Scientists say a new species of giant tortoise has been discovered in the Galapagos Islands off Ecuador thanks to genetic testing.

The national park said in a statement Tuesday that the new tortoise was the 15th known species discovered on the archipelago. Four of those are extinct.

Yale University biologist Gisella Caccione led the investigation that identified the new species on Santa Catalina island. She said the discovery will help protect and restore the tortoise, whose numbers are estimated at 250. That compares to more than 2,000 of the other species living on the island, Chelonidis porteri.

The new species was christened Chelonoidis donfaustoi after park ranger Fausto Llerena.

The unique flora and fauna of the Galapagos inspired naturalist Charles Darwin.