Theory: Mawile is secretly an evolution of Helioptile
So I just watched the newest dex episode on mawile, and I noticed that Alex and Kellz were stumped on why mawile's jaws were, in the pokédex, said to be mutated horns. So I thought I would share my personal theory. Note that this is copied from smashboards, where I originally posted this theory, so it will be starting from the very beginning.
So, I stumbled upon a piece of artwork titled "Mawile Evolution" on deviantart that showed mega mawile, mawile, and. . . helioptile? The helioptile really looked like it actually belonged in mawile's evolutionary chain. The artist said that he just added helioptile in there for the heck of it, and there are plenty of things online where people have said helioptile should evolve into mawile as well as heliolisk, but none of them offered an explanation, just some visual evidence. Well, I have done some research, and I can conclude that it is extremely possible that mawile is a long lost evolution/mutation of helioptile.
So there are some initial clues right off the bat: mawile and helioptile both end in -ile, signifying that they are both reptiles, and mawile is slightly taller and heavier than helioptile, which is normal for evolution. Also, their color schemes are strikingly similar, as many people have already pointed out. But the next part is my own theory, and I argue that it makes a surprising amount of sense.
Helioptile gets all the energy it needs from the sun, by absorbing solar energy through the flap-like things on its head, thereby giving it electric power. Well, what happens if a helioptile is stuck in a cave (which is mawile's natural habitat I might add) Where there is no sunlight? Well, I theorize that it and its sun-powered appendages on its head get desperate for energy, so in order to prevent starvation, it evolves, into mawile! Even on mawile's pokedex entry, it says that its maw is actually horns, that have been transformed! But from what? Mawile has no confirmed pre-evolution! Well, a starving helioptile's horns turn from solar-power to meat-power out of desperation to survive. In this way, it also loses its electric typing since it loses solar power, and grows steel teeth, making it a steel type. Well, one might wonder why mawile appears to have some fur, when helioptile doesn't. This is just another one of helioptile's adaptations during evolution, since before it got stuck in the cave, it was accustomed to the constant exposure of sunlight, so being stuck in a cold, damp cave is very uncomfortable for the lizard, and it grows fur to cope with the temperature. So after all this, one question remains: helioptile has a tail, so why doesn't mawile have one? Well, real lizards can shed their tails in desperate times, but they loose many of the nutrients stored in them. Well, what if helioptile used its tail to store extra electricity, and when evolving, it sheds its tail out of necessity, since it no longer serves helioptile any purpose other than being a liability since other creatures could grab it by its tail? Once helioptile has gone through these transformations and adjustments, it is now much better suited to survive in its habitat, and becomes a mawile.
As with any theory, this idea is malleable, and can be changed if a problem or contradiction is found, so if there is any contradictory evidence out there, please let me know so that I may adapt this theory to fit around it, and if you have any more evidence to support this theory, please let me know as well, so that I may add it into the theory. I would also be glad to answer any questions or confusions you may have.