The lines are the crocodiles wide-open mouth... ... but yeah, I'm not a fan of this kind of mnemonic. It requires remembering a heap of details, such as which way the crocodile is facing, and does it prefer to attack the larger number or the smaller number - and how the relates to negatives... Which I think is surely more difficult than just remembering that the large end of the wedge is the larger number, and the small edge of the wedge is the smaller number.

That said, having multiple different ways of remembering something is often helpful, particularly when getting started. (I remember having a bunch of different ways to remember which was "left" and which was "right" when I was a child. But now I don't think about any of those things anymore.)