Two of the major stylistic elements found in late medieval Italian art are exemplified in the work of Nicola and Giovanni Pisano. Nicolo worked in the classical style, as seen in the figures in his Annunciation,Nativity, and Adoration of the Shepherds relief panel in the bapistry pulpet in Pisa, which are taken directly from those found on Roman sarcophigi. Nicolo's son, Giovanni worked in the French Gothic style characterized by an emotionalism and sinuosity not present in his father's work. His Annunciation panel the pulpet of St. Andrea in Pisola exemplifies this style. However, I have seen this same active depiction of figures in some of the Roman sarcophghi in the Uffizi, so I am not sure the distinction Gardner is making is a valid one.
A third element in the art of this period is the Italo-Byzantine style as seen in the work of Buonaventura Berlinghileri, as in the St. Francis Alterpiece.
Gardner suggests the source for this work may be a Byzantine illuminated manuscript, and indeed it appears to hearken back to an earlier era.