Hostname: page-component-77c89778f8-7drxs Total loading time: 0 Render date: 2024-07-17T07:06:29.182Z Has data issue: false hasContentIssue false
  • English
  • Français

The Paleoproterozoic megascopic Stirling biota

Published online by Cambridge University Press:  20 May 2016

Stefan Bengtson ,
Birger Rasmussen  and
Bryan Krapež
Stefan Bengtson
Affiliation:
Department of Palaeozoology, Swedish Museum of Natural History, Box 50007, SE-104 05 Stockholm, Sweden. E-mail: [email protected]
Birger Rasmussen
Affiliation:
School of Earth and Geographical Sciences, The University of Western Australia, Crawley 6009, Western Australia, Australia. E-mail: [email protected] and [email protected]
Bryan Krapež
Affiliation:
School of Earth and Geographical Sciences, The University of Western Australia, Crawley 6009, Western Australia, Australia. E-mail: [email protected] and [email protected]
Get access Rights & Permissions [Opens in a new window]

Abstract

The 2.0–1.8-billion-year-old Stirling Range Formation in southwestern Australia preserves the deposits of a siliciclastic shoreline formed under the influence of storms, longshore currents, and tidal currents. Sandstones contain a megascopic fossil biota represented by discoidal fossils similar to the Ediacaran Aspidella Billings, 1872, as well as ridge pairs preserved in positive hyporelief on the soles of channel-fill sandstones bounded by mud drapes. The ridges run parallel or nearly parallel for most of their length, meeting in a closed loop at one end and opening with a slight divergence at the opposite end. The ridges are interpreted as casts of sediment-laden mucus strings formed by the movement of multicellular or syncytial organisms along a muddy surface. The taxa Myxomitodes stirlingensis n. igen., n. isp., are introduced for these traces. The Stirling biota was roughly coeval with other presumed multicellular eukaryotes appearing after a long period of profound environmental changes involving a rise in ambient oxygen levels, similar to that which preceded the Cambrian explosion. The failure of multicellular life to diversify during most of the Proterozoic may be due to environmental constraints related to the comparatively low level of oxidation of the world oceans.

Type
Articles
Information
Paleobiology , Volume 33 , Issue 3 , Summer 2007 , pp. 351 - 381
Copyright
Copyright © The Paleontological Society

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Literature Cited

Aharon, P. 2005. Redox stratification and anoxia of the early Precambrian oceans: implications for carbon isotope excursions and oxidation events. Precambrian Research 137: 207–222.Google Scholar
Anbar, A. D. and Knoll, A. H. 2002. Proterozoic ocean chemistry and evolution: a bioinorganic bridge? Science 297: 1137–1142.Google Scholar
Aris-Brosou, S. and Yang, Z. 2002. Effects of models of rate evolution on estimation of divergence dates with special reference to the metazoan 18S ribosomal RNA phylogeny. Systematic Biology 51: 703–714.Google Scholar
Arnold, G. L., Anbar, A. D., Barling, J., and Lyons, T. W. 2004. Molybdenum isotope evidence for widespread anoxia in mid-Proterozoic oceans. Science 304: 87–90.Google Scholar
Ayala, F. J. 1999. Molecular clock mirages. BioEssays 21: 71–75.Google Scholar
Ayala, F. J., Rzhetsky, A., and Ayala, F. J. 1998. Origin of the metazoan phyla: molecular clocks confirm paleontological estimates. Proceedings of the National Academy of Sciences USA 95: 606–611.Google Scholar
Baldauf, S. L., Roger, A. J., Wenk-Siefert, I., and Doolittle, W. F. 2000. A kingdom-level phylogeny of eukaryotes based on combined protein data. Science 290: 972–977.Google Scholar
Beeson, J. 1991. A field and experimental study of structures in the Albany Mobile Belt, Western Australia. Ph.D. thesis. University of Western Australia, Perth.Google Scholar
Bengtson, S. 2002. Origins and early evolution of predation. In Kowalewski, M. and Kelley, P. H., eds. The fossil record of predation. Paleontological Society Special Papers 8: 289–317.Google Scholar
Beninger, P. G., Lynn, J. W., Dietz, T. H., and Silverman, H. 1997. Mucociliary transport in living tissue: the two-layer model confirmed in the mussel L. Biological Bulletin 193: 4–7.Google Scholar
Bjerrum, C. J. and Canfield, D. E. 2002. Ocean productivity before about 1.9 Gyr ago limited by phosphorous adsorption onto iron oxides. Nature 417: 159–162.Google Scholar
Blair, J. E. and Hedges, S. B. 2005. Molecular clocks do not support the Cambrian explosion. Molecular Biology and Evolution 22: 387–390.Google Scholar
Bölücek, C. and Ilhan, B. 2006. A survey of pyritised animal, plant, and trace fossils and concretionary pyrites, Germav Formation, southeastern Turkey. Comptes Rendus Geoscience 338: 161–171.Google Scholar
Bonner, J. T. 2000. First signals: the evolution of development. Princeton University Press, Princeton, N.J.Google Scholar
Boulter, C. A. 1979. On the production of two inclined cleavages during a single folding event; Stirling Range, S.W. Australia. Journal of Structural Geology 1: 207–219.Google Scholar
Bourlat, S. J., Nielsen, C., Lockyer, A. E., Littlewood, D. T J., and Telford, M. J. 2003. is a deuterostome that eats molluscs. Nature 424: 925–928.Google Scholar
Breen, E. J., Vardy, P. H., and Williams, K. L. 1987. Movement of the multicellular slug stage of : an analytical approach. Development 101: 313–3322.Google Scholar
Breyer, J. A., Busbey, A. B., Hanson, R. E., and Roy, E. C I. 1995. Possible new evidence for the origin of metazoans prior to 1 Ga: sediment-filled tubes from the Mesoproterozoic Allamoore Formation, Trans-Pecos Texas. Geology 23: 269–272.Google Scholar
Brocks, J. J., Logan, G. A., Buick, R., and Summons, R. E. 1999. Archean molecular fossils and the early rise of eukaryotes. Science 285: 1033–1036.Google Scholar
Bromley, R. 1996. Trace fossils, 2d ed. Chapman and Hall, London.Google Scholar
Buatois, L. A., Mángano, M. G., Maples, C. G., and Lanier, W. P. 1998. Taxonomic reassessment of the ichnogenus and additional examples from the Carboniferous of Kansas, U.S.A. Ichnos 5: 287–302.Google Scholar
Budd, G. E. and Jensen, S. 2000. A critical reappraisal of the fossil record of the bilaterian phyla. Biological Reviews 75: 253–295.Google Scholar
Budd, G. E. and Jensen, S. 2003. The limitations of the fossil record and the dating of the origin of the Bilateria. pp. 166–189in Donoghue, P. C. J., ed. Telling the evolutionary time: molecular clocks and the fossil record. Taylor and Francis, London.Google Scholar
Butterfield, N. J. 2000. n. gen., n. sp.: implications for the evolution of sex, multicellularity, and the Mesoproterozoic/Neoproterozoic radiation of eukaryotes. Paleobiology 26: 386–404.Google Scholar
Butterfield, N. J. 2004. A vaucheriacean alga from the middle Neoproterozoic of Spitsbergen: implications for the evolution of Proterozoic eukaryotes and the Cambrian explosion. Paleobiology 30: 231–252.Google Scholar
Canfield, D. E. and Raiswell, R. 1991. Pyrite formation and fossil preservation. pp. 337–387in Allison, P. A., and Briggs, D. E. G., eds. Taphonomy: releasing the data locked in the fossil record. Plenum, New York.Google Scholar
Canfield, D. E. and Teske, A. 1996. Late Proterozoic rise in atmospheric oxygen concentration inferred from phylogenetic and sulphur-isotope studies. Nature 382: 127–132.Google Scholar
Cavalier-Smith, T. 1987. The origin of eukaryote and archaebacterial cells. Annals of the New York Academy of Sciences 503: 17–54.Google Scholar
Cavender, J. S. 1990. Phylum Dictyostelida. pp. 88–101in Margulis, et al. 1990.Google Scholar
Clemmey, H. 1976. World's oldest animal traces. Nature 261: 576–578.Google Scholar
Cloud, P. 1973. Pseudofossils: a plea for caution. Geology 1: 123–127.Google Scholar
Collins, A. G., Lipps, J. H., and Valentine, J. W. 2000. Modern mucociliary creeping trails and the bodyplans of Neoproterozoic trace-makers. Paleobiology 26: 47–55.Google Scholar
Morris, S. Conway 2002. Ancient animals or something else entirely? Science 298: 57–58.Google Scholar
Morris, S. Conway 2006. Darwin's dilemma: the realities of the Cambrian ‘explosion.’. Philosophical Transactions of the Royal Society of London B 361: 1069–1083.Google Scholar
Corliss, J. O. 1990. Phylum Zoomastigina. Class Opalinata. pp. 239–245in Margulis, et al. 1990.Google Scholar
Cruse, T. 1991. The sedimentology, depositional environment and Ediacaran fauna of the Stirling Range Formation, Western Australia. B. Sc. Honours thesis. University of Western Australia, Perth.Google Scholar
Cruse, T. and Harris, L. B. 1994. Ediacaran fossils from the Stirling Range Formation, Western Australia. Precambrian Research 67: (1-2). 1–10.Google Scholar
Cruse, T., Harris, L. B., and Rasmussen, B. 1993. The discovery of Ediacaran trace and body fossils in the Stirling Range Formation, Western Australia: implications for sedimentation and deformation during the Pan-African orogenic cycle. Australian Journal of Earth Sciences 40: 293–296.Google Scholar
Curds, C. R., Gates, M. A., and Roberts, D. M. 1983. British and other freshwater ciliated Protozoa, Part 2. Ciliophora: Oligohymenophora and Polyhymenophora keys and notes for the identification of the free-living genera. Cambridge University Press, Cambridge.Google Scholar
Davies, M. S. and Cliffe, E. J. 2000. Adsorption of metals in seawater to limpet () pedal mucus. Bulletin of Environmental Contamination and Toxicology 64: 228–264.Google Scholar
Davies, M. S. and Hawkins, S. J. 1998. Mucus from marine molluscs. Advances in Marine Biology 34: 1–71.Google Scholar
Douzery, E. J P., Snell, E. A., Bapteste, E., Delsuc, F., and Philippe, H. 2004. The timing of eukaryotic evolution: does a relaxed molecular clock reconcile proteins and fossils? Proceedings of the National Academy of Sciences USA 101: 15386–15391.Google Scholar
Droser, M. L., Jensen, S., and Gehling, J. G. 2002. Trace fossils and substrates of the terminal Proterozoic-Cambrian transition: implications for the record of early bilaterians and sediment mixing. Proceedings of the National Academy of Sciences USA 99: 12572–12576.Google Scholar
Du, R. and Tian, L. 1985. Discovery and preliminary study of mega-alga from the Qingbaikou System of the Yanshan Mountain area. Acta Geologica Sinica 1985: 183–190.Google Scholar
Dupraz, C., Visscher, P. T., Baumgartner, L. K., and Reid, R. P. 2004. Microbe-mineral interactions: early carbonate precipitation in a hypersaline lake (Eleuthera Island, Bahamas). Sedimentology 51: 745–765.Google Scholar
Ehlers, U. and Sopott-Ehlers, B. 1997. Ultrastructure of the subepidermal musculature of , the adelphotaxon of the Bilateria. Zoomorphology 117: 71–79.Google Scholar
Gehling, J. G., Narbonne, G. M., and Anderson, M. M. 2000. The first named Ediacaran body fossil; . Palaeontology 43: 427–456.Google Scholar
Gerdes, G., Klenke, T., and Noffke, N. 2000. Microbial signatures in peritidal siliciclastic sediments: a catalogue. Sedimentology 47: 279–308.Google Scholar
Glaessner, M. F. 1969. Trace fossils from the Precambrian and basal Cambrian. Lethaia 2: 369–393.Google Scholar
Gräf, W. and Schmitt, J. 1979. Wassermyxobakterien () und die Ordnung “Myxobacterales.”. Zentralblatt für Bakteriologie, Abteilung 1 169: 240–252.Google Scholar
Graur, D. and Martin, W. 2004. Reading the entrails of chickens: molecular timescales of evolution and the illusion of precision. Trends in Genetics 20: 80–86.Google Scholar
Han, T-M. and Runnegar, B. 1992. Megascopic eukaryotic algae from the 2.1 billion-year-old Negaunee Iron-Formation, Michigan. Science 257: 232–235.Google Scholar
Harris, L. B. 1994. Neoproterozoic sinistral displacement along the Darling Mobile Belt, Western Australia, during Gondwanaland assembly. Journal of the Geological Society, London 151: 901–904.Google Scholar
Harris, L. B. and Beeson, J. 1993. Gondwanaland significance of Lower Palaeozoic deformation in central India and SW Western Australia. Journal of the Geological Society, London 150: 811–814.Google Scholar
Harris, L. B. and Li, Z-X. 1995. Palaeomagnetic dating and tectonic significance of dolerite intrusions in the Albany Mobile Belt, Western Australia. Earth and Planetary Science Letters 131: 143–164.Google Scholar
Hedges, S. B., Chen, H., Kumar, S., Wang, D. Y-C., Thompson, A. S., and Watanabe, H. 2001. A genomic timescale for the origin of eukaryotes. BMC Evolutionary Biology 1 (4). [Published online 12 September 2001.].Google Scholar
Hoffman, P. F., Kaufman, A. J., Halverson, G. P., and Schrag, D. P. 1998. A Neoproterozoic Snowball Earth. Science 281: 1342–1346.Google Scholar
Hofmann, H. J. 1985. Precambrian carbonaceous megafossils. pp. 20–33in Toomey, D. F. and Nitecki, M. H., eds. Paleoalgology: contemporary research and applications. Springer, Berlin.Google Scholar
Hofmann, H. J. 1994. Proterozoic carbonaceous compression (“metaphytes” and “worms”). pp. 342–357in Bengtson, S., ed. Early life on Earth. Columbia University Press, New York.Google Scholar
Hofmann, H. J. and Chen, J. 1981. Carbonaceous megafossils from the Precambrian (1800 Ma) near Jixian, northern China. Canadian Journal of Earth Sciences 18: 443–447.Google Scholar
Hofmann, H. J., Mountjoy, E. W., and Teitz, M. W. 1991. Ediacaran fossils and dubiofossils, Miette Group of Mount Fitzwilliam area, British Columbia. Canadian Journal of Earth Sciences 28: 1541–1552.Google Scholar
International Commission on Zoological Nomenclature. 1999. Code of zoological nomenclature, 4th ed. International Trust for Zoological Nomenclature, London.Google Scholar
Israelsson, O. 1997. ['s molluscan relatives] … and molluscan embryogenesis. Nature 390: 32.Google Scholar
Israelsson, O. 1999. New light on the enigmatic (phylum uncertain): ontogeny and phylogeny. Proceedings of the Royal Society of London B 266: 835–841.Google Scholar
Jensen, S. 1997. Trace fossils from the Lower Cambrian Mickwitzia sandstone, south-central Sweden. Fossils and Strata 42: 1–111.Google Scholar
Jensen, S. 2003. The Proterozoic and earliest Cambrian trace fossil record; patterns, problems and perspectives. Integrative and Comparative Biology 43: 219–228.Google Scholar
Jensen, S., Droser, M. L., and Gehling, J. G. 2005. Trace fossil preservation and the early evolution of animals. Palaeogeography, Palaeoclimatology, Palaeoecology 220: 19–29.Google Scholar
Kauffman, E. G. and Steidtmann, J. R. 1981. Are these the oldest metazoan trace fossils? Journal of Paleontology 55: 923–947.Google Scholar
Kirschvink, J. L. 1992. Late Proterozoic low-latitude global glaciation: the Snowball Earth. pp. 51–52in Schopf, J. W. and Klein, C., eds. The Proterozoic biosphere: a multidisciplinary study. Cambridge University Press, Cambridge.Google Scholar
Kirschvink, J. L., Gaidos, E. J., Bertani, L. E., Beukes, N. J., Gutzmer, J., Maepa, L. N., and Steinberger, R. E. 2000. Paleoproterozoic snowball Earth: extreme climatic and geochemical global change and its biological consequences. Proceedings of the National Academy of Sciences USA 97: 1400–1405.Google Scholar
Kitazato, H. 1988. Locomotion of some benthic foraminifera in and on sediments. Journal of Foraminiferal Research 18: 344–349.Google Scholar
Knoll, A. H. 1994. Proterozoic and Early Cambrian protists: evidence for accelerating evolutionary tempo. Proceedings of the National Academy of Sciences USA 91: 6743–6750.Google Scholar
Książkiewicz, M. 1974. Trace fossils in the flysch of the Polish Carpathians. Palaeontologia Polonica 36: 1–208.Google Scholar
Levin, L. 1994. Paleoecology and ecology of xenophyophores. Palaios 9: 32–41.Google Scholar
Lom, J. 1990. Phylum Myxozoa. pp. 36–52in Margulis, et al. 1990.Google Scholar
Lucus, A. and Douglas, L. C. 1934. Principles underlying ciliary activity in the respiratory tract. Archives of Otolaryngology 20: 518–541.Google Scholar
Lundin, K. 2000. Xenoturbella: a creature of contradiction. Fauna och Flora 95: 44–48.Google Scholar
Marée, A. F M. and Hogeweg, P. 2001. How amoeboids self-organize into a fruiting body: multicellular coordination in . Proceedings of the National Academy of Sciences USA 98: 3879–3883.Google Scholar
Margulis, L., Corliss, J. O., Melkonian, M., and Chapman, D. J. eds. 1990. Handbook of Protoctista. Jones and Bartlett, Boston.Google Scholar
Martin, G. G. 1978. Ciliary gliding in lower invertebrates. Zoomorphologie 91: 249–261.Google Scholar
Muhling, P. C. and Brakel, A. T. 1985. Mount Barker-Albany 1:250000 geological series—Explanatory notes. Geological Society of Western Australia, Perth.Google Scholar
Norén, M. and Jondelius, U. 1997. 's molluscan relatives. Nature 390: 31–32.Google Scholar
Otsuka, J. and Sugaya, N. 2003. Advanced formulation of base pair changes in the stem regions of ribosomal RNAs; its application to mitochondrial rRNAs for resolving the phylogeny of animals. Journal of Theoretical Biology 222: 447–460.Google Scholar
Palsson, E. and Othmer, H. G. 2000. A model for individual and collective cell movement in . Proceedings of the National Academy of Sciences USA 97: 10448–10453.Google Scholar
Pawlowski, J., Holzmann, M., Berney, C., Fahrni, J., Gooday, A. J., Cedhagen, T., Habura, A., and Bowser, S. S. 2003. The evolution of early Foraminifera. Proceedings of the National Academy of Sciences USA 100: 11494–11498.Google Scholar
Pedersen, K. J. and Pedersen, L. R. 1986. Fine structural observations on the extracellular matrix (ECM) of Westblad, 1949. Acta Zoologica 72: 181–201.Google Scholar
Peterson, K. J., Lyons, J. B., Nowak, K. S., Takacs, C. M., Wargo, M. J., and McPeek, M. A. 2004. Estimating metazoan divergence times with a molecular clock. Proceedings of the National Academy of Sciences USA 101: 6536–6541.Google Scholar
Porter, S. and Knoll, A. H. 2000. Testate amoebae in the Neoproterozoic Era: evidence from vase-shaped microfossils in the Chuar Group, Grand Canyon. Paleobiology 26: 360–385.Google Scholar
Raikova, O. I., Reuter, M., Jondelius, U., and Gustafsson, M. K S. 2000. An immunocytochemical and ultrastructural study of the nervous and muscular systems of (Bilateria inc. sed). Zoomorphology 120: 107–118.Google Scholar
Rasmussen, B. and Fletcher, I. R. 2004. Zirconolite: a new U-Pb chronometer for mafic igneous rocks. Geology 32: 785–788.Google Scholar
Rasmussen, B., Bengtson, S., Fletcher, I. R., and McNaughton, N. 2002a. Discoidal impressions and trace-like fossils more than 1200 million years old. Science 296: 1112–1115.Google Scholar
Rasmussen, B., Bengtson, S., Fletcher, I. R., and McNaughton, N. 2002b. Ancient animals or something else entirely? Response. Science 298: 58–59.Google Scholar
Rasmussen, B., Bose, P. K., Sarkar, S., Banerjee, S., Fletcher, I. R., and McNaughton, N. J. 2002c. 1.6 Ga U-Pb zircon age for the Chorhat Sandstone, lower Vindhyan, India: Possible implications for early evolution of animals. Geology 30: 103–106.Google Scholar
Rasmussen, B., Fletcher, I. R., Bengtson, S., and McNaughton, N. 2004. SHRIMP U-Pb dating of diagenetic xenotime in the Stirling Range Formation, Western Australia: 1.8 billion year minimum age for the Stirling biota. Precambrian Research 133: 329–337.Google Scholar
Rauprich, O., Matsushita, M., Weijer, C. J., Siegert, F., Esipov, S. E., and Shapiro, J. A. 1996. Periodic phenomena in swarm colony development. Journal of Bacteriology 178: 6525–6538.Google Scholar
Ray, J. S., Martin, M. W., Veizer, J., and Bowring, S. A. 2002. U-Pb zircon dating and Sr isotope systematics of the Vindhyan Supergroup, India. Geology 30: 131–134.Google Scholar
Reisinger, E. 1960. Was ist ? Zeitschrift für wissenschaftliche Zoologie 164: 188–198.Google Scholar
Riemann, F. and Helmke, E. 2002. Symbiotic relations of sediment-agglutinating nematodes and bacteria in detrital habitats: the enzyme-sharing concept. Marine Ecology 23: 93–113.Google Scholar
Rokas, A., Krüger, D., and Carroll, S. B. 2005. Animal evolution and the molecular signature of radiations compressed in time. Science 310: 1933–1938.Google Scholar
Schieber, J. 1998. Possible indicators of microbial mat deposits in shales and sandstones: examples from the Mid-Proterozoic Belt Supergroup, Montana, U.S.A. Sedimentary Geology 120: 105–124.Google Scholar
Schieber, J. 2002. The role of an organic slime matrix in the formation of pyritized burrow trails and pyrite concretions. Palaios 17: 104–109.Google Scholar
Schneider, D. A., Bickford, M. E., Cannon, W. F., Schulz, K. J., and Hamilton, M. A. 2002. Age of volcanic rocks and syndepositional iron formations, Marquette Range Supergroup: implications for the tectonic setting of Paleoproterozoic iron formations of the Lake Superior region. Canadian Journal of Earth Sciences 39: 999–1012.Google Scholar
Schweitzer, C. E., Feldmann, R. M., Marenssi, S., and Waugh, D. A. 2005. Remarkably preserved annelid worms from the La Meseta Formation (Eocene), Seymour Island, Antarctica. Palaeontology 48: 1–13.Google Scholar
Seilacher, A., Bose, P. K., and Pflüger, F. 1998. Triploblastic animals more than 1 billion years ago: trace fossil evidence from India. Science 282: 80–83.Google Scholar
Seilacher, A., Grazhdankin, D., and Legouta, A. 2003. Ediacaran biota: the dawn of animal life in the shadow of giant protists. Paleontological Research 7: 43–54.Google Scholar
Shapiro, J. A. and Dworkin, M. eds. 1997. Bacteria as multicellular organisms. Oxford University Press, Oxford.Google Scholar
Shen, Y., Knoll, A. H., and Walter, M. R. 2003. Evidence for low sulphate and anoxia in a mid-Proterozoic marine basin. Nature 423: 632–635.Google Scholar
Shimkets, L. J. 1990. Social and developmental biology of myxobacteria. Microbiological Reviews 54: 473–501.Google Scholar
Song, Y., Black, R. G., and Lipps, J. H. 1994. Morphological optimization in the largest living foraminifera: implications from finite element analysis. Paleobiology 20: 14–26.Google Scholar
Sun, W. 1986. Precambrian medusoids: the plexus and -like pseudofossils. Precambrian Research 31: 325–360.Google Scholar
Sun, W., Wang, G., and Zhou, B. 1986. Macroscopic worm-like body fossils from the Upper Precambrian (900-700 Ma), Huainan District, Anhui, China and their stratigraphic and evolutionary significance. Precambrian Research 31: 377–403.Google Scholar
Tendal, O. S. 1972. A monograph of the Xenophyophoria. Galathea Report 12: 1–103.Google Scholar
Thomsen, E. and Vorren, T. O. 1984. Pyritization of tubes and burrows from Late Pleistocene continental shelf sediments off north Norway. Sedimentology 31: 481–492.Google Scholar
Turek, A. and Stephenson, N. C N. 1966. The radiometric age of the Albany granite and the Stirling Range Beds, southwest Australia. Journal of the Geological Society of Australia 13: 449–456.Google Scholar
Walter, M. R. 1994. Stromatolites: the main geological source of information on the evolution of the early benthos. pp. 270–286in Bengtson, S., ed. Early life on Earth. Columbia University Press, New York.Google Scholar
Wang, D. Y C., Kumar, S., and Hedges, S. B. 1999. Divergence time estimates for the early history of animal phyla and the origin of plants, animals and fungi. Proceedings of the Royal Society of London B 266: 163–171.Google Scholar
Wang, G. X. 1982. Late Precambrian Annelida and Pogonophora from the Huainan of Anhui Province. Tianjin Institute of Geology and Mineral Resources Bulletin 1982 6: 9–22.Google Scholar
Westblad, E. 1950. n.g., n.sp., a peculiar, primitive Turbellarian type. Arkiv för Zoologi 1 3: 11–29.Google Scholar
Wilkins, M. R. and Williams, K. L. 1995. The extracellular matrix of the slug. Experientia Basel 51: 1189–1196.Google Scholar
Woolnough, W. G. 1920. A geological reconnaissance of the Stirling Ranges of Western Australia. Journal and Proceedings of the Royal Society of New South Wales 54: 79–112.Google Scholar
Wray, G. A., Levinton, J. S., and Shapiro, L. H. 1996. Molecular evidence for deep pre-Cambrian divergences among metazoan phyla. Science 274: 568–573.Google Scholar
Zhang, Z. 1988. Du emend.: an earliest record of bryophyte-like fossils. Acta Palaeontologica Sinica 27: 416–426. [In Chinese with English abstract.].Google Scholar
Zhu, S. and Chen, H. 1995. Megascopic multicellular organisms from the 1700-million-year-old Tuanshanzi Formation in the Jixian area, North China. Science 270: 620–622.Google Scholar
Zhu, S., Sun, S., Huang, X., He, Y., Zhu, G., Sun, L., and Zhang, K. 2000. Discovery of carbonaceous compressions and their multicellular tissues from the Changzhougou Formation (1800 Ma) in the Yanshan Range, North China. Chinese Science Bulletin 45: 841–847.Google Scholar