Deep in the rain forest of Ecuador lives a very indecisive frog.

On a nighttime walk in 2009, scientist Katherine Krynak spotted a well-camouflaged, marble-size amphibian that was covered in spines. But when she brought it inside, suspecting it was a new species, Krynak found a rather smooth and slimy critter.

"I was so mad at myself! I thought I had brought back the wrong frog," said Krynak, who was surveying amphibian species in the Reserva Las Gralarias.

She hadn't. When she tucked a small piece of moss in the frog's container to make it more comfortable before releasing it back into the forest, the spines slowly reappeared.

"It was shocking. Vertebrates don't do that," she said. Inspired by its spiky physique, she dubbed it the "punk rocker" frog. (Also see "New 'Bat Frog' Found in Amazon, Named for Ozzy Osbourne.")

But it took Krynak and colleagues nearly nine years to gather enough data to prove it was a new species—and the first vertebrate known to change its skin texture.

Now the frog finally has a formal name: the mutable rainfrog, or Pristimantis mutabilis, according to a study published March 24 in the Zoological Journal of the Linnean Society.

Now You Spike It, Now You Don't

Krynak, a Ph.D. student studying amphibians at Case Western Reserve University, in Cleveland, didn't find another punk rocker frog until 2009, three years after the first sighting.

The second animal was covered in thorny spines, like the first, but they had disappeared when she took a closer look. It was only after seeing the spines reappear that Krynak realized the uniqueness of her discovery. (See "'Fantastic' New Flying Frog Found—Has Flappy Forearms.")

The team then took photos of the shape-shifting frog every ten seconds for several minutes, watching the spines form and then slowly disappear. It's unclear how the frog forms these spines so quickly, or what they're actually made of.

The scientists suspect the shifting skin texture functions as a form of camouflage—for instance, spikier skin might help the animal blend into mossy environments.

During their research, Krynak and colleagues also discovered that a closely related species, the Sobetes robber frog (Pristimantis sobetes), can also shape-shift.

All they need now is a bass guitarist for their punk rock band.