Theodontius was the author of a now lost Latin work on mythology. He was extensively quoted in Giovanni Boccaccio

Giovanni Boccaccio

Giovanni Boccaccio was an Italian author and poet, a friend, student, and correspondent of Petrarch, an important Renaissance humanist and the author of a number of notable works including the Decameron, On Famous Women, and his poetry in the Italian vernacular...

's Genealogia Deorum Gentilium

Genealogia Deorum Gentilium

Genealogia deorum gentilium, known in English as On the Genealogy of the Gods of the Gentiles, is a mythography or encyclopedic compilation of the tangled family relationships of the classical pantheons of Ancient Greece and Rome, written in Latin prose from 1360 onwards by the Italian author and...

, but is otherwise almost unknown. Boccaccio says that he knew Theodontius's work through the Collections of Paul of Perugia

Paul of Perugia

Paulus Perusinus or Pusinus was an Italian mytographer of the 14th century. He is extensively quoted in Giovanni Boccaccio's Genealogia Deorum Gentilium , but otherwise almost unknown...

, which Paul's wife burnt after his death (Genealogiae XV 6). In telling the legend of Bathyllus

Bathyllus

Bathyllus was a dancer/performer of pantomimus in Rome during the period of Augustus. Born in Alexandria, he was the favourite comedic performer of Maecenas....

, however, Boccaccio complains that Theodontius was illegible except for Bathyllus's birth, from Phorcys

Phorcys

In Greek mythology, Phorcys , a primordial sea god, generally cited as the son of Pontus and Gaia. According to the Orphic hymns, Phorcys, Cronus and Rhea were the eldest offspring of Oceanus and Tethys. Classical scholar Karl Kerenyi conflated Phorcys with the similar sea gods Nereus and Proteus...

 and a marine monster (Genealogiae X 7), so he may have seen some of Theodontius's own writings; sources disagree on this. Some authorities think Boccaccio invented him.

Outside Boccaccio, there was a Theodontius, who wrote on the wars of Troy, and is quoted by Servius on Aeneid, I, 28; and the fourteenth century author Domenico Bandini, who made an index for the Genealogiae, calls him "Teodontius Campanus diligens investigator poetici figmenti". Carlo Landi argued in his 1930 monograph Demogorgone that Boccaccio's Theodontius was a Campanian philosopher, from between the 9th and 11th centuries.

Theodontius provided Boccaccio with euhemeristic and naturalistic interpretations of mythology, and philosophic speculations about mythology. He quotes the (also lost) Greek historian Philochorus

Philochorus

Philochorus, of Athens, Greek historian during the 3rd century BC, , was a member of a priestly family. He was a seer and interpreter of signs, and a man of considerable influence....

. Most significantly, he is Boccaccio's source for the idea that all the gods were descended from Demogorgon

Demogorgon

Demogorgon, although often ascribed to Greek mythology, is actually attributed to a fourth-century scholar, imagined as the name of a pagan god or demon, associated with the underworld and envisaged as a powerful primordial being, whose very name had been taboo.-Etymology:The origins of the name...

, which Theodontius himself credited to Pronapides the Athenian.