Collinson, Margaret , Smith, Selena , Manchester, Steven , Wilde, Volker , Robson, Brittany , Ford, David , Marone, Federica , Fife, Julie , Stampanoni, Marco .
Paleobotanical applications of synchrotron X-ray tomography: an example from the fruit and seed flora of the Middle Eocene Messel Formation, Germany.
The Messel flora has been studied for several decades and is important for understanding Middle Eocene mid-latitude floras, biogeography, and plant evolution. A forthcoming monograph on fruits and seeds identifies over 65 species in 34 families but more than 50 other taxa are still unidentified. Synchrotron radiation X-ray tomographic microscopy (SRXTM) was used to survey a subset of unknown taxa to look for diagnostic features that might aid in identification. Strongly compressed specimens do not retain a high level of detail. Moderately compressed to relatively uncompressed three-dimensional specimens varied widely in the internal detail that was visualized. For many specimens, SRXTM was useful for showing the overall morphology, e.g.,visualizing the number of segments, or lengths and details of spines extending into the shale matrix. For one taxon, this has shown that the spines were not hooked and therefore there is no evidence of epizoochory in the Messel flora.Features such as locules or resin cavities were often visualized as well providing useful taxonomic information. Key taxonomic characters revealed with SRXTM supported recognition of new taxa, some of which are the earliest fossil representatives of modern genera (Pleiogynium, Anacardiaceae; Berchemia, Rhamnaceae). In addition, these can be digitally segmented to isolate a tissue layer of interest or produce virtual locule casts. For example, in Menispermaceae, fruits, endocarps, and locule casts are differentially preserved in fossil floras, and "virtual taphonomy" of these specimens might allow a better comparison among floras such as the Clarno Chert, London Clay, and Messel Oil Shale. A virtual locule cast of Paleosinomenium has been produced, but in practice, the amount of compression in Messel menisperms examined to date makes this difficult to apply. Fewer taxa (only four of 30 studied) retained consistent cellular detail, and it is not clear what the reason is for this differential preservation. Volkeria (Cyperaceae) fruits retained cellular detail in the mesocarp and basal plug. Seeds from a Decodon-like fruit (Lythraceae) show distinct layers with thin-walled cells visualized from the inner seed coat. Cellular detail in Crassivitisemen (Vitaceae) shows three layers of the pericarp including a thick central zone of thin-walled, equiaxial cells and a seed coat of multiple layers of small, closely packed, radially arranged elongate cells. The data from these SRXTM studies of Messel have been important both for plant systematics and for understanding further aspects of the paleoecology of the ancient Lake Messel.
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1 - Royal Holloway University of London, Dept. of Earth Sciences, Egham, TW20 0EX, UK
2 - University of Michigan, Dept. of Earth & Environmental Sciences, 2534 CC Little Building, 1100 N University Ave., Ann Arbor, MI, 48109, USA
3 - University Of Florida, Florida Museum Of Natural History, PO BOX 117800, Gainesville, FL, 32611, USA
4 - Senckenberg Forschungsinstitut und Naturmuseum, Frankfurt am Main, Germany
5 - Paul Scherrer Institut, Swiss Light Source, Villigen, Switzerland
synchrotron X-ray tomography (SRXTM).
Presentation Type: Oral Paper:Papers for Sections
Location: Union A/Hyatt
Date: Wednesday, July 11th, 2012
Time: 10:30 AM