The species is also known as Chelonoidis phantasticus, and is thought to have become extinct more than a century ago. The discovery was made through a joint venture between the Galapagos National Park and the US-based Galapagos Conservancy. Washington Tapia of Galapagos Conservancy, a non-profit organisation dedicated to conserving the Galapagos said the tortoise is “very old” and “exceeds 100 years” in age.
Ecuador’s Environment Minister Marcelo Mata confirmed the news through a statement on Twitter.
He said a “specimen (adult female) turtle species Chelonoidis Phantasticus, thought to be extinct more than 100 years ago” was found on the island.
Conservationists were hopeful other members of the species were on the island, because of tracks and faeces they found.
The tortoise has been taken to a breeding centre for giant tortoises on Santa Cruz Island, where it will stay in a specially designed pen.
Genetic tests will be carried out to confirm the tortoise was in fact a member of the long-lost species.
Stuart Pimm, a professor of conservation ecology at Duke University, said: “They will need more than one, but females may store sperm for a long time. “There may be hope.”
The International Union for Conservation of Nature has listed the Fernandina Giant Tortoise as critically endangered and possibly extinct.
The only other living member of the species was found in 1906.
Since then several expeditions have found tortoise faeces and bite marks on cacti and there was a possible unconfirmed sighting in 2009.
However the discovery on Sunday was the first confirmed sighting and it raised the possibility of finding more members of the rare species.
There were fears the species became separate from one another by frequent volcanic lava flows that cover the island.
The Chelonoidis phantasticus species is native to Fernandina, which is uninhabited.
Fernandina is the third largest Galapagos island and features the La Cumbre volcano, which is one of the most active in the world.
The archipelago lies in the Pacific Ocean about 620 miles (1,000km) off Ecuador’s mainland.
The Galapagos archipelago hosts unique species and wildlife whose characterises helped Charles Darwin develop his theory of evolution.
It was declared a Unesco world heritage site in 1979.