Atypical toes

Look closely at the 5th digit on the left in the photo above and you will see an unusual adaptation: a fearsome bony spine that extends through the skin of the "pseudothumb" when the male Babina subaspera wants to use it to hold a mate or fight a rival. The feature is all the more remarkable because it belongs to a frog, known as the otten frog or wolverine frog. These Japanese frogs have re-evolved the 5th toes on their front feet that other frogs have lost and have armed them with the retractable claws that leave the female frogs, their male enemies, and the scientists who study them scarred and bleeding. The otten frog joins a select group of animals that self-arm, including a newt (Pleurodeles waltl) that forces its ribs through its skin to produce protective barbs on demand and a hairy frog (Trichobatrachus robustus) that actively breaks its own bones to produce claws that puncture their way out of the frog's toe pads. You can see the rest of the "weirdly primitive-looking" otten frog here, but photos and wet specimens may eventually be all we have left. B. supaspera is endangered due to an invasive species, in this case the mongoose.

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Ribbit:

Princely frog

Microhylids

Frogs, deformed and fanciful

Elusive animals

Toads encased in stone