Slitherfangs are mentioned briefly in several books. Specifically, the species of Burrowing Slitherfang is mentioned, however this specific species seems different than a few mentions of the unspecific "Slitherfang". Burrowing Slitherfangs are large, tentacled, underground-dwelling creatures similar to Monstrous Strangulators. The simply-mentioned Slitherfang seems to be a relatively small (perhaps the size of a large dog), surface-dwelling dragon sometimes used as a Hunting Dragon by Vikings, and no mention of tentacles are made. The author most likely intended the Burrowing Slitherfang and the Slitherfang to be separate species.
Hiccup creates a ruckus aboard a Roman ship attempting to escape with Fishlegs and set free the dragons the Romans had captured. At one point, Hiccup used a dragon to aid Fishlegs in escape:
- "So Hiccup grabbed a passing Slitherfang and shoved it up the centurion's tunic. The centurion let out a bellow and dropped Fishlegs
A Slitherfang in the knickers is no laughing matter."
- ―How to Speak Dragonese
The Slitherfang seen here is small, able to fit under a human's garments.
In The Day of the Dreader, a How to Train Your Dragon novella, there is mention of Slitherfangs as hunting dragons:
Based on what we know about the Burrowing Slitherfang, one would not be clinging to the rafters in a Viking home, aiding humans.
In How to Seize a Dragon's Jewel, Slitherfangs are mentioned as being hazardous underground creatures and possibly being related to the Monster of the Amber-Slavelands, but this most likely is referring to the Burrowing Slitherfang.
- How to Speak Dragonese (Book 3), Cressida Cowell. 2005
- The Day of the Dreader, Cressida Cowell. 2012
- How to Seize a Dragon's Jewel (Book 10), Cressida Cowell. 2012