I've been working bit by bit on my Mutant Future house rules for char-gen in GamMarvel World. At first, for mutant plants and animals I figured I'd use what's in GW4. But I had second thoughts.
GW4 has about fifty animal types which can be used as is or as models for other types. Well, the ability score cap is lower in MF (a good thing IMO) so I adjusted all the scores. I was already not so fond of the fact that there are so many feline types in perticular on that list. So I started making up a more general one.
My new list has forty or so animal types, mostly pretty broad, with some sample specific species. So instead of having fox and wolf separate, there's one entry for Canine.
I still need to add specific animal abilities (senses, movement, etc). When I do that, some types will get a choice of special. So if you choose Snake, you might choose a poison bite or constriction attack. If you choose Marsupial you get a pouch, and can choose from jumping, climbing or prehensile tail (kangaroo, koala, possum). Something like that.
It may be more work than strictly necessary, but it is helping me consider just exactly what it means to be a mutant animal in the post-apoc future of the Marvel Universe. Some may be uplifted animals (Rocket Raccoon types) while others may have originally been descended from humans with animal-like mutations (The Beast, Wolvesbane, Squirrel Girl, etc.).
Mutant plants will be closer to the GW4 rules. "I am Groot!"