The “fantastic giant tortoise” — a rare Galápagos species with a huge, flared shell — has only been identified once, more than a century ago, in 1906. It’s since widely been considered extinct.

But that’s not the case, researchers found this week.

Hints that the mysterious species has lived on have arisen over the century — including 1960s reports of tortoise scat on the species’ native Fernandina Island, which is the Galápagos’ youngest, most pristine and most volcanically active island. But anecdotes and rumors were “tenuous at best,” researchers told The Washington Post.

So, a team of conservationists and explorers in 2019 were astonished with a discovery on the rugged island: a lone female giant tortoise. They named her Fernanda.

Although she was the first tortoise discovered on the island since the 1906 spotting, researchers were not sure she was of the same species — Chelonoidis phantasticus, or Fernandina Island tortoise — long thought to be extinct. In fact, many ecologists doubted it.

Fernanda seemed not to be native to Fernandina Island. Perhaps she had floated from a different island, or was taken in a storm, or moved by seafarers, some thought, according to a Princeton University news release.

But by sequencing her entire genome, and setting it next to the historical specimen collected in 1906, researchers this week confirmed that the tortoises, a century apart, were of the same long-considered-extinct lineage: The fantastic giant tortoise — “with a current known population size of a single individual.”

That means she’s considered an “endling,” or the last known individual in a species or subspecies.

Because a species is only declared extinct after exhaustive efforts taken to locate any survivors, “it’s extremely rare for an individual to be found like this — especially after 100 years,” the study’s co-first-author, Stephen Gaughran, told The Post.

There are around 13 other species of Galápagos Island tortoise — all of which descended from the same ancestor. Twelve species are still living, though all are under threat, from vulnerable to critically endangered. One species has long been extinct — and another lineage famously ended in 2012, with the death of endling Lonesome George.

There is an ongoing debate among scientists about whether the Galápagos tortoise groups should be considered subspecies or species; the researchers in this study considered them the latter.

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Galápagos tortoises can grow to over five feet and more than 500 pounds and live for over 100 years. Fernanda is small relative to her species, but she is estimated to be more than 50 years old, possibly due to stunted growth and limited vegetation in her home, the study noted.

When Fernanda was first spotted in 2019, Wacho Tapia, Galápagos-based director of the Giant Tortoise Restoration Initiative, wrote that “the emotional high” he experienced in finding a live tortoise on the remote, seemingly uninhabitable island was “indescribable.”

Upon starting a five-day “mega-expedition” of the difficult-to-explore island of Fernandina, Tapia tempered his expectations, writing that he knew the possibility of finding a tortoise was “near zero” given that no tortoise had been found on the island in 113 years.

But while venturing around, Jeffreys Málaga, a Galápagos National Park Directorate ranger on the expedition, called out “Tortoise!” and Tapia felt “hope and excitement bubble up.”

There, they found Fernanda, relaxing in a spot between some rocks and plants.

She loves eating cactuses, Tapia wrote, and is “healthy and very active” each morning. She is now living at the giant tortoise breeding center of Galápagos National Park.

The island’s volcanic activity led some to fear the worst for the species — “those rugged conditions are likely what made it possible for Fernanda to avoid notice for all these years,” Gaughran wrote to The Post. “Expeditions to the island can be difficult, so there are likely many places for tortoises — even giant ones! — to hide.”

Now that they’ve found Fernanda and confirmed that she is a member of the once-considered-extinct species, conservationists have to begin drawing the species away from the brink.

“The finding of one alive specimen gives hope and also opens up new questions, as many mysteries still remain,” said ecologist Adalgisa Caccone, a senior author of the study, to Princeton University. “Are there more tortoises on Fernandina that can be brought back into captivity to start a breeding program?”

It’s gone different ways in the past.

The study noted the success of 3,000 individual tortoises of the Espanola Island species being recovered from only a dozen surviving females and three males through a dedicated captive breeding program. One tortoise, Diego, is father to upward of 800 offspring. The breeding program was so successful that it was retired.

On the other hand, there was Lonesome George — who had an “apparent aversion to female tortoises,” National Geographic reported, and failed to breed before dying in 2012, becoming the last of the Pinta Island subspecies.

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For now, there are no known tortoises in her species for Fernanda to begin breeding with.

Even if Fernanda is the last fantastic giant tortoise, the study’s authors say that her genome sequencing is already helping them learn more about the evolution of giant tortoises.

And Fernanda is “becoming a conservation icon,” hopefully inspiring others to care more about biodiversity and the extinction crisis, Evelyn Jenson, a biologist and molecular ecologist who co-authored the study, told The Post.

But the researchers, and other conservationists, are not giving up yet.

Tapia wrote that year that he now has hope that tortoises exist in other parts of the island with similar environmental conditions.

If others exist, they’ve successfully evaded detection during wide searches of the island, the study wrote. But researchers noted that encouraging signs of other tortoises — from scat to tracks — have been found on Fernandina. Expeditions are planned for the near future to look for them.