Seadramon is a fish, not a reptile. I don't know if that's actually an unpopular opinion, but I felt it needed to be said.
Dragons aren't fish, though. It's a dragon that lives in the sea. Like how Lugia lives in the sea in Pokemon but is not only not a fish it's not water type.
I think what they're alluding to is the lore of Magikarp to Gyrados. A carp that becomes a dragon.
I don't recall Seadramon having that mythology associated with his design.
Basilosaurus, in spite of looking more like a reptilian cetacean could work as a source of design inspiration for Seadramon.
well Betamon isnt a Dragon, so it's basically the same thing.
Supposedly, not that it's official, it's based off of Dimetrodon.
Uh…no?
Betamon is an amphibian, and Dimetrodon was a synapsid. The two aren’t even remotely similar except for having fins on their back…which lots of different creatures have had throughout the history of life on Earth. Whoever told you that was clearly making shit up.
(Besides, even if Betamon was a Dimetrodon - which he isn’t - Dimetrodon wasn’t a dragon or even a reptile. It was a synapsid and is more closely related to mammals like dogs or cats that it was to any reptile, including the dinosaurs)
You do realize I said it wasn't official, right?
Betamon is an Amphibian Digimon. It walks on four legs. Its personality is gentle, but although it is a docile Digimon, once Betamon is angered, it emits its "Electric Shock" (Dengeki Biririn) from its body. Attacks Electric Shock (電撃ビリリン, Dengeki Biririn?): Generates more than 1 MV of electric...
digimon.fandom.com
Just hope that was clear.
Nevertheless, my response was to Muur's response to me concerning Tortoiseshel's allusion to Seadramon's origins being akin to this:
Not that I want to get into it over Betamon, to each their own, but considering that Dimetrodon was semi-aquatic (or at least it is speculated to have been), I think it's safe to assume that they could have been playing loosely with the term amphibian. Given it a more pudgy frog like appearance (Probably a Pacman frog.), and drawing from other semi-aquatic animal sources.
This would work as well:
en.m.wikipedia.org
This is off topic, but I've long speculated, at least in so far as some OG digimon lines, that many were meant to be reptilian/dinosaur like as they progressed. Palmon has always made me lean in that direction. Would have liked for her to become Petaldramon > Toropiamon/Entmon > Ceresmon in A2020 as a slide form.
Unpopular opinion:
In retrospect, as much as I enjoy new digimon and lines being introduced, I personally think it goes against what Digimon was meant to be. Perhaps it was better with limited higher forms.