Labeled one of the "world's weirdest" for the unlikely ways it rears its young and compared to an "overweight leaf" because of its appearance, Northern Darwin's Frogs haven't been seen in the wild since 1980 and are believed to be extinct, according to National Geographic (also the source of those nicknames). This time, it wasn't completely humanity's fault, but also the result of fungal infection.

Northern Darwin's Frogs were discovered by Charles Darwin in 1834 (and later named in his honor) during an expedition to the island of Lemuy on Chile's western coast. By the time scientists demarcated Northern Darwin's from Southern Darwin's in 1975, the Northern species was on its way to extinction, according to Nat Geo. The southern version is nearly extinct from the same fungal disease. The map below tracks the (previous) presence of Northern Darwin's in blue, Southern Darwin's in red and an area where the two co-existed in yellow.

Darwin's Frogs were given their name because of a unique adaptation found in males. Fathers incubate eggs in oversized vocal cords (why they resemble overweight leaves to some) and continue to hold their children like kangaroos even after they are born -- letting them out for the occasional breath of air until they are competent to live on their own, according to Nat Geo. With such a safe pathway into adulthood, one would think Darwin's Frogs immune to extinction.

But they weren't immune to chytrid disease, a fungal infection that's affected several species of amphibians around the world, according to research published Nov. 20 in the online journal Plos One. Extinction by disease is extremely rare, according to study lead author Andrew Cunningham.

"Only a few examples of the 'extinction by infection' phenomenon exist," Cunningham, a zoologist at the Zoological Society of London, said in a statement.

Cunningham and his team discovered the presence of chytrid disease in every area where Darwin Frogs had been present. To confirm the link, they caught several Southern Darwin's and compared them to preserved samples of Northern Darwin's from the 1970's. Nearly 13 percent of the most current samples were infected by chytrid compared to one percent of the old samples. The researchers added that deforestation was also to blame, according to Nat Geo.

"Amphibians have inhabited the earth for 365 million years, far longer than mammals. We may have already lost one species, the northern Darwin's frog, but we cannot risk losing the other one," said Soto Azat, who also contributed to the research. "There is still time to protect this incredible species."

Captured Souther Darwin's samples below: