Zygadelphus aetheus gen. et sp. nov., an unusual fossil flower from mid-Cretaceous Myanmar amber

Abstract

The flower described here as Zygadelphus aetheus gen. et sp. nov. was obtained from amber mines in Myanmar, preserved in marine sedimentary deposits dating to the mid-Cretaceous Period, ca. 99 My in age. The perianth consists of ca. 10 spirally arranged tepals that vary in size and shape. The stigmatic tips of two styles are visible, the remainder of the gynoecium being hidden from view by the crowding of stamens and perianth parts toward the center of the flower. There is a whorl of 4 stamens, the anthers of which have the feature, probably unique among angiosperms, of possessing a small but complete accessory stamen arising as an appendage on their dorsal surface. Anthers of both types of stamens are bilocular and dehisce by dorsally hinged valves. Presence of pollen in the accessory anthers indicates that they functioned in reproduction. Under the assumption that the fossil is not merely a teratological mutant in an otherwise normal-flowered species, it is here given taxonomic status as representing a peculiar type of floral development, now extinct, that existed during an earlier stage of angiosperm evolution.