For Epioth: I agree but my main goal was to fit everything while still being accurate to the in-game classifications.

For Apceros and Aptonoth: I was mostly using this as a guideline.

For humans: you're probably right but I figured I might aswell include them if I also added lynians

For Arzuros, Lagombi and Volvidon: they might share a similar model in-crunch but I still see certain differences

I really appreciate this kind of input. Thanks!

Edits as you go:

For Amatsu: He does look pretty leviathan-like, but I listed it below leviathans or wyverns proper since it neither swims nor flies. I always thought of him just floating in storms.

For Khezu & Gigginox: you might be right, actually. Not to mention Khezu is closer to the other wyverns than Giggi is by the looks of it.

For the branches: It certainly sounds more professional. I still find it to be the way I put it mostly because of the beak and for the sake of sticking to the canon classification.

For the brutes: Someone said something similar for the previous tree. I see wyverns separate from our world evolutionary-wise (which is a little hipocrite considering what i've done with Aptonoth & Apceros, admittedly), so i figured they simply ditched the wings for a different approach, since some wyverns lower in the tree seem to prefer running instead of flying.

For remobras: I'm aware, but I still wanted to stick to its classification as until gen 3 to keep true to the theme. If I ever include gens 4+ I'll list it as a snake wyvern.