species is still extant is important. This species is in need of conservation attention.

Conservation Actions [top]

Conservation Actions:

Field work to define the current distribution of this species as well as research on its population status and trends, identification and protection of priority sites for species conservation such as key biodiversity areas (including threatened land snails) and reducing the impacts of human activities, especially on the small islands of the archipelago, is urgently needed. The Palau Conservation Society has been supportive of recent land snail survey work in Palau.

Bibliography [top]

Crombie, R.I. and Pregill, G.K. 1999. A checklist of the herpetofauna of the Palau Islands (Republic of Belau), Oceania. Herpetological Monographs 13: 29-80.

Hinz, E. 1995. Pacific Island Battlegrounds of World War II: Then and Now. The Bess Press, Honolulu.

IUCN. 2012. IUCN Red List of Threatened Species (ver. 2012.2). Available at: (Accessed: 17 October 2012).

Rundell, RJ. 2005. The land snails of Belau: Survey of the 16 states.

Rundell, RJ. 2008. Cryptic diversity, molecular phylogeny and biogeography of the rock- and leaf litter-dwelling land snails of Belau (Republic of Palau, Oceania). Philosophical Transactions of the Royal Society of London B 363: 3401-3412.

Rundell, RJ. 2010. Diversity and conservation of the land snail fauna of the western Pacific islands of Belau (Republic of Palau, Oceania). American Malacological Bulletin 28: 81-90.

Semper, C. 1874. Landmollusken. Reisen im Archipel der Philippinen 2(3): 129-168.

Solem, A. 1976. Endodontoid land snails from Pacific islands (Mollusca: Pulmonata: Sigmurethra). Part I. Family Endodontidae. Field Museum of Natural History, Chicago.

Solem, A. 1983. Endodontoid land snails from Pacific islands (Mollusca: Pulmonata: Sigmurethra). Part II. Families Punctidae and Charopidae. Zoogeography. Field Museum of Natural History, Chicago.

Citation: Rundell, R.J. 2012. Aaadonta irregularis. In: The IUCN Red List of Threatened Species. Version 2015.2. <>. Downloaded on 30 August 2015.
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