>>24644065English costumization. Venusaur (the whole Bulbasaur line) actually don't have anything to do with dinosaurs, or toads for that matter. They're supposed to be bizarre, as in, a mix of various creatures. Kinda like if you imagine you'd pull on of those plants and find out there was a living animal underneath that connected to the plant.
The bulba line look standard reptilian and also amphibian, but they also have ears and canines which only mammals have.
The french name for this Pokemon best captures it. Herbizarre. The japanese name is a pun as in "Vine", "Herb", etc with a pun with "What's is it?". Because we don't know what it is.