The Pokedex entries make more sense when you realize they were probably written by ten year old kids. And writers have no real sense of scale (see most science fiction ever), so paying attention to how tall or how heavy Pokemon are will only cause headaches, especially when some Pokemon really don't match their height in our minds (the anime's really good at giving Pokemon their own height that seems much better, such as Arcanine).
And Cubone was made before breeding was a thing, so blame retcon. And Kangaskhan. And Onix too, I suppose.