Within the form classification system used in paleobotany, Williamsonia is used to refer to female seed cones, which are associated with plants that also bore the male flower-like reproductive structure Weltrichia.

[7] In at least some species, the cones increased in size during maturation, which might reflect the transformation of the interseminal scales into a fleshy coating possibly used to attract seed dispersers.

[8] Kimuriella is thought to have been a divaricately branching, low growing shrub with a maximum height of 2–3 metres, with a growth form similar to that of Wielandiella, while Williamsonia gigas may have been more cycad-like.

[11] William Carruthers proposed the name Williamsonia in 1870, with the type species being W. gigas from the Middle Jurassic of England.

However, later authors beginning with Tom Harris's 1969 publication The Yorkshire Jurassic Flora used Williamsonia to refer to the ovulate reproductive organs.