A newly discovered species of Ecuadorian frog has a secret weapon: A spine on the side of its thumb.

These tree-dwelling amphibians likely use their special digit to puncture the skin of predators or competitors within the same species, says study leader Santiago Ron, an evolutionary biologist at Catholic University of Ecuador.

Ron and colleagues found Hyloscirtus hillisi during a two-week expedition in Cordillera del Cóndor, a remote, little-studied region of the Andes that's also under threat due to mining. (Read about a bizarre horned frog rediscovered recently in Ecuador.)

"We walked two days along a steep terrain. Then, between sweat and exhaustion, we arrived to the tabletop, where we found a dwarf forest,” field biologist Alex Achig said in a statement. “The frogs were difficult to find, because they blended with their background.”

View Images The odd extra claw on both male and female H. hillisi is likely used as a defense mechanism, a new study says. Photograph by Gustavo Pazmiño, BIOWEB Ecuador

Odd though it is, the claw-like structure exists in four other species of related frog, notes Ron, whose study recently appeared in the journal ZooKeys. A few years ago, one of those species, Hyloscirtus condor, used its claw to tear through a latex glove and scratch the hand of the person collecting it, he added.

Plenty of other animals have funky fingers and tricky toes: Check out these animals that are having their very own digital revolution.

Polydactyl Cats

Cats normally have five front and four back toes—you can call it one for each life—but felines with polydactyly, Greek for “many digits,” can get six toes on front or back feet or both.

They’re not a breed—any domestic house cat can be a polydactyl cat if they have the gene.

This Tropical Frog Has Special Thumbs Just for Mating Male smoky jungle frogs possess a black spine on their thumbs used for holding their partner during mating.

The most famous of these kitties are probably the six-toed cats of Key West’s Hemingway House, descendants of a six-toed cat given as a gift to the famous writer.

Giant Pandas and Red Pandas

Giant pandas and red pandas are distant relatives, but they share an interesting trait: A false “thumb."

This superfluous digit is actually an extended wrist bone, hidden under the skin just south of the pinky, and helps them grasp the bamboo that’s a staple in both species’ diets.

Why hasn’t it evolved into a true thumb?

It could have, says Stephen Phelps, a geneticist at the University of Texas at Austin, but as far as harvesting bamboo, these species “seem to be doing great as it is,” he says.

Aye Aye

This endangered Madagascan primate has spidery hands with one very long middle finger. For insects, it’s the finger of death. (Related: “Weird Animal Hands: Demon Primate, Flappy-Armed Frog and More.”)

Aye ayes tap the trunks of decaying trees with their middle finger and listen for the sound of skittering insects inside.

If they hear one, the bug-eyed predators will deftly pluck out the insect with the same weirdly long digit.

Elephants

Elephant toe bones are oriented upright, so if you could see inside their feet, they’d seem to be walking on tip toe; picture pachyderms on point, like a ballerina.

You’d also see a smaller “predigit,” or sixth “toe,” a modified structure in all four feet that anchors the tendons, similar to that of the giant panda’s extra thumb, says John Hutchinson, an evolutionary biologist at the Royal Veterinary College in London. (Read about the African elephant’s complex sign language.)

The elephant forms its sixth "toe" from existing sesamoid bone, or as Hutchinson describes it, "old material." That's "rather than making a whole new digit, which is very rare in mammals,” he adds by email.

It's a handy adaptation: Hutchinson and colleagues have found that this hidden toe helps support the animal’s weight.

And that’s a faux-toe finish.