Paper No. 130-3
Presentation Time: 2:00 PM
SYNCHROTRON-BASED TOMOGRAPHIC EVALUATION OF EUMORPHOCYSTIS (DIPLOPORITA: ECHINODERMATA) AND ITS USE IN UNDERSTANDING MORPHOLOGY AND ONTOGENY
SHEFFIELD, Sarah L.1, BAUER, Jennifer E.1, SUMRALL, Colin D.2 and RAHMAN, Imran Alexander3, (1)Earth and Planetary Sciences, The University of Tennessee, 1621 Cumberland Ave, 602 Strong Hall, Knoxville, TN 37996-1410, (2)Department of Earth and Planetary Sciences, University of Tennessee, 1621 Cumberland Ave, 602 Strong Hall, Knoxville, TN 37996-1410, (3)Oxford University Museum of Natural History, Parks Road, Oxford, OX1 3PW, United Kingdom, ssheffi2@vols.utk.edu
The use of digital data in paleontology has opened numerous opportunities to learn more about the morphology of fossil organisms than has ever before been possible, leading to greater insight into deep evolutionary relationships and ontogenetic trends.
Eumorphocystis multiporata, an unusual diploporitan blastozoan echinoderm from the Upper Ordovician Bromide Formation of Oklahoma, USA was recently scanned using propagation-based phase-contrast synchrotron radiation X-ray tomographic microscopy at the TOMCAT beamline of the Swiss Light Source, Paul Scherrer Institut, Villigen, Switzerland. The fossil was scanned using an X-ray energy of 37 keV, 1001 projections and exposure time of 1000 ms, and the sample-to-detector propagation distance was set at 350 mm. The resulting images were stacked to examine morphological features through the specimen. The stacked images were then used to reconstruct external and internal morphologies of the specimen.
Eumorphocystis has unusual morphologies and plate growth that has made understanding the evolutionary relationships of this taxon difficult. The synchrotron scans of this specimen shed light on these morphologies; specifically, we focus on the plating of the arms and food groove construction; the addition of plates within the body wall; and the morphologies of the respiratory structures, diplopores (double pores).
This effort represents the first virtually reconstructed model of a diploporitan and suggests many future applications. Diploporita has recently been shown to be polyphyletic, indicating that the group-defining diplopore respiratory structures are convergent, appearing multiple times in the echinoderm tree of life. The morphology of diplopores are poorly understood at this time; this morphological interpretation of the diplopores of Eumorphocystis, can be compared to morphologies found in future diploporitan studies, to assess constructional similarities and differences across traditionally ascribed taxa. Further, better understanding of the arm and plate morphologies of Eumorphocystis will help elucidate deep-relationships of echinoderms.
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