Unknown Creatures

Unknown Creatures are species that only had brief cameos in the Anime and Manga without any detailed information of them.

Description
The displayed creatures often appear to be reptilians, birds, sea creatures, as well as airborne creatures.

Trivia

 * In a tweet replying to an english fan, Akihito Tsukushi revealed names of unknown creatures.
 * In Riko's day and age, the creatures that look like large tentacles Ganja encountered when meeting the Interference Units in the 6th layer haven't been identified yet. Riko's timeline has a similar creature in the upper layers called a "Honmurodouko", but is only about as big as a rope, so it's probably a different species altogether.