This article lists the vast array of fictional animals found in The Edge Chronicles, a series of young adult books set in a fantasy world created by Paul Stewart and Chris Riddell.
For more information about the fictional world of the Edge, please see the similar article, Plants of The Edge Chronicles.
Evolution on the Edge happens at a much faster pace than on Earth. The half-formed mutants of Clash of the Sky Galleons have adapted very quickly to their sky-wreck environment. Of course, they are just overgrown sky-vermin. Sky-vermin are (from the looks of the Clash of the Sky Galleons) very adaptive creatures.
The high evolution rate could be explained by the existence of "Glisters", small seed-like objects that blow in from the open sky. When they encounter Riverrise, the source of the Edgewater, they somehow mutate into animals and plants of many forms.
Alternatively, these animals may already have existed, but were practically unknown and simply moved into a vacant niche.