Which primordial sea god was the father of the Harpies?

Thaumas was the primordial sea god who fathered the Harpies with the Oceanid Electra.

According to Hesiod, Thaumas was a son of Pontus, the primordial sea, and Gaia, the earth. His brothers and sisters included Nereus, Phorcys, Ceto, and Eurybia, placing him within the ancient generation of sea deities that preceded the Olympian gods.

Thaumas married Electra, one of the daughters of Oceanus and Tethys. Their children included Iris, the rainbow messenger of the gods, Arke, a former messenger of the Titans, and the Harpies. In Hesiod’s account, the Harpies were Aello and Ocypete, though later writers added or substituted Celaeno and other names.

The Harpies were winged female beings whose name is connected with snatching or carrying away. Their family tree varies across ancient authors, so some later traditions give them different parents. That variation does not displace Thaumas as the standard answer in the Hesiodic genealogy.