Lundehunden are one of the most interesting dogs out there. Watch this video and note their genetic polydactyly and hypermobile joints, specialized for hunting puffins on cliffs where it would be dangerous for humans to tread. Absolutely amazing. They were almost eliminated, and have been rebuilding their stock and seeking admission to the AKC. Unfortunately, as in most cases where you try to rebuild a breed from a very small pool of individuals, they're struggling with a lot of genetic health issues, especially GI problems, making this a VERY high-maintenance dog currently. Some call for selective outbreeding, but in general they're trying to address the issue with massive screening and searching for any positive mutations.