PALEOBIOLOGY AND TAPHONOMY OF EXCEPTIONALLY PRESERVED PUTATIVE MACROALGAE FROM THE EDIACARAN ZUUN-ARTS BIOTA, WESTERN MONGOLIA

The first unequivocal evidence of complex multicellular life appears in the Ediacaran Period. Glimpses of life during this time can be seen in exceptionally preserved fossil deposits, which hold the key to a better understanding of the origins of multicellular life. One such fossil deposit is the recently discovered Burgess Shale-type (BST) Zuun-Arts Biota of Zavkhan Province, Mongolia. Study of the Zuun-Arts Biota is just beginning, but preliminary SEM-EDS and morphological data indicate at least two forms of putative macroalgae preserved as aluminosilicate films. The biota is preserved in a black shale and is dominated by one species of putative macroalgae, Chinggiskhaania bifurcate. The goals of this project are to test the hypotheses that 1) the Chinggiskhaania specimens are indeed macroalgae and 2) they are preserved as aluminosilicate films. In order to test these hypotheses, fieldwork has been conducted to collect more fossil specimens. Morphological data, including the width and length of all elements and branching angles of any branching specimens, will be collected in order to constrain the taxonomic affinity of Chinggiskhaania. Morphological analysis will be aided through photography of specimens under cross-polarized light, as well as light microscope observations. SEM-EDS analysis will be performed on a sub-set of at least 25 specimens of Chinggiskhaania in order to learn more about their mode of preservation. Preliminary morphological data including branching filaments, thallus-like morphology and basal attachment structures resembling a stipe and holdfast support a macroalgae interpretation for Chinggiskhaania. Preliminary SEM-EDS data indicate high concentrations of silicon and aluminum relative to other elements as well as local concentrations of carbon. This is consistent with preservation as aluminosilicate films, possibly the result of diagenetically altered carbon films. Preliminary data suggest that the results of this study will support both of the central hypotheses being tested.