 In later versions of the story, the ram is said to have been the offspring of the sea god Poseidon and Themisto (less often, Nephele or Theophane).The classic telling is the "Argonautica" of Apollonius of Rhodes, composed in the mid-third century BC Alexandria, recasting early sources that have not survived.Another, much less-known Argonautica, using the same body of myth, was composed in Latin by Valerius Flaccus during the time of Vespasian.