Species that have moved towards oblivion include the Yangtze river dolphin, now officially described as "critically endangered (possibly extinct)", as well as Africa's lowland gorillas, Asian vultures, Pacific corals and numerous North American reptiles.

In an update of its famous Red List, the Swiss-based IUCN said it had identified 41,415 species at threat. Of this 16,306 species, equivalent to 39 percent of the total, are in danger of extinction, 188 more than last year.

"The invaluable efforts made so far to protect species are not enough," said IUCN Director-General Julia Marton-Lefevre.

"The rate of biodiversity loss is increasing and we need to act now to significantly reduce it and stave off this global extinction crisis."

The Red List is one of the most authoritative markers of biodiversity.

It is compiled by conservationists, who apply strict criteria to evaluate sightings of the species and the state of its habitat.

Threat risk is graded according to a descending order of categories: "Extinct, or Extinct in the Wild"; "Critically Endangered, Endangered and Vulnerable," applying to degrees of threats of global extinction; "Near Threatened"; "Least Concern," meaning that there is a low risk of extinction; and "Data Deficient", meaning that information is lacking to make an assessment.

One in four mammals, one in eight birds, a third of amphibians and 70 percent of the world's assess plants are in jeopardy, the IUCN said.

The new Red List, unveiled in Paris, placed the spotlight on these species:

-- The Yangtze river dolphin, or baiji (Lipotes vexillifer), hit by pollution, fishing, river traffic and habitat destruction.

A long search for this Chinese mammal last November and December proved fruitless, causing it be listed as possibly extinct.

Confirmation of its extinction can only be made when further surveys are carried out; a possibly sighting of the creature, reported last month, is being investigated by Chinese scientists, the IUCN said.

-- The western gorilla (Gorilla gorilla), which moves from Endangered to Critically Endangered. Researchers have uncovered a sudden fall in numbers of the main subspecies, the western lowland gorilla, decimated by the bushmeat trade and Ebola virus.

-- African and Asian vultures, five species of which have moved categories. They include Asia's red-headed vulture (Sarcogyps calvus), which moves from Near Threatened to Critically Endangered, its decline driven by fatal ingestion of the drug diclofenac, used to treat injured livestock.

-- Reptiles: In an exceptional move, the IUCN decided to add 723 turtles, snakes and other North American and Mexican reptiles to the Red List.

They include a Mexican freshwater turtle called the Cuatro Cienegas slider (Trachemys taylori), endangered by habitat loss, and the Santa Catalina Island rattlesnake (Crotalus catalinensis), persecuted by illegal collectors.

-- The Banggai cardinalfish (Pterapogon kauderni), a species that is only found near the Banggai islands near Sulawesi, Indonesia. The fish enters the Red List for the first time, listed as Endangered. Demand from the aquarium trade means that 900,000 of these fish are being hauled out of the sea each year.

Only one species has moved to a lower category of threat: the Mauritius echo parakeet (Psittacula eques).

Fifteen years ago, it was one of the world's rarest parrots; this year, though, it has moved Critically Endangered to Endangered.

"The improvement is a result of successful conservation action, including close monitoring of nesting sites and supplementary feeding, combined with a captive breeding and release programme," the IUCN said.

The IUCN said that the total number of extinct species stands at 785, and further 65 are only found in captivity or in cultivation.

Estimates of the world's biodiversity vary between 10 and 100 million species, with 15 million the most commonly-cited figure. Only 1.7 million species have been described.

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