Researchers in Africa recently rediscovered a single specimen of a long-fingered frog, a species thought to be extinct since 1949. The male frog has a long finger akin to the ring finger on humans.

Burundi, where the frog was found, is one of the most densely populated countries in Africa. But to researcher's surprise, they were able to find the frog quite easily.

I thought I heard the [frog's call] and walked toward it, then waited, David Blackburn, lead researcher and assistant curator of herpetology at the California Academy of Sciences, said in a statement. In a tremendous stroke of luck, I casually moved aside some grass and the frog was just sitting there on a log. I heard multiple calls over the next few nights, indicating a healthy population of the species, but I was only able to find this one specimen.

Species such as the long-fingered frog that disappear for years before resurfacing are known as Lazarus species, named after the biblical character Jesus raised from the dead.

Click through the slideshow for examples of some Lazarus species.