Elizabeth Rivers is the name given by Philip José Farmer to the pregnant wife of Robert Gordon, who gave birth to Jongor after their aeroplane crash-landed in a dinosaur-ridden part of Australia (Jongor originally appeared in stories by Robert Moore Williams)
Her parents were Patrick Rivers and Nyad Drummond, through the latter of whom (as granddaughter of Sir Hugh Drummond, Bt. and Georgia Dewhurst) passed on to Elizabeth the genetic inheritence of the Wold Newton Family.
Details of the family are given by Farmer in "Jongor in the Wold Newton Family", removed from the draft of Doc Savage: His Apocalyptic Life and ultimately published in Farmerphile #12.