>>44561475>>kingdra is a dragon because of how it evolves>she doesn't knowBehold, Phyllopteryx taeniolatus, also known as the Weedy or Common Seadragon. The common name of these fish, which are closely related to seahorses, is probably the reason why Kingdra is a Dragon-type and, indeed, why Seadra and Horsea were categorized as the Dragon Pokemon in the Pokedex all the way back in Gen I.
Another related species, Phycodurus eques or the Leafy Seadragon, was pretty blatantly used as the primary reference for Dragalge's design.