Norfolk Island: Land Snails

Overview

Norfolk Island, despite an area of just 35 square kilometres, has a high diversity of endemic land snails, when compared to other small islands. There are around 70 described species, although it is thought that this number may have been overestimated and that the true number of unique species is probably closer to 60. Land clearing, combined with the introduction of Polynesian Rats around 1,000 years ago, and Black Rats during the middle of the 20th century, as well as predation by mice and chickens, has likely reduced the number of surviving species to around 50, with five species considered critically endangered.

The endemic land snails of Norfolk Island range in shell diameter from just one millimetre to 22 millimetres, across a wide range of shell shapes. While most species were once widespread across the island, many are now mostly restricted to Norfolk Island National Park, the only area of remnant subtropical rainforest on the island.

In 2020, scientists from the Australian Museum surveyed land snails on Norfolk Island for the first time in almost 20 years , discovering a population of Advena campbelli, a species that is currently listed as Extinct on the IUCN Red List and as Critically Endangered by the Australian Government. The museum has also, this year, commenced a captive breeding program involving some Norfolk Island land snail species, in conjunction with Taronga Zoo, Parks Australia and the Norfolk Island Regional Council.

Technical specifications

Issue date: 22 June 2021
Issue withdrawal date: 31 December 2021
Denomination: $1.10 x 1, $2.20 x 1
Stamp illustration: Janet Matthews
Stamp & product design: Simone Sakinofsky, Australia Post Design Studio
Paper: gummed: Tullis Russell
Printer: Ego
Printing process: Offset lithography
Stamp size (mm): 37.5 x 26
Minisheet size (mm): 135 x 80
Perforations: 13.86 x 14.6
Sheet layout: Module of 50
FDI Postmark: Norfolk Island NSW 2899
FDI withdrawal date: 21 July 2021

Stamps in this issue

$1.10 Greenwoodoconcha nux

Greenwoodoconcha nux has a small, thin and shiny shell that is rich, dark red-brown in colour, often with a broad, white peripheral band. It has microscopic spiral linear grooves on its seven-millimetre surface area, these grooves being typical of species in the Microcystidae family. It is found in mixed leaf forest at Rocky Point Reserve and Norfolk Island National Park, where it lives in leaf litter, under fallen palm leaves and under bark on logs. Stamp illustration is by wildlife artist Janet Matthews.

$2.20 Duritropis albocarinata

Eastern Australian snails from the Assimineid family are confined to Norfolk Island and Lord Howe Island. The Assimineid Duritropis albocarinata (also known as Omphalotropis albocarinata and Omphalotropsis brenchleyi) has a small shell of around six millimetres, with wavy ribs and swirls. Its shell ranges in colour from yellow and orange to red and purple-brown, and there is often one to several coloured bands around the periphery, which is common for Norfolk Island assimineids. This species is found at Mount Bates, Mount Pitt, Rocky Point Reserve, Cemetery Bay and Duncombe Bay, where it grazes on logs, endemic plants and wet leaf litter within rainforests and woodlands and hides away during dry weather. Stamp illustration is by wildlife artist Janet Matthews.