The Ediacara fossil site at Nilpena, on the western margins of the Flinders Ranges in South Australia, was declared a National Heritage site for its palaeontological values in 2007. Our team is dedicated to conserving the fossils and the stratigraphic context on site as a natural Ediacaran laboratory for the study of the distribution of fossils in relationship to the rock strata, stratigraphic level and sedimentary tectonics. The site preserves assemblages of Ediacara organisms that inhabited the seafloor near fair-weather wave base and also in deeper water below storm wave base. In addition, large fronds and other three-dimensionally preserved fossils are preserved in massive sand flows within deep channels. Within a small area, geologists can see evidence of tidal flats where microbial mats trapped sand, offshore rippled delta tops preserving dense communities of bottom-living Ediacara animals and plants, deeper-water communities smothered by sand flows, and distorted remains of large frond, fan and disc-shaped organisms that were torn from shallow-marine seafloors and washed into submarine channels. By excavating and re-assembling successive fossil-bearing bedding surfaces we are able to study the ecological relationships of these organisms in successions on the margins of submarine channels and within the channels.

Since the Nilpena site has not suffered un-regulated collection it provides a unique window into the earliest communities of large marine organisms on Earth that can be compared with those in South East Newfoundland (Mistaken Point), England (Leicester), Namibia (Aar Farm) and NW Russia (the White Sea region). By preserving sites and fossil assemblages from these widely separated Ediacaran fossil sites we are beginning to make in-roads into understanding the apparently strange biology and anomalous global distribution of Ediacara organisms. In 2008, a joint study of Australian and Chinese Ediacara fossil assemblages revealed the first Ediacara species in common between these Ediacaran fossil settings. The discovery of the same Ediacara fossils in settings where the preservation is very different, opens a new window to interpretation of the palaeobiology of the Ediacara biota.

A more recent project is exploring the origins of segmented animals with jointed appendages (arthropods) by comparing the Early Cambrian unmineralized fossil lagerstätte at Emu Bay on Kangaroo Island with the putative Ediacara arthropod taxa at Nilpena. Large assemblages of Parvancorina and Spriggina are being compared with new trilobitomorph and shield-shaped taxa at Emu Bay.

References

Droser. M.L. and Gehling, J.G. 2008. Reproduction and synchronous aggregrate growth in a new Ediacaran tubular organism. Science319, 1660-1662.

Droser, M. L., Gehling, J.G. and Jensen, S.R. 2006. Assemblage palaeoecology of the Ediacara biota: The unabridged edition? Palaeogeography, Palaeoclimatology, Palaeoecology232, 131-147.

Gehling, J.G. and Narbonne. G.M. 2007. Spindle-shaped Ediacara fossils from the Mistaken Point assemblage, Avalon Zone, Newfoundland. Canadian Journal of Earth Sciences 44, 367-387.

Lin, J-P., Gon III, S.M., Gehling, J.G., Babcock, L.E., Zhao, Y-L., Zhang, X-L., Hu, S-X.Yuan, J-L., Yu, M-Y. & Peng, J. 2006. A Parvancorina-like arthropod from the Cambrian of South China. Historical Biology 18, 33-45.

Paterson, J.R., Jago, J.B., Gehling, J.G., García-Bellido, D.C., EdgecombeG.D. and Lee, M.S.Y. 2008. Early Cambrian arthropods from the Emu Bay Shale lagerstätte, South Australia. In: I.Rábano, R. Gozalo and D. García-Bellido (Eds.), Advances in trilobite research. Cuadernos del Museo Geominero, nº 9. Instituto Geológico y Minero de España, Madrid. pp1-7.

Peterson, K., Cotton, J.A., Gehling, J.G. and Pisani, D. 2008. MicroRNAs and the advent of vertebrate morphological complexity. Philos Trans R Soc Lond B Biol Sci.10.1098/rstb.2007.2233.

Zhu, M., Gehling, J.G., Xiao, S., Zhao, Y. and Droser, M.L. 2008. Eight-armed Ediacara fossil preserved in contrasting taphonomic windows from China and Australia. Geology 36, 867-870: doi: 10:1130/G25205A.1;2; 2 figures: Data Repository item 2008222.

Jim Gehling

Senior Research Scientist, Palaeontology

South Australian Museum

2008