"Glider" is a term used in the series to describe Microraptor.
The only one ever seen in the series is Guido, who has also never seen another one like himself. It is unknown if Glider is the term used all over the world to describe Microraptor, or if other small, gliding creatures fall under this term, as Guido is the only one seen and he may have made up the term simply to describe himself.
