What role does the phallodeum play in caecilian reproduction?

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Zoom in on the serpentine locomotion of the limbless, amphibious caecilian over soil — Gymnophiona Caecilian moving over soil.

In caecilians, the phallodeum serves as a specialized copulatory organ in males that facilitates internal fertilization. It is a modification of the cloacal wall that allows the male to transfer sperm directly into the female's reproductive tract.1

While some amphibians rely on external fertilization or the deposition of spermatophores, all caecilians are believed to utilize internal fertilization, making the phallodeum a critical adaptation for their reproductive success.21