The Lundehund is a polydactyl dog which means that instead of having four toes per foot, the Lundehund has six – all fully formed, jointed and muscled. Polydactyl dogs aren’t exceedingly rare, it’s just that in most other breeds, those extra toes are dew-claws and mostly non-functioning. As you can see from one of the images, Lundehunds need these extra toes to gain purchase and additional footing on steep (sometimes slippery) rocks where its prey – the Puffin bird – lived.

Images from Pinterest and happily credited upon receipt of information.