Windows into the Marine Ecosystems of       600 Million Years Ago                           Shuhai Xiao                   ...
Tiksi, Arctic Siberia                        2
3
The best mosquitoes are dead mosquitoes                                          4
Namibia(Dunn et al., 2008)
South China(Dunn et al., 2008)
The Cambrian Explosion           Consequently, if my theory be          true, it is indisputable that          before the ...
Billion years (Ga = 1000 Ma)Phanerozoic                          0.5                             Cambrian                 ...
Doushantuo Formation: Localities and Windows                                 Yangtze Gorges                               ...
Lower Doushantuo Chert WindowSubtidal, early diagenetic chert nodules are abundant in Doushantuo Fm;Three dimensional pres...
Chert window: Acanthomorphic (spiny) acritarchs      100 mm             50 mm       50 mm                     50 mm       ...
What are Ediacaran Acanthomorphs?                          (Yin et al., 2007)Some Ediacaran acanthomorphs may represent an...
Doushantuo Shale Window                                    551 Ma ashCarbonaceous compression fossils in uppermost Doushan...
Shale window: Seaweeds or Algae                       0.5 cm         1 cm    Millimetric to decimetric;    Holdfast; Dicho...
Shale window: Seaweeds & Animals                            Scales: 5 mm                                           15
Shale window: Animals?Doushantuo annulated tubes; some were interpreted as animals;Holdfast, -- benthic; Possibly siphonou...
Shale window: Animals?       1 cm                     1 cmDoushantuo tubular fossil: Calyptrina striata   Modern pogonopho...
Shale Window: Eight-armed animals?(Tang et al., 2008; Zhu et al., 2008)  Eoandromeda: Each consists of eight clockwise spi...
Upper Doushantuo Phosphorite Window 40 m thick; Two phosphorite horizons separated by dolostone and karstification surface...
Acanthomorphs in different taphonomic windows100 mm                     100 mm                       50 mm         phospha...
Phosphorite window: Algae                                                        50 mm            Phosphatized            ...
Phosphorite window: Algae                   20 mmCell division events were preserved, indicating rigid cell wall;         ...
Phosphorite window: AlgaeCellular, tissue, and reproductive differentiation (e.g.,conceptacles);                          ...
Phosphorite window: Animal Embryos                                     (Hagadorn et al., 2006)Animal stereoblastulae from ...
25
Phosphorite window: Sub-cellular Structures           500 mmComparison between vesicles in fossil embryo and modern sponge...
Phosphorite window: Animal Embryos          Embryo ~600 mm in diameter                                       27
Phosphorite window: Spiral Embryos?                                           (Courtesy of Phil Donoghue)Three clockwise c...
Modern and Fossil Resting Eggs                200 mmModern                     ModernFossil                     Fossil    ...
White Sea, Russia: Yorgia    (Ivantsov and Malakhovskaya, 2002; Fedonkin, 2003)Passive intermittent movement;Alternate bil...
White Sea, Russia: Kimberella                                        (Fedonkin, 2003; Ivantsov, 2009)Dorsal-ventral and an...
Animal Burrows      1 cmThe presence of Ediacaran bilaterian animals is alsosupported by trace fossils;                   ...
Nama Group, Namibia:    Animal Biomineralization and Predation              0.5 mm                         (Bengtson and Y...
ConclusionsMultiple windows (or volumes in differentdialects ): Ediacaran Period represents afuse to the Cambrian explosio...
AcknowledgmentsNSF Sedimentary Geology & Paleobiology;Virginia Tech X-ray CT laboratory;Phil Donoghue, Jim Schiffbauer, Xu...
An Ediacaran Fuse of the Cambrian Explosion?         Cambrian545 Ma                                    Nama assemblage555 ...
Temporal Distribution of Avalon-White Sea-Nama Fossils                                                        (Xiao and La...
100 mm   Phosphorite window: Adult animals?  Tubular fossils with perforated crosswalls: possible stem group cnidarians?  ...
Phosphorite window: Embryonic development?                           Blastulas                              Spiral embryos...
Phosphorite window: Algae                 50 mm                            40
Phosphorite window: Animal Embryos                                     (Hagadorn et al., 2006)    (Xiao et al., 2007)Anima...
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Xiao April Cafe 2011

  1. 1. Windows into the Marine Ecosystems of 600 Million Years Ago Shuhai Xiao Department of GeosciencesVirginia Polytechnic Institute and State University, Blacksburg, VA 24061 1
  2. 2. Tiksi, Arctic Siberia 2
  3. 3. 3
  4. 4. The best mosquitoes are dead mosquitoes 4
  5. 5. Namibia(Dunn et al., 2008)
  6. 6. South China(Dunn et al., 2008)
  7. 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. 8. Billion years (Ga = 1000 Ma)Phanerozoic 0.5 Cambrian Ediacaran Cryogenian NeoproterozoicNeoproterozoic Tonian 1.0MesoproterozoicProterozoic 1.6Paleoproterozoic 2.5Archean 4.0Hadean 8 4.5
  9. 9. Doushantuo Formation: Localities and Windows Yangtze Gorges (C, Si) Weng an (P) (Zhu, 2004) 9
  10. 10. Lower Doushantuo Chert WindowSubtidal, early diagenetic chert nodules are abundant in Doushantuo Fm;Three dimensional preservation of microfossils in nodules; 10
  11. 11. Chert window: Acanthomorphic (spiny) acritarchs 100 mm 50 mm 50 mm 50 mm 11
  12. 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; 12
  13. 13. Doushantuo Shale Window 551 Ma ashCarbonaceous compression fossils in uppermost Doushantuo
  14. 14. Shale window: Seaweeds or Algae 0.5 cm 1 cm Millimetric to decimetric; Holdfast; Dichotomous branching; Apical meristematic growth; 14
  15. 15. Shale window: Seaweeds & Animals Scales: 5 mm 15
  16. 16. Shale window: Animals?Doushantuo annulated tubes; some were interpreted as animals;Holdfast, -- benthic; Possibly siphonous, coenocytic algae; 16
  17. 17. Shale window: Animals? 1 cm 1 cmDoushantuo tubular fossil: Calyptrina striata Modern pogonophoran tubes Large flanged tubes; Cnidarian or pogonophoran tubes?
  18. 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. 19. Upper Doushantuo Phosphorite Window 40 m thick; Two phosphorite horizons separated by dolostone and karstification surface; Fossils in upper phosphorite; 19
  20. 20. Acanthomorphs in different taphonomic windows100 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; 20
  21. 21. Phosphorite window: Algae 50 mm Phosphatized SilicifiedCellularly preserved multicellular algae;Found in both chert and phosphorite windows; 21
  22. 22. Phosphorite window: Algae 20 mmCell division events were preserved, indicating rigid cell wall; 22
  23. 23. Phosphorite window: AlgaeCellular, tissue, and reproductive differentiation (e.g.,conceptacles); 23
  24. 24. Phosphorite window: Animal Embryos (Hagadorn et al., 2006)Animal stereoblastulae from the Doushantuo Formation;Cellular and sub-cellular preservation; 24
  25. 25. 25
  26. 26. Phosphorite window: Sub-cellular Structures 500 mmComparison between vesicles in fossil embryo and modern sponge embryo (lower right) 26
  27. 27. Phosphorite window: Animal Embryos Embryo ~600 mm in diameter 27
  28. 28. Phosphorite window: Spiral Embryos? (Courtesy of Phil Donoghue)Three clockwise coils, with no exception;Earliest known evidence for biological chirality; 28
  29. 29. Modern and Fossil Resting Eggs 200 mmModern ModernFossil Fossil 29
  30. 30. White Sea, Russia: Yorgia (Ivantsov and Malakhovskaya, 2002; Fedonkin, 2003)Passive intermittent movement;Alternate bilateral symmetry;Bilaterally symmetric animals? 30
  31. 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. 32. Animal Burrows 1 cmThe presence of Ediacaran bilaterian animals is alsosupported by trace fossils; 32
  33. 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; 33
  34. 34. ConclusionsMultiple windows (or volumes in differentdialects ): Ediacaran Period represents afuse to the Cambrian explosion;But what ignited the fuse? 34
  35. 35. AcknowledgmentsNSF Sedimentary Geology & Paleobiology;Virginia Tech X-ray CT laboratory;Phil Donoghue, Jim Schiffbauer, XunlaiYuan, Chuanming Zhou; 35
  36. 36. An Ediacaran Fuse of the Cambrian Explosion? Cambrian545 Ma Nama assemblage555 Ma White Sea assemblage Ediacaran Period565 Ma Avalon assemblage575 Ma585 Ma Doushantuo biota595 Ma605 Ma615 Ma625 Ma635 Ma Cryogenian Marinoan snowball Doushantuo (635-551 Ma), Avalon (575-560 Ma), White Sea (560-550 Ma), Nama (550-541 Ma); 36
  37. 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? 37
  38. 38. 100 mm Phosphorite window: Adult animals? Tubular fossils with perforated crosswalls: possible stem group cnidarians? Ontogenetically related to the spheroidal microfossils? 38
  39. 39. Phosphorite window: Embryonic development? Blastulas Spiral embryos 100 mm Are blastula stages and spiral fossils ontogenetically or phylogenetically related? 39
  40. 40. Phosphorite window: Algae 50 mm 40
  41. 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
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