I distinctly recall AD&D paladins being able to have mounts like griffons, dragons, and planar variants, but I cannot locate these rules. I'm aware Cavalier Paladins had some of these, though I'm not sure how that interfaced with their Holy Mount rules if at all. It seems we ran a Planescape campaign and someone had an elemental variant, following some "your mount is the equivalent of the nearest" or whatever. Perhaps exotic mounts were a dragon magazine or Skills & Powers/Player’s Option addition?
In sum: looking for the list of non-warhorse mounts.