Madokajack

Madokajacks (マドカジャク) are large reptilian creatures that live in the 3rd layer.

Description
The arms and legs of Madokajacks have evolved to have membranes that let them glide on the wind currents in the Great Fault and they feed on creatures that live along the walls. Their eyes are on stalks that stick out from the sides of their heads, and their jaws come together in huge pincers, giving them an insect-like appearance.

Madokajacks create holes in the walls of the 3rd layer and live in colonies.

They don't seem to be very sanitary creatures. When Riko and Reg accidentally stumbled upon one of their nests, it was filled with feces, eggshells, and remnants of past meals.

Trivia

 * In the Anime, while traversing the 3rd layer, Reg and Riko stumbled upon an ancient ship buried in the side of the cliff. Upon investigation, it turned out to be a Madokajack's lair. In the Manga however, the lair belonged to the same Crimson Splitjaw that attacked Riko before she found Reg.
 * Its name is possibly a combination of the word for circle (Madoka) and the name of a family of weaverbirds (Jaku/Suzume).
 * Their danger classification is unknown, but they seem highly agressive; as seen with Riko and Reg.