BISEXUAL FLOWERS FROM THE CONIACIAN (LATE CRETACEOUS) OF VANCOUVER ISLAND, CANADA: AMBIPLATANUS WASHINGTONENSIS GEN. ET SP. NOV. (PLATANACEAE).

Premise of research. Anatomically preserved platanaceous inflorescences have been found in rocks of Late Cretaceous (Coniacian) age at the Eden Main locality on Vancouver Island, British Columbia, Canada. Methodology. Specimens occur in calcium carbonate concretions near the base of the Nanaimo Group (Comox Formation) and are studied with the cellulose acetate peel technique and SEM. Pivotal results. Inflorescences are small (<5 mm), pedunculate heads, with fewer than 30 ?flowers per inflorescence. Both bisexual and unisexual flowers are present on the same inflorescence. Elongate and overarching tepals enclose the developing gynoecium and androecium at early stages of development. More mature specimens have individual flowers with at least two whorls of tepals fused toward the base. Flowers have a whorl of five free stamens, each with short filaments and a sclerotic apical connective extension. In situ pollen is small, prolate, tricolpate, 11-13 μm in polar diameter, and 8-9 μm in equatorial diameter. In flowers where it can be observed, the staminal whorl encloses five short, conduplicate, glabrous carpels lacking differentiated styles but bearing broad, flat apices. The ovary of these carpels is occupied by a single ovule. Conclusions. While the Eden Main specimens display a five-parted gynoecial arrangement common in the pistillate flowers of other Cretaceous platanoids, Ambiplatanus washingtonensis gen. et sp. nov. provides the first fossil evidence of functional bisexuality in fossil Platanaceae. [ABSTRACT FROM AUTHOR]