- Scientists estimate that they have not yet identified 86% of species on Earth, and 91% of ocean species.
- In the last decade, however, they've made some exiting discoveries, including cave-dwelling translucent snails, ancient human ancestors, and a new species of orangutan.
- Here are 14 fascinating animals unearthed in the last decade.
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Earth is crawling with lifeforms, and most of them are unknown to us humans.
A 2011 study estimated that scientists had not yet identified 86% of species on Earth, and 91% of ocean species. Scientists chip away at that number every year, traveling to remote mountain forests and the deepest regions of the seas to catalogue new animals.
They've uncovered bizarre creatures in extreme environments and unknown mammals hiding in plain sight.
Here are 14 fascinating animals that scientists found in the last decade.
Earth is home to an estimated 8.7 million species, though the vast majority remain undiscovered. In the last decade, scientists have found some surprising creatures.
In 2017, researchers announced that the newfound Tapanuli orangutan is the seventh known great ape species — and the world's rarest.
There are only about 800 Tapanuli orangutans left, and they're threatened by hunting and habitat loss.
"Great apes are among the best-studied species in the world," conservation scientist Erik Meijaard said in a press release. "If after 200 years of serious biological research, we can still find new species in this group, what does it tell us about all the other stuff that we are overlooking?"
The olinguito is the first carnivore discovered in the Western Hemisphere since the 1970s.
In 2013, a researcher uncovered decades-old specimens of the small carnivore at the Chicago Field Museum. They had been labeled as olingos, a similar species, but olinguitos live at a much higher elevation than olingos.
So a team trekked out into the clouds forests of Ecuador to find this animal — the smallest known member of the raccoon family.
"The age of discovery is not over,"Kristofer Helgen, curator of mammals at the Smithsonian's National Museum of Natural History, told National Geographic at the time. "In 2013 we have found this spectacular, beautiful animal, and there's a lot more to come."
In 2017, a giant rat fell from a tree, straight into the hands of a mammologist who knew he'd found something new.
Solomon Islands locals had long spoke of the coconut-eating, 2-pound Vangunu giant rat, but no scientist had ever confirmed its existence. Then a park ranger caught one scurrying out of a tree that loggers had cut down.
"It's the first rat discovered in 80 years from Solomons, and it's not like people haven't been trying — it was just so hard to find," Tyrone Lavery, the mammologist who first confirmed the species with DNA analysis, said in a press release.
Scientists consider the giant rat to be critically endangered because of logging. The rat that Lavery found in the felled tree died soon after.
"It's getting to the stage for this rat that, if we hadn't discovered it now, it might never have gotten discovered," he said. "The area where it was found is one of the only places left with forest that hasn't been logged."
Another adorable tree-dweller, the dwarf lemur, is smaller than a squirrel.
The fat-tailed dwarf lemur is the only known primate that hibernates for an extended period of time. To prepare for their seven-month sleep, the animals gorge themselves on fruits and flowers to store fat in their tails — up to 40% of their body weight.
Other newly discovered tree creatures aren't as cute and cuddly. This Phuket Horned Tree Agamid was found in Phuket, Thailand.
The spiky lizard is threatened by habitat loss and attempts to collect it to keep as a pet.
A tiny frog smaller than a dime, discovered in 2012 in the rainforests of New Guinea, is the world's tiniest vertebrate.
At an average of just 7.7 millimeters long, the little frog inhabits southern Papua New Guinea and eats tiny invertebrates like mites.
"I think it's amazing that they're continuing to find smaller and smaller frogs," Robin Moore, an amphibian expert who wasn't involved in the finding, told National Geographic. "They're adapting to fill a niche that nothing else is filling."
Through DNA testing, scientists discovered a new species of pink river dolphin in the Amazon's Araguaia river basin.
The Araguaian river dolphin is the first new river dolphin species discovered in a century, according to National Geographic.
The fire-tailed titi monkey and a honeycomb-patterned stingray were among a same batch of 381 new species discovered in the Amazon rainforest.
"We're in 2017, verifying the existence of new species, and even though resources are scarce, we are seeing an immense variety and richness of biodiversity," Ricardo Mello, who coordinates the World Wildlife Fund's Brazilian Amazon program, said in a press release about the finding. "This is a signal that we still have much to learn about the Amazon."
On the other side of the world, in the forests of Vietnam, cameras spotted this long-lost mouse deer in November.
Though it's not technically a newly discovered species, conservationists had feared that the silver-backed Chevrotain was extinct.
Researchers who discovered this African fish with gleaming purple scales named it after Wakanda, the fictional home of Marvel's Black Panther.
Its deep-purple scales, set in a chain-link pattern, reminded scientists of the high-tech suit worn by the superhero Black Panther.
So they named the newly discovered, 2-inch-long fish "Cirrhilabrus wakanda." Even its common name, "vibranium fairy wrasse," gives a nod to the fantastical, near-indestructible metal that lines the Black Panther's superhero suit.
The deepest reaches of the ocean harbor all kinds of strange, unknown creatures. The last decade of deep-sea exploration has revealed several of them.
This animal resembles a bottom-dwelling jellyfish, but the team of deep-sea explorers that discovered it isn't sure what kind of creature it is. The deep-water denizen may belong to a new species, but that has yet to be confirmed.
The team that spotted it has discovered three or four new species on every deep dive they've done, but leader Victor Vescovo noted that this particular animal was "very, very unique looking" compared to the others.
In one of the world's deepest cave systems, scientists spotted a new, translucent snail.
The new species, called Zospeum tholussum, lives 980 meters (3,200 feet) below ground in the Lukina Jama-Trojama cave system in Croatia. There's no light that far below the Earth's surface, so the tiny snail has no need for sight.