Ross G. R. Caldwell wrote:My sources which discuss the iconography of Fama don't identify the captives. This old article seems to discuss the state of the question up to 1937 however -
Shorr, D. C, "The Identification of the Captives in Petrarch's Triumph of Fame".
Die graphischen Künste, NF, Bd. II, S. 41 — 44.
Maybe you have access to this article.
Okay, found something - "Spendio" and "Machio". Sara Charney, "Artistic Representations of Petrarch's Triumphus Famae
", in Konrad Eisenbichler and Amilcare A. Jannucci, eds., Petrarch's Triumphs: Allegory and Spectacle
(University of Toronto Italian Studies 4; Doverhouse, 1990), pp. 223-233.
"A second iconographic difference between the [Domenico di] Michelino "cassone" and the Darmstadt codex concerns the presentation, on the "cassone," of two men walking beside the horses with their hands tied behind their backs. Malke observes that these two characters may be seen on an earlier "cassone" of the "Triumph of Glory." Their identification, in the early-mid Quattrocento, is unknown. In two late-fifteenth-century engravings of the fine manner style, two nude figures in similar poses are accompanied with the names Spendio and Mahio/Machio. They are not mentioned by Petrarch, and it has been conjectured that they represent the prodigal and the fool, or Spendius and Mathos, leaders in a rebellion against Carthage after the first Punic War.(27)
Note 27 - D'Essling and Müntz suggest that Spendio and Mahio/Machio are personifications of two vices, possibly of prodigality and of folly. See p. 130. Dorothy Shorr identifies the two men with the historical characters Spendius and Mathos. For a discussion of Shorr's views and facsimiles of the engravings see Arthur M. Hind, Early Italian Engraving
... 1: 35; 2: plates 21 and 24. Hind dates both engravings ca. 1460-1470. They are located in the Albertina, Vienna."
(pp. 228, 233)