Fortunatianus, an African by birth, bishop of Aquilia during the reign of Constantius, composed brief Commentaries on the gospels arranged by chapters, written in a rustic style, and is held in detestation because, when Liberius bishop of Rome was driven into exile for the faith, he was induced by the urgency of Fortunatianus to subscribe to heresy.According to W.H. Fremantle (in Smith & Wace, Dictionary of Christian Biography, vol. 2, p. 550) 'He persuaded Liberius, the bishop of Rome, who was ready to go into exile for his faith, that he might properly subscribe the formula of the council of Sirmium; and he even went so far as to consent to the condemnation passed upon Athanasius in the council of Milan.'
So Fortunatianus was obviously a bit Arian in Christology. But Jerome did value his commentaries, describing them in a letter requesting that Paulus of Concordia send him a copy, as 'the pearl of the Gospel, the words of the Lord, pure words, even as the silver which from this earth is tried, and purified seven times in the fire' (Jerome, Ep. X of AD 374, alluding to Matt 13.46; Ps 12.7).
Only a couple of fragments survive of Fortunatianus' commentary, .... or so we thought. Recently Lukas Dorfbauer has identified an anonymous commentary on the gospels (MS Köln, Erzbischöfliche Diözesan- und Dombibl. 17) as a copy of this commentary: "Thus, Fortunatianus’ work becomes the apparently oldest commentary on the Gospels written in the Latin West which is still extant; it amplifies our knowledge of ancient Christianity and its literature in many respects." (CSEL web page)
For details see L. J. Dorfbauer, Der Evangelienkommentar des Bischofs Fortunatian von Aquileia (Mitte 4. Jh.). Ein Neufund auf dem Gebiet der patristischen Literatur, Wiener Studien 126 (2013), 177-198.
here. (HT: Roger Pearse [with more details from Quasten]) [Looks like further confirmation of Head's rule.]