i would say:
-Ivalice from FFXII
-Grand Pulse from FFXIII
And what makes them interesting?
Ivalice have interesting ecosystems like the Yensa Sandsea, an strange desert with sand which flows like water, the climate is tropical and its sands are inhabited by the Yensa, an strange strain of fish which can swim in the sand, the fish produces a mucus that allows to retain moisture, also its hard scales allow them to swim without getting hurt.
other species of the world of FFXII have interesting adaptations, for example the Urstrix, a giant terrestrial Owl with an erected stance which uses its wings for hunting prey (they kill their victims with punches and pecking).
Ivalice also is the home of several species of floating fishes, i dont get how they get to breathe out of the water
there's also the Sleipnirs, a group of horses which have developed armors in their backs, or the Garuda, giant birds which fly using skin instead of feathers, they also lack a beak and instead they have a mouth full with teeth. or the Slaven, a reptilian bipedal creature which was used as cargo moving.
--------------------------------------------------------------------------------------------------------------------------------
about Grand Pulse, since i have never played FFXIII, i at least have seen some of the species. the Sahajin for example, a classic creature of the FF universe, is an amphibian or fish-like creature with humanoid traits.
there's also the Adamantoises, huge Tortoise reptiles with adaptations similar to those of sauropods,
