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Abstract Detail


Paleobotanical Section

Strömberg, Caroline A. E. [1], Wing, Scott L. [2], Hickey, L. J. [3], Morey, Amy [2].

New perspectives on the Late Cretaceous Big Cedar Ridge flora, Wyoming.

The plant fossils that make up the early Maastrichtian Big Cedar Ridge flora of the Meeteetse Formation, Wyoming, are preserved in situ at the base of a bentonitic ash bed exposed over a 4 km outcrop. Because of its unusual preservation, the flora provides a landscape-scale picture of vegetation at a particular moment in geologic time. In particular, herbs, which are rarely preserved in the fossil record, appear to be well represented. In contrast, the majority of the Late Cretaceous compression fossil record tends to reflect selected parts of the landscape (e.g., the riparian zone) and of the vegetation (e.g., trees). Previous work at Big Cedar Ridge has revealed a highly diverse flora in which the majority of taxa are non-monocotyledonous angiosperms. Recent collecting efforts and comprehensive revision and description of the Big Cedar Ridge morphotypes confirm this conclusion, and provide a more detailed understanding of the systematic and morphological make-up of the flora. The current number of recognized vegetative plant morphotypes at Big Cedar Ridge is ~150, encompassing one bryophyte, one lycopsid, 28 ferns, ten conifers, six cycads, ten monocotyledons, and at least 91 non-monocotyledonous angiosperms, of which 26 have entire margins and 67 toothed margins. Many of the non-monocotyledonous angiosperms display leaf features typical of herbaceous plants or scramblers, e.g., cordate or funnel-shaped bases, poorly organized venation, and highly dissected laminae. In addition, the vast majority are <10 cm long, in striking contrast to the large, relatively complete fern, cycad, and palm leaves preserved in the same deposit. Preliminary systematic work on the non-monocot angiosperm leaf types indicates that many of them are magnoliids (sensu lato), or lower eudicotyledons and lower core eudicotyledons, as recognized in the APGII phylogeny, although eurosids are present.


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1 - University of Washington, Department of Biology & Burke Museum, Box 351800, 24 Kincaid Hall, Seattle, WA, 98195, USA
2 - National Museum of Natural History, Smithsonian Institution, Department of Paleobiology, Mrc 121, Washington, DC, 20560, USA
3 - Yale University, Department of Geology & Geophysics, Yale Station, P.O. Box 208109, New Haven, Connecticut, 06520-8109, USA

Keywords:
Maastrichtian
Cretaceous
paleoecology
early angiosperms
Wyoming
leaf morphology.

Presentation Type: Poster:Posters for Sections
Session: P
Location: Ball Room & Party Room/SUB
Date: Monday, July 28th, 2008
Time: 12:30 PM
Number: PPB001
Abstract ID:607


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