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The below mentioned article provides short notes on the fossil members of Ginkgoaceae.
Sphenobaiera, Ginkgoites, Baiera, Arctobaiera, Windwardia and Eretmophyllum are the fossil members of Ginkgoaceae according to Sporne (1965). In growth habit, all fossil members of Ginkgoaceae resembled Ginkgo biloba and possessed long and short shoots. Most of them are known only from their leaves.
The leaves of Windwardia and Arctobaiera (Fig. 10.27 A,B) were strap-shaped with few veins while that of Eretmophyllum were fan-shaped with several veins. The leaves of Baiera and Ginkgoites (Fig 10.27 C,D) resembled greatly with that of Ginkgo biloba in shape and also had a distinct petiole.
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Petiole was absent in the leaves of other fossil Ginkgoaceae genera. Leaves of Sphenobaiera were circular in outline, dichotomously branched and resembled Trichopitys heteromorpha of family Trichopityaceae of Ginkgoales. All fossil Ginkgoaceae leaves had strictly dichotomous open venation.
Regarding different genera, known only from their leaves, Sporne (1965) has, however, rightly cautioned that “so far as the fossil Ginkgoales are concerned, this should serve as a warning against putting too much reliance on statements about genera that are based solely on leaves”.
Regarding some of the other known details of some fossil Ginkgoaceae, Sphenobaiera furcate had clusters of microsporangia at the branched tips of a bifurcating axis. Such male axes were present on short shoots along with the dichotomously branched leaves.
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In Baiera muensteriana, some catkin-like structures were associated with leaves. Short lateral branches of these catkin like structures terminated into 10-12 reflexed microsporangia (Fig. 10.28 A,B). Andrews (1961) also described some other fossil members of Ginkgoaceae.
These include Saportaea nervosa (described from Permian of Shansi in China), Ginkgodium nathorsti (with spoon-shaped, shortly petioled leaves), Dichophyllum moorei (with characteristic branching pattern lacking any distinction into main axis and leaves), Ginkgo adiantoides (with kidney-shaped leaves), G. digitata (with deeply dissected wedge-shaped lamina) and G. lamariensis (wedge-shaped, slightly notched leaves).
