The freshwater gastropod mollusk has already made its salty tearful goodbyes in the last two years, joining the long-departed Dodo bird among the ranks of vanished creatures.
There are 11,167 other plants and animals threatened with extinction, according to the World Conservation Union's 2002 Red List of Threatened Species, an increase of 121 since 2000.
The Red List, produced by a network of some 7,000 species experts working in almost every country in the world, found that 811 species have disappeared over the last 500 years, some permanently, while others exist only in artificial settings, such as zoos.
Five species have been added to the Extinct List over the last two years, said the union, known as IUCN, which is based in Gland, Switzerland.
Besides the mollusk they include two hippo species, last seen in 1500, the sea mink, unseen since 1860, and Reunion Island sheldgeese, last sighted around 1710.
"It can take so long because we need scientific proof and records that the species has gone extinct and that there are no subspecies alive," said IUCN spokeswoman Xenya Cherny. "That can take a long time."
The group has examined some 18,000 species and subspecies around the globe. But scientists admit that even a study of this magnitude only scratches the surface. Earth is home to an estimated 14 million species - and only 1.75 million have been documented.
Many may become extinct before they are even identified, much less studied by scientists.
Conservationists think the current extinction rate is 1,000 to 10,000 times higher than it should be under natural conditions. That means that in the first decades of the 21st century, many creatures may disappear.
The primary reason: humans. Everything from expanding cities to deforestation, agriculture and fishing pose a significant threat to the planet's biodiversity, IUCN says.
The Saiga antelope, which lives on the open dry steppe grasslands and semiarid deserts of Central Asia, the wild Bactrian camel, which generally inhabits China, the Ethiopian water mouse and the Iberian lynx have all been upgraded to critically endangered, the closest to extinction, the report said.
Surprisingly, two species previously considered extinct have been rediscovered, the Lord Howe Island stick insect and the Bavarian pine vole. The stick insect was believed to have become extinct in 1920 but was seen again in 2001. No specimens of the Bavarian pine vole were recorded after 1962 but a small population of the rodents was found on the German-Austrian border in 2000.
The number of endangered primate species rose from 120 to 195 over the past two years. Nearly half are native to Asia. Five of the rarest species are found in Vietnam; only some 100 individuals of the golden-headed langur live on the country's Cat Ba Island.
"Vietnam is at risk of undergoing a major primate extinction spasm within the next few years if rapid action is not taken," said Conservation International president Russ Mittermier, whose group contributed data to the red list study.
The study found habitat loss and degradation affect 89 percent of all threatened birds, 83 percent of mammals and 91 percent of threatened plants assessed. Lowland and mountain tropical forests were the habitats with the highest number of threatened mammals and birds.
The IUCN has collected data on endangered species for 37 years.
"On the Red List, all species are treated with equal importance - the humble Bavarian pine vole stands alongside the African rhino," said IUCN Director General Achim Steiner. "It provides the international benchmark to help guide effective biodiversity conservation."
By Erica Bulman