Some critter ideas I liked from Sierra's Quest For Glory series, when they went to the jungles:
Meerbats (Meerkats, with wings)
Demon Worm (use the Death Worm from ToH)
WereJaguars
Giant Ants
Some other ideas:
Stirges seem to fit in nicely
Caterwauls
Wemics (more of a Plains creature, actually)
Flying MonkeysTabaxi (the villains of my own IncaMaya game)
Those winged snakes which generated sparks, wossnames
Tree Trolls (Small trolls from an issue of Dragon magazine)
Any number of nasty, poisonous bugs
I made an intelligent Tree Slime awhile back.
- Devon