Yeah, it's sort of a running theme that all the "natural" animals of Avatar were crossbreeds of two or more earth-animals, from cute little duckturtles to dragonfly-winged snakes to large rolly armadillo-tigers. They even poked fun at it at one point, let me wiki up the exact quote:
Katara: The King is throwing a party at the palace tonight for his pet bear.
Aang: Don't you mean platypus bear?
Katara: No, it just says, 'bear'.
Sokka: Certainly you mean his pet skunk bear?
Toph: Or his armadillo bear?
Aang: Gopher bear?
Katara: Just, 'bear'.
(short pause)
Toph: This place is weird.
Which is why "pigmaggots and frogeels" made me think of it.
Of course, you could do worse than that for AW: stick to scavengers, vermin, and poisonous/dangerous things, and you've got a strange and twisted mutant ecology just waiting to inflict hardship upon your PCs!