He was putatively either a pupil or follower of Giotto, and painted frescoes in the churches of San Domenico and the Franciscans in his native city.
He is considered the founder of the Forlivese school of art in the early Renaissance.
A Madonna delle Grazie in the Forli Cathedral is attributed to Guglielmo.
Guglielmo is said to have been born sometime in the first half of the 14th century and continued to paint until 1408.
[1] According to Vasari, in Forli he was a pupil of the painter Vespignano, who like Giotto died circa 1336.