User blog comment:Kogath/Monster Hunter: World Discussion/@comment-25083735-20191105005322/@comment-31029678-20191110113422

"We've taken to using the term Elder Dragon for any creature that defies ordinary classification, but I suppose you could call them a type of phenomenon: disasters, cataclysms, living, breathing forces of nature." the most recent definition we got.

Dalamadur isn't in the Snake Wyvern class despite being introduced alongside Najarala, like you said Amatsu isn't a Elder despite being introduce in a game where other Leviathans were present... either devs are totally unaware of how classification in real world works and I really doubt (still there are some serious odd cases even in the real life classification) or there's clearly more going on with Elders

Probably even after the introduction of more snakes, horses and mollusk... Kirin, Yama or Dalamadur would still remain classified as Elders.

I agree that from a real-world point of view the MH classification doesn't make sense, but I'm saying that it doesn't have to follow logic or real life biology (Black Dragons already break those rules, afterall they were made without litterally thinking about logic explanations)... it just have to follow its own rules and its own logic.