In Greek mythology, Mopsus son of Ampycus (Ampyx) was an Argonaut seer, trained in augury and associated with Oechalia or Titaresia. He sailed with Jason, kept storm-watch with Acastus, and died of a serpent's bite in Libya. Distinct from Mopsus of Colophon (son of Manto), the seer who outprophesied Calchas — atlas id mopsus-colophon.
Adapted from Wikipedia, "Mopsus" · CC BY-SA 4.0
I.Argonaut seer
Apollonius names Mopsus son of Ampycus among the Argonauts: he reads bird-signs, shares night-watch with Acastus when a storm pins the ship, and later dies in Libya after a serpent bites him — a fate separate from Idmon's boar-death among the Mariandyni. Hyginus and Ovid likewise know an Argonaut Mopsus; Hyginus places him from Oechalia (or as a Titaresian).
This figure is a Lapith-linked augur of the voyage, not the Anatolian founder-seer of the Returns.
II.Homonyms
Wikipedia's main Mopsus article centers on the Colophonian seer (son of Manto by Apollo or Rhacius), rival of Calchas, and on Iron Age Cilician/Pamphylian "house of Mopsus" inscriptions. The atlas keeps that person as mopsus-colophon. A Thracian commander Mopsus and Virgil's pastoral singers of the same name are likewise separate. Id mopsus is only the Argonaut son of Ampycus.