I have a clue, but that's it...
1) body shape - females should be larger and fatter if well-fed.
2) cloacal morphology - like Typhlonectes it appears that some other non-typhlonectid caecilians do have dimorphism with regard to cloacal morphology, but it might be far more subtle. If you have a good group of them, take photos of them from underneath in a bare aquarium and see if you notice some differences. This works for Geotrypetes - females have a smaller cloacal "disc".
If you don't have a good group and a high probability to have both sexes, well...who knows?
