I don't think so. Life on Earth is so diverse already. Your best examples are animals that are close relatives already (birds and bats aren't all that far apart

I don't think so. Life on Earth is so diverse already. Your best examples are animals that are close relatives already (birds and bats aren't all that far apart in evolutionary terms, and their common reptilian ancestors already had by and large the same skeletal structure). Also, aerodynamics seem dictate most of the body shape. Butterflies on the other hand solve the problem of flight in a very different way. The movement of worms and snakes doesn't look very similar at all, and the same is true for fish and jellyfish. Really, the Na'vi are more similar to humans than humans look to most other species on Earth. You can't make a convergent evolution argument here unless you believe that intelligence somehow requires upright walking and a human-like face, down to the specifics of what facial expressions mean. I consider this highly implausible, even if it makes for a good movie.