No seriously. Any scientists/biologist here to help? Even evolutionary wise it seems to be a grey hole; it has no living close relatives and very few fossilised ones.
It is an honest to God enigma. A cool looking one, but still.
-blam!- it, it might as well have been a chimera.
Just stick a beaver, a duck, an otter and a snake in a blender and you got yourself a waddling/paddling mess.
-
Somebody else said they're aliens. I'm going with that