The Underground Tail-Hunter is only mentioned as a picture of an egg in The Complete Book of Dragons. Because the author's dragon names are typically quite literal, we might assume that the Underground Tail-Hunter is a type of Cave Dragon (underground), and that it hunts for tails (would that mean humans are off the menu?). They appear to have their own tails, so its also possible they hunt with their tails rather than for tails.
- The Complete Book of Dragons: A Guide To Dragon Species, Cressida Cowell. 2014