Deadly Nadders can raise the hundreds of sharp spines that cover their tails and fling them with incredible accuracy. But when the shooting starts, there is no safer place to be than face-to-face with a Nadder - If you stand right in front of its nose, a Nadder won't be able to see you. They often prune and groom themselves, and some say they can fall in love with themselves.
Nadders are some of the more common dragons and can be seen in most episodes/movies. The most known Nadder among the dragon riders is StormFly (Astrids Dragon).
He can find anything on scent, (ex. when he found Hiccup in Valka's nest based only on Hiccup's lost helmet). Rumblehorns look like a truffle pig mixed with a rhino, but much bigger. They have a chitinous green-red iridescent coloring and surfacing of a scarab beetle. They keeps their battle axe-shaped muzzle in the dirt, sniffing things out.
Rumblehorns are quite rare and can only be seen in HTTYMD 2 and Dragons: Race to the Edge. The only Rumblehorn that we currently know is Skullcrusher (riders include the late Stoic The Vast, and Eret son of Eret).