Potential Secret World for Series
I love the idea of a hidden secret world for the liminal species and the normal versions.
Personal Version of the verse
In my own personal verse of this world I'd make dragons true reptiles. There are other things I'd add too.
Thoughts on Naming the Liminal Species
I think they should take greater care to name these so as to make a distinction between a liminal species and a non liminal one that shares the same name, like the Bat, White Tiger, Queen Bee, Honey Bee, Salamander and others.
Opinions
It seems to me that the rules on intersecies breeding about no sex is kinda silly. And unenforceable.
Species Creation
I created a species called a Dragomorph. Dragomorphs resemble Dragonewts except they are stronger and have larger wings. They are much more draconic than their cousins. They possess immense strength and durability. And they posses the ability to disguise themselves as humans, or turn into other animals and monsters. They can also turn into dragons. They are mesothermic which means that they can regulate their body temperature to a certain extent. They lack the Dragonewts scale weakness, and they can breathe fire. They generally forgo wearing clothes.