He was the supposed author of a chronicle, now called the Chronicon of Pseudo-Dexter. It was in fact a forgery, one of a number of Román de la Higuera (1538-1611) including the continuation attributed to Marcus Maximus, as scholars now agree. The suspect authorship has been widely known since the work of the Spanish bibliographer Nicolás Antonio, the Censura de historias fabulosas, published in 1742.
Doubts were already cast on these falsos chronicones before 1600, but controversy continued late into the eighteenth century. The Cistercian François de Bivar (Bivarius) published a commentary and strong defence (Lyon, 1627). Later references to the Chronicon as genuine abound.