Speothos venaticus is the least understood dog on the planet. I had no idea it existed before seeing it in The Life of Mammals. Known as the Bush Dog, or locally (Amazonia) as the Vinegar Dog, this is the only Canid with webbed feet. Why would a dog have webbed feet?
These dog are semi-aquatic(!) and hunt rodents and other small animals, occasionally diving to catch them. Bush dogs tend to be found in packs of 10-12, but occasionally appear solitary. They have a unique dentition (not surprising for such a derived species) that seems to emphasize ripping and tearing ability. You can view an excellent scan of a Bush Dog skull at one of my new favorite websites. Bush dogs were discovered as fossils in caves before live specimens were known to science. Speothos are still considered extremely rare across their range, which is not well defined.
David Attenborough once again provides the world with an excellent view of a rare animal.