"Dryophyllum is the most common plant fossil found in Hell Creek. It is a member of the walnut family, its form resembles the modern Hickory or Pecan trees (Carya), as does its foliage, with long serrated leaves. It is wind pollinated via long cylindrical flower clusters called catkins."
Dryophyllum subfalcatum belongs to the family Juglandaceae, the same family of walnuts, pecan and hickory. It is possible the Dryophyllum also produced edible nuts and, given it's abundance, it may have been an important food source in Hell Creek.