The document discusses windows into early marine ecosystems from 600 million years ago preserved in formations like the Doushantuo in South China. It summarizes evidence from different preservation environments (windows) that indicates the earliest animals and algae lived during this period before the Cambrian explosion, including microscopic fossils of possible embryos, algae, and animals with unusual body plans preserved in chert, shale, and phosphorite. These windows provide a glimpse of the diversity of life that may have ignited the Cambrian explosion over 50 million years later.

1. Windows into the Marine Ecosystems of
600 Million Years Ago
Shuhai Xiao
Department of Geosciences
Virginia Polytechnic Institute and State University, Blacksburg, VA 24061
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2. Tiksi, Arctic Siberia
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3. 3

4. The best mosquitoes are dead mosquitoes
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5. Namibia
(Dunn et al., 2008)

6. South China
(Dunn et al., 2008)

7. The Cambrian Explosion
Consequently, if my theory be
true, it is indisputable that
before the lowest Cambrian
stratum was deposited, the
world swarmed with living
creatures .
I look at the natural geological
record, as a history of the world
imperfectly kept only here
and there a short chapter has
been preserved
(Darwin, 1859)

8. Billion years (Ga = 1000 Ma)
Phanerozoic
0.5
Cambrian
Ediacaran
Cryogenian Neoproterozoic
Neoproterozoic
Tonian
1.0
Mesoproterozoic
Proterozoic
1.6
Paleoproterozoic
2.5
Archean
4.0
Hadean
8
4.5

9. Doushantuo Formation: Localities and Windows
Yangtze Gorges
(C, Si)
Weng an (P)
(Zhu, 2004)
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10. Lower Doushantuo Chert Window
Subtidal, early diagenetic chert nodules are abundant in Doushantuo Fm;
Three dimensional preservation of microfossils in nodules;
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11. Chert window: Acanthomorphic (spiny) acritarchs
100 mm 50 mm
50 mm 50 mm
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12. What are Ediacaran Acanthomorphs?
(Yin et al., 2007)
Some Ediacaran acanthomorphs may represent animal embryos;
They extend to the base of the Doushantuo Formation, ~632 Ma;
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13. Doushantuo Shale Window
551 Ma ash
Carbonaceous compression fossils in uppermost Doushantuo

14. Shale window: Seaweeds or Algae
0.5 cm
1 cm
Millimetric to decimetric;
Holdfast; Dichotomous branching;
Apical meristematic growth;
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15. Shale window: Seaweeds & Animals
Scales: 5 mm
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16. Shale window: Animals?
Doushantuo annulated tubes; some were interpreted as animals;
Holdfast, -- benthic; Possibly siphonous, coenocytic algae;
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17. Shale window: Animals?
1 cm 1 cm
Doushantuo tubular fossil: Calyptrina striata Modern pogonophoran tubes
Large flanged tubes;
Cnidarian or pogonophoran tubes?

18. Shale Window: Eight-armed animals?
(Tang et al., 2008; Zhu et al., 2008)
Eoandromeda: Each consists of eight clockwise spiral arms;
Similar fossils from South Australia;
Early animals? 18

19. Upper Doushantuo Phosphorite Window
40 m thick;
Two phosphorite horizons separated by dolostone and karstification surface;
Fossils in upper phosphorite; 19

20. Acanthomorphs in different taphonomic windows
100 mm 100 mm 50 mm
phosphatization silicification carbonaceous compression
Similar acanthomorphs are found in Australia, South China, northern
India, Svalbard, southern Norway, Siberia, East European Platform;
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21. Phosphorite window: Algae
50 mm
Phosphatized Silicified
Cellularly preserved multicellular algae;
Found in both chert and phosphorite windows;
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22. Phosphorite window: Algae
20 mm
Cell division events were preserved, indicating rigid cell wall;
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23. Phosphorite window: Algae
Cellular, tissue, and reproductive differentiation (e.g.,
conceptacles);
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24. Phosphorite window: Animal Embryos
(Hagadorn et al., 2006)
Animal stereoblastulae from the Doushantuo Formation;
Cellular and sub-cellular preservation; 24

25. 25

26. Phosphorite window: Sub-cellular Structures
500 mm
Comparison between vesicles in fossil embryo and modern sponge embryo (lower right)
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27. Phosphorite window: Animal Embryos
Embryo ~600 mm in diameter
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28. Phosphorite window: Spiral Embryos?
(Courtesy of Phil Donoghue)
Three clockwise coils, with no exception;
Earliest known evidence for biological chirality;
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29. Modern and Fossil Resting Eggs
200 mm
Modern Modern
Fossil Fossil
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30. White Sea, Russia: Yorgia
(Ivantsov and Malakhovskaya, 2002; Fedonkin, 2003)
Passive intermittent movement;
Alternate bilateral symmetry;
Bilaterally symmetric animals? 30

31. White Sea, Russia: Kimberella
(Fedonkin, 2003; Ivantsov, 2009)
Dorsal-ventral and anterior-posterior differentiation;
Grazing activities and active self-powered locomotion;
Likely bilaterian animals; 31

32. Animal Burrows
1 cm
The presence of Ediacaran bilaterian animals is also
supported by trace fossils;
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33. Nama Group, Namibia:
Animal Biomineralization and Predation
0.5 mm
(Bengtson and Yue, 1992; Hua et al., 2003)
Cloudina, the earliest biomineralizing animals;
Drill holes suggest inter-species ecological interactions;
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34. Conclusions
Multiple windows (or volumes in different
dialects ): Ediacaran Period represents a
fuse to the Cambrian explosion;
But what ignited the fuse?
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35. Acknowledgments
NSF Sedimentary Geology & Paleobiology;
Virginia Tech X-ray CT laboratory;
Phil Donoghue, Jim Schiffbauer, Xunlai
Yuan, Chuanming Zhou;
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36. An Ediacaran Fuse of the Cambrian Explosion?
Cambrian
545 Ma Nama assemblage
555 Ma White Sea assemblage
Ediacaran Period
565 Ma
Avalon assemblage
575 Ma
585 Ma Doushantuo biota
595 Ma
605 Ma
615 Ma
625 Ma
635 Ma
Cryogenian Marinoan snowball
Doushantuo (635-551 Ma), Avalon (575-560 Ma), White Sea
(560-550 Ma), Nama (550-541 Ma);
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37. Temporal Distribution of Avalon-White Sea-Nama Fossils
(Xiao and Laflamme, 2009)
Many have unusual bodyplans (triradial, tetraradial, pentaradial, octaradial);
Diploblastic grade animals with a greater diversity of bodyplans in Ediacaran?
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38. 100 mm Phosphorite window: Adult animals?
Tubular fossils with perforated crosswalls: possible stem group cnidarians?
Ontogenetically related to the spheroidal microfossils?
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39. Phosphorite window: Embryonic development?
Blastulas
Spiral embryos 100 mm
Are blastula stages and spiral fossils ontogenetically or
phylogenetically related? 39

40. Phosphorite window: Algae
50 mm
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41. Phosphorite window: Animal Embryos
(Hagadorn et al., 2006)
(Xiao et al., 2007)
Animal stereoblastulae from the Doushantuo Formation;
Cellular and sub-cellular preservation; 41