A rare species of giant tortoise was feared extinct after over 100 years without any sightings on the Galápagos Islands. But now, officials say they've found one.

An adult female Fernandina Giant Tortoise, or Chelonoidis phantasticus, possibly older than 100, was found on Fernandina Island, Ecuador's Ministry of the Environment said in a statement Wednesday.

The species is unique to Fernandina Island, one of the more than a dozen islands in the famous archipelago known for its biodiversity that helped fuel Charles Darwin's theory of evolution in the 1800s.

Officials with the Giant Tortoise Restoration Initiative, a collaboration between the Galápagos National Park Directorate and Galápagos Conservancy, a U.S. non-profit dedicated to conservation on the islands, and Animal Planet's "Extinct or Alive" series said they made the discovery Sunday.

The animal was found in good health but underweight and was transported to a breeding center on Santa Cruz Island. Genetic tests will be needed to confirm officials' belief that the tortoise is of the species unique to Fernandina, the environment ministry said.

"This encourages us to strengthen our search plans to find other turtles, which will allow us to start a breeding program in captivity to recover this species," said Danny Rueda, director of the Galápagos National Park.

Officials also said it's possible more individuals of the species are still alive.

Biologist Forrest Galante, host of the Animal Planet show which funded the expedition, called it one of the biggest discoveries on the islands in the last 100 years.

"As a biologist and someone who has dedicated my life to the pursuit of animals believed extinct, this is by far my greatest scientific accomplishment and proudest moment," he said in a statement.

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The rare tortoise species was believed to have been threatened by lava flows on the volcanic island, according to the International Union for Conservation of Nature's Red List of Threatened Species.

The last confirmed sighting was in 1906, but signs that the species may still be alive had been found since, giving researchers hope.

In 1964, large tortoise scats and bite marks on a cactus were spotted and, in 2013, scat and footprints were found, according to the IUCN Red List, the comprehensive list of engendered species around the globe. An unconfirmed sighting may have occurred in 2009, the organization also says.

The species had been officially listed as "Critically Endangered (Possibly Extinct)" under the Red List's classifications.

Named for their giant tortoises, the Galápagos Islands was home to many unique species of the reptiles. Human exploitation and threats from invasive species have endangered some species and caused others to go extinct, according to the Galápagos Conservancy.

Today, only two groups of giant tortoises remain around the world – those on the Galápagos Islands in the Pacific Ocean and others on Aldabra Atoll in the Indian Ocean, the Galápagos Conservancy says.

The Galápagos Islands, a UNESCO World Heritage Site, are part of Ecuador and roughly 600 miles off its coast.

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