Draconic ancestral development for the Aerie.
Draco Arboravus; from this tree dwelling ancestor came contemporary westerns, those that lost their forelimbs became wyverns, and those who returned to the ground and seas developed into various wyrms and eastern dragons.
Those that came before the protodragon dwelt primarily in the water, hence the remnant of a paddle-like crocodilian tail. An evolutionary development tree will be coming soon.
Next is Hexapteryx Archeophis. (Names aren't very consistent at this time, pay no heed) This guy is a little further along the line in terms of flight development. His middle limb set is being relegated to primary wing duty, and his forearms are taking on climbing. The tail is looking a little prehensile as well, and his body is overall more mammalian in structure. His larger teeth suggest he's tackling fleshier prey.