Mindell, Randal , Karafit, Steven J. , Stockey, Ruth A. .
Bisexual Platanaceae flowers and inflorescences from the Late Cretaceous of Vancouver Island, Canada.
FOUR specimens of anatomically preserved platanaceous inflorescences have been found in marine nodules from the Late Cretaceous (Coniacian) Eden Main locality of the Nanaimo Group (Comox Formation) on Vancouver Island, British Columbia, Canada. The globose inflorescences are small (< 5 mm) and pedunculate with less than 30 flowers per inflorescence. At early stages of development, elongate and overarching tepals enclose the developing gynoecium and androecium. Later developmental stages show that individual flowers have at least two whorls of tepals that are fused towards the base. Each flower has a whorl of five free stamens with short filaments and sclerotic apical connective extensions. In situ tricolpate pollen is prolate and 11-13 μm in polar diameter, 8-9 μm in equatorial diameter. The stamens surround five short, conduplicate carpels with undifferentiated styles and broad, flat apices. A single ovule can often be observed in the ovary of these carpels. No trichomes are observed at the base of the carpels. The Eden Main fossils are similar in construction to other Cretaceous platanoids, having the pentamerous arrangement that dominates the fossil record and the short carpels known in the earliest pistillate flowers of Platanaceae. The repeated co-occurrence of stamens and carpels in the same flowers of the Eden Main inflorescences is the first clear evidence of functional bisexuality in flowers of fossil Platanaceae and shows that this feature was present in platanoids as late as the Coniacian.
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1 - University of Alberta, Department of Biological Sciences, Biological Sciences Centre, Cw 405, Edmonton, Alberta, T6G 2E9, Canada
Presentation Type: Oral Paper:Papers for Sections
Date: Monday, July 31st, 2006
Time: 1:45 PM