My seadragons begin as flopping mudskippers [https://en.wikipedia.org/wiki/Mudskipper]. They already have the front legs to pull them around. As time passes, they adapt to their environment and begin evolving into their secondary, humanoid form.
From something strange and a bit ugly looking, they metamorphose into the perfect predator. Humans are drawn to their dangerous sex appeal and the pheromones they produce. A seadragon rarely goes hungry once it attains a human-shape to wear.
