More Wolverine frogs! Japanese species uses bony thumb-spikes to fight and hold onto mates | Not Exactly Rocket Science Discover Magazine, 19 Oct 2012
Zoologger: 'Wolverine frog' fights with retractable spikes New Scientist, 18 Oct 2012 The Otton frog has one more finger than other frogs – a finger with an extendable spike it uses to stab rivals
