IUCN SSC Mid-Atlantic Island Invertebrates Specialist Group


BackChilonopsis nonpareil (Perry, 1811)

Chilonopsis nonpareil (Perry, 1811)

Great Saint Helena Awl Snail (English)

  • Kingdom: Animalia
  • Phylum:
  • Class: Mollusca
  • Order: Gastropoda
  • Family: Subulinidae
EX Extinct
IUCN Red List Status:

Countries of Occurrence:
Saint Helena - British Overseas Territory

St. Helena

Pryce, D. & White, L.

Gerlach, J.


Facilitators / Compilers/s:

Assessment Rationale:

This species has not been seen alive since pre-1875 with only sub-fossil shells now being found. This was a large species with a shell up to 50 mm long; it is now considered Extinct.

Geographic Range:

This species was endemic to the island of St Helena, in the South Atlantic Ocean, where it is now considered extinct. As the species is known entirely from a few sub-fossil shells it is not possible to produce a range map for this species

Portugal - Azores
Extent of Occurrence (EOO):
Area of Occupancy (AOO):
Elevation Lower Limit:
Elevation Upper Limit:
Biogeographic Realms:
South Atlantic Ocean
Endemic St. Helena


When writing his book on the natural history of the island Melliss (1875) called this "The great extinct Land Snail of St. Helena". At the time of writing there were still people who recalled seeing the species alive and indeed a few who still claimed it to be present; Melliss was very keen to find the species and explored the area it had last been seen very thoroughly but failed to locate it. The species may well have gone extinct pre-1875 due to habitat degradation from alien invasive plant and animal species. The shell is very thick and these can still occasionally be found as sub-fossils

Habitat and Ecology

The species seems to have been present in the drier parts of the island and was known from the Sugarloaf Ridge area; a sub-fossil shell has recently been found near Bencoolen. As no live specimen has ever been seen it is not possible to speculate on the precise habitat or ecology of this species

Major Threat(s):

A live specimen of this species has never been found; the only records are pre-1875 and are of sub-fossil shells. While there is no documentary evidence on the causes of decline it is probable that this species was severely impacted by extensive habitat modification by goats, pigs and rabbits; while the goats and pigs have been removed rabbits are still present. It is also possible that direct predation by invasive non-native species such as rats, mice and the large, aggressive centipede Scolopendra morsitans Linnaeus, 1758 added to the pressure on this species

Conservation Actions

This species is considered to have become extinct pre-1875, therefore, there are no past, current or future conservation actions in place. However, isotope analysis of sub-fossil shells would prove useful to ascertain potential environmental preferences. It is not recommended that any further survey work be undertaken for this species