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.

Bururi Long-Fingered Frog Rediscovered
Herpetologists from the California Academy of Sciences and University of Texas at El Paso discovered a single specimen of the Bururi long-fingered frog (Cardioglossa cyaneospila) during a research expedition to Burundi in December 2011. The frog was last seen by scientists in 1949 and was feared to be extinct after decades of turmoil in the tiny East African nation. California Academy of Sciences
Coelacanth
One of the best known examples of a Lazarus species is the Coelacanth, a spiny, prehistoric fish. The fish grows up to 6 feet (1.8 meters) long but is worthless as food since its flesh has a foul taste. Coelacanths were thought to have gone extinct 65 million to 145 million years ago at the end of the Cretaceous period until a fisherman caught one off the coast of South Africa in 1938. South African and Indonesian fishermen often catch specimens while fishing for oilfish, which feed at the same time as coelacanths. Reuters
Mahogany Glider
Found in Australia, naturalists first described the mahogany glider in 1883. The species was next seen in 1989. The mahogany glider is a marsupial, a relative of the possum and grows up to 10 inches (26.5 cm) long. The mahogany glider is endangered since crop and cattle farmers clearned most of its habitat. The Queensland Parks and Wildlife Service began a preservation program in 2000 to try and recover some of the population that was lost. Rainforest Rescue
Takahe
The takahe is a small, flightless bird native to New Zealand. Thought to be extinct in 1898, naturalists rediscovered the bird 50 years later in 1948 during a planned search. The bird became nearly extinct from over-hunting and loss of habitat along with the species's long life, slow reproduction and inbreeding. The small population makes it difficult to help the takahe recover, and the bird is currently classified as endangered. Credit: New Zealand Department of Conservation N.Z. Dept. of Conservation
Furbishs Lousewort
Lazarus species aren’t only animals – there are several plant species that have reappeared after being feared extinct, too. One example is furbish’s lousewort, an herb found on the shores of Maine and New Brunswick. Furbish’s lousewort was discovered in 1880, but was considered extinct a short time after. It wasn’t discovered again until 1976, when researchers were assessing the environmental impact of a potential dam. U.S. Fish and Wildlife Service
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