Smith, Selena Y. , Collinson, Margaret E. , Simpson, David A. , Rudall, Paula, J. , Marone, Federica , Stampanoni, Marco .
Ancient Cyperaceae: evidence for widespread tropical forest sedges from the Eocene of Europe.
The sedges (Cyperaceae) are an economically and ecologically important monocot family dating back at least to the Paleocene. While modern genera are mostly unknown until the Oligocene, several extinct taxa are recognized as the earliest sedges. Their affinities have been unclear until now, as they are found as isolated, often abraded, fruits or endocarps with limited diagnostic characters. Exceptionally preserved sedge fossils from the Middle Eocene of Messel, Germany have yielded more characters for identification. Fossil cyperacean infructescences with in situ pollen are recognized for the first time and show features of the early-divergent mapanioid sedges. Pollen was studied using fluorescence microscopy, SEM and TEM. Pollen grains are spherical with a single distinct ulcerate aperture and prominent orbicules, and closely resemble those of tribe Hypolytreae. Fruit anatomy of numerous fossil and modern sedge species was examined using synchrotron radiation X-ray tomographic microscopy. Comparisons suggest that the closest affinities are with extant Hypolytrum and Mapania, and with the fossil genus Caricoidea, a typical Eocene sedge that was widespread across Eurasia. Without the additional characters from the infructescence and pollen, the Messel fruits would have been placed in the extinct genus Caricoidea; however, they represent a new genus. Similarities of fruit structure suggest that Caricoidea was also a mapanoid sedge. Mapanioid sedges are found today in tropical wet forests and swamps, unlike many modern sedges occupying open habitats, suggesting that early sedges occupied a similar habitat and were not precursors to open grassland vegetation.
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1 - University of Michigan, Museum of Paleontology, 1109 Geddes Road, Ann Arbor, MI, 48109, USA
2 - Royal Holloway University of London, Department of Earth Sciences, Egham, Surrey, TW20 0EX, UK
3 - Royal Botanic Gardens, Kew, Herbarium, Richmond, Surrey, TW9 3DS, UK
4 - Royal Botanic Gardens, Kew, Jodrell Laboratory, Richmond, Surrey, TW9 3AB, United Kingdom
5 - Paul Scherrer Institut, Swiss Light Source, CH-5232 Villigen, Switzerland
synchrotron radiation X-ray microtomography.
Presentation Type: Oral Paper:Papers for BSA Sections
Location: Superior A/Cliff Lodge - Level C
Date: Wednesday, July 29th, 2009
Time: 1:30 PM