The Cambrian Explosion

Visual sources include third-party material incorporated into custom animations. License information is reproduced from source records; an unrecorded license does not mean a work is public domain.

• Fortune Head GSSP, Newfoundland

  Liam Herringshaw

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• T pedum at base of Cambrian

  Martin Smith

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• Small shelly fossils from the Yangjiagou Member, Lowermost Cambrian of Tongying Formation, southern Shaanxi, Northwestern China

  Luo, M., Brock, G.A., Liang, Y., Song, B., Hu, Y., Liu, F. & Zhang, Z.

  View original source ↗CC BY-SA 4.0

• Early Cambrian shelly fossils from Siberia, Zhuravlev and Wood 2018 figure 2

  Photographs: Artem Kouchinsky; figure: Andrey Yu Zhuravlev and Rachel A Wood

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  Incorporated into an explanatory animation; presentation may include cropping, labels and overlays.

• MICRODICTYON SINICUM

  Masahiro miyasaka

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• Microdictyon sinicum from the early Cambrian Chengjiang Lagerstätte

  Chen, A., Vannier, J., Guo, J., Wang, D., Gąsiorek, P., Han, J., Ma, W.

  View original source ↗CC BY 4.0

• Eoredlichia intermedia, Chengjiang biota 3

  Woudloper

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• Fuxianhuia protensa (YPM IP 421686)

  Jessica Utrup

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  Incorporated into an explanatory animation; presentation may include cropping, labels and overlays.

• Maotianshan shale outcrop

  Martin Smith

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• Eye of the dragonfly (7346824986)

  photochem_PA from State College, PA, USA

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• Carcinus maenas

  Hans Hillewaert

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• Araneus diadematus - Keila

  Ivar Leidus

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• Ciempiés (Lithobius forficatus), Hartelholz, Múnich, Alemania, 2020-06-28, DD 679-724 FS

  Diego Delso

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• Isoxys Chengjiang CRF

  Dwergenpaartje

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• Isoxys curvirostratus fossil and CT anatomy, Zhang et al. 2023 figure 1

  Caixia Zhang, Yu Liu, Javier Ortega-Hernandez, Joanna M. Wolfe, Changfei Jin, Huijuan Mai, Xianguang Hou, Jin Guo and Dayou Zhai

  View original source ↗CC BY 4.0

• Isoxys anatomical reconstruction, Zhang et al. 2023 figure 3

  Caixia Zhang et al.

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• Innovatiocaris maotianshanensis ELRC 20001

  Gaëtan J.-M. Potin and Allison C. Daley

  View original source ↗CC BY 4.0

• Functional head region of Amplectobelua symbrachiata

  Peiyun Cong, Allison C. Daley, Gregory D. Edgecombe & Xianguang Hou

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  Incorporated into an explanatory animation; presentation may include cropping, labels and overlays.

• 耳材村海口鱼 Haikouichthys ercaicunensis-早寒武世 EarlyCambrian-澄江生物群 Chengjiang Biota-澄江化石地世界自然遗产博物馆 2025-08-09

  Kcx36

  View original source ↗CC BY-SA 4.0

• Myllokunmingia fengjiaoa RCCBYU-10200a

  Farid Saleh​, Xiaoya Ma​, Pauline Guenser, M. Gabriela Mángano, Luis A. Buatois, Jonathan B. Antcliffe

  View original source ↗CC BY 4.0

• WalcottQuarry080509

  Mark A. Wilson ( Wilson44691 ) (Department of Geology, The College of Wooster). [1]

  View original source ↗Public domain

• Field notebook of Charles D. Walcott from August 31 to September 3, 1909

  Charles D. Walcott (photo by Brian Boyle)

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• USNM PAL 57674 Marrella splendens Image 01

  Jean-Bernard Caron

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  Incorporated into an explanatory animation; presentation may include cropping, labels and overlays.

• Charles Walcott, Sidney and Helen at Burgess Shale quarry, 1913

  Smithsonian Institution Archives; photographer not identified

  View original source ↗Copyrighted material — used for documentary commentary

  Editorial use; no open license asserted.

• USNM PAL 57683 Opabinia regalis Image 3

  Han Zeng

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• 20191108 Opabinia regalis

  Junnn11

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• USNM PAL 83935 Hallucigenia sparsa Image 1

  Han Zeng

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• Living velvet worm on forest substrate

  Keith

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  Incorporated into an explanatory animation; presentation may include cropping, labels and overlays.

• Wiwaxia 3G crop

  Martin R. Smith

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• USNM PAL 57628 Pikaia gracilens

  Chip Clark

  View original source ↗CC0

• Schematic anatomical reconstruction of Pikaia flipped

  Giovanni Mussini, M. Paul Smith, Jakob Vinther, Imran A. Rahman, Duncan J.E. Murdock, David A.T. Harper, Frances S. Dunn

  View original source ↗CC BY 4.0

• Vauxia gracilenta 343

  Ghedoghedo

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• USNM PAL 58588b Olenoides serratus Image 7

  Han Zeng

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• Scientific figure · source page 11

  Jean Vannier

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  Figure or page excerpt cropped from the source publication.

• USNM PAL 57703 Canadaspis perfecta Image 03

  Jean-Bernard Caron

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• Anomalocaris canadensis (TMP 2023.003.0003), Royal Tyrrell Museum, Drumheller, Alberta, 2025-07-13

  Chris Woodrich

  View original source ↗CC BY-SA 4.0

• Aria et al. 2020 Anomalocaris canadensis head ROMIP 51212

  Cédric Aria, Fangchen Zhao, Han Zeng, Jin Guo & Maoyan Zhu

  View original source ↗CC BY 4.0

• Rspb20230638f03

  Russell D. C. Bicknell, Michel Schmidt, Imran A. Rahman, Gregory D. Edgecombe, Susana Gutarra, Allison C. Daley, Roland R. Melzer, Stephen Wroe and John R. Paterson

  View original source ↗CC BY 4.0

• Rspb20230638f04

  Russell D. C. Bicknell, Michel Schmidt, Imran A. Rahman, Gregory D. Edgecombe, Susana Gutarra, Allison C. Daley, Roland R. Melzer, Stephen Wroe and John R. Paterson

  View original source ↗CC BY 4.0

• Anomalocaris and Echidnacaris eyes

  Gaëtan J.-M. Potin and Allison C. Daley

  View original source ↗CC BY 4.0

• Elrathia kingii fossil trilobite with healed bite mark (Wheeler Formation, Middle Cambrian; House Range, western Utah, USA) 2 (15252026101)

  James St. John

  View original source ↗CC BY 2.0

• Sidneyia gut contents, Zacai et al. 2016 figure 9

  Axelle Zacaï, Jean Vannier and Rudy Lerosey-Aubril

  View original source ↗Copyrighted material — used for documentary commentary

  Incorporated into an explanatory animation; presentation may include cropping, labels and overlays.

  Editorial use; no open license asserted.

• Lapworthella thickness and perforation record, Bicknell et al. 2025 figure 2

  Russell D. C. Bicknell, Nicolas E. Campione, Glenn A. Brock and John R. Paterson

  View original source ↗Copyrighted material — used for documentary commentary

  Editorial use; no open license asserted.

• Perforated Lapworthella sclerites, Bicknell et al. 2025 figure 1

  Russell D. C. Bicknell, Nicolas E. Campione, Glenn A. Brock and John R. Paterson

  View original source ↗Copyrighted material — used for documentary commentary

  Editorial use; no open license asserted.

• Audio mixer close up

  Lchader

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  Incorporated into an explanatory animation; presentation may include cropping, labels and overlays.

• Camarón mantis (Odontodactylus scyllarus), Anilao, Filipinas, 2023-08-24, DD 164

  Diego Delso

  View original source ↗CC BY-SA 4.0

  Incorporated into an explanatory animation; presentation may include cropping, labels and overlays.

Research references

Selected sources from the episode’s research and scientific figures.

1. DOI: 10.1126/science.1206375 ↗
2. DOI: 10.1038/s41559-019-0821-6 ↗
3. DOI 10.1111/ter.12368 ↗
4. DOI: 10.1130/G31036.1 ↗
5. DOI: 10.1038/s41467-022-29246-z ↗
6. DOI: 10.1038/46965 ↗
7. DOI: 10.1016/j.cub.2024.05.026 ↗
8. DOI: 10.1038/nature14573 ↗
9. DOI: 10.1186/s13227-024-00222-6 ↗
10. DOI: 10.1098/rspb.2023.0638 ↗
11. DOI: 10.1038/nature10689 ↗
12. DOI: 10.1126/sciadv.abc6721 ↗
13. article ↗
14. DOI: 10.1038/41786 ↗
15. DOI: 10.1126/science.1085672 ↗
16. PMC ↗
17. DOI: 10.1016/j.chemgeo.2025.122890 ↗
18. DOI: 10.1126/sciadv.ads2846 ↗
19. DOI: 10.1038/s41586-026-10590-9 ↗
20. DOI: 10.1038/s41586-025-10030-0 ↗
21. linnemann 2019 boundary ↗
22. GSSP slab photograph ↗
23. Yangjiagou assemblage plate ↗
24. *Haikouichthys* museum specimen ↗
25. *Fuxianhuia protensa* specimen ↗
26. Royal Tyrrell display specimen ↗
27. *Anomalocaris* and *Echidnacaris* eyes ↗
28. USNM PAL 57683 ↗
29. USNM PAL 83935 ↗
30. USNM PAL 57674 ↗
31. *Wiwaxia* specimen crop ↗
32. USNM PAL 57628 ↗
33. 2024 flipped schematic ↗
34. 31 Aug.–3 Sep. 1909 field notebook ↗
35. Cambrian *Elrathia* injury ↗
36. https://commons.wikimedia.org/wiki/File:Fuxianhuia_protensa_(YPM_IP_421686).jpg ↗
37. https://commons.wikimedia.org/wiki/File:Anomalocaris_canadensis_(TMP_2023.003.0003),_Royal_Tyrrell_Museum,_Drumheller,_Alberta,_2025-07-13.jpg ↗
38. https://commons.wikimedia.org/wiki/File:Field_notebook_of_Charles_D._Walcott_from_August_31_to_September_3,_1909.jpg): ↗
39. https://commons.wikimedia.org/wiki/File:Elrathia_kingii_fossil_trilobite_with_healed_bite_mark_(Wheeler_Formation,_Middle_Cambrian;_House_Range,_western_Utah,_USA)_2_(15252026101).jpg): ↗
40. ics chart 2026 06 ↗
41. DOI: 10.1017/S0016756811000720 ↗
42. DOI: 10.1144/jgs2017-103 ↗
43. DOI 10.1144/jgs2015-083 ↗
44. PMC ↗
45. How old is the Burgess Shale? ↗
46. DOI: 10.1017/pab.2019.42 ↗
47. Fortunian GSSP ↗
48. Fortune Head paper ↗
49. HAL record ↗
50. DOI: 10.1111/gbi.12550 ↗
51. DOI: 10.1111/brv.12614 ↗
52. *Treptichnus pedum* diagram ↗
53. 3-D diagram ↗
54. Tanafjord *T. pedum* specimen ↗
55. PMC ↗
56. Scandinavian University Press ↗
57. https://commons.wikimedia.org/wiki/File:Treptichnus_pedum_from_the_Fortunian_(lowermost_Cambrian)of_Tanafjord,_Norway.png ↗
58. Nature Communications ↗
59. Chengjiang Fossil Site ↗
60. BioOne ↗
61. Nature Communications article ↗
62. PMC ↗
63. DOI: 10.1111/j.1502-3931.2010.00239.x ↗
64. BMC Evolutionary Biology ↗
65. National Science Review ↗
66. paper record ↗
67. Commons ↗
68. book source ↗
69. PNAS/PMC ↗
70. DOI: 10.1038/nature01264 ↗
71. DOI: 10.1038/s41586-025-09966-0 ↗
72. Science ↗
73. DOI: 10.1126/science.ade9707 ↗
74. museum specimen ↗
75. *Eoredlichia intermedia* ↗
76. *Microdictyon sinicum* specimen ↗
77. open paper figure ↗
78. The Walcott Quarry community ↗
79. ROM *Marrella splendens* ↗
80. ROM *Opabinia regalis* ↗
81. DOI: 10.1111/j.1502-3931.2011.00264.x ↗
82. Nature ↗
83. ROM species page ↗
84. ROM *Wiwaxia corrugata* ↗
85. Proceedings B ↗
86. ROM *Anomalocaris canadensis* ↗
87. PMC ↗
88. ROM *Hurdia victoria* ↗
89. PMC ↗
90. ROM species page ↗
91. DOI: 10.1098/rsos.242122 ↗
92. ROM *Olenoides serratus* ↗
93. ROM *Canadaspis perfecta* ↗
94. ROM *Sidneyia inexpectans* ↗
95. ROM *Burgessochaeta setigera* ↗
96. ROM *Ottoia prolifica* ↗
97. ROM *Pikaia gracilens* ↗
98. field notes ↗
99. discovery record ↗
100. Burgess Shale collection ↗
101. ROM Burgess Shale projects ↗
102. ROMIP 51214 ↗
103. open head figure ↗
104. Smithsonian object record ↗
105. Burgess Shale fossils ↗
106. BioOne ↗
107. DOI: 10.1007/s00114-012-0910-8 ↗
108. DOI: 10.1080/14772019.2023.2225066 ↗
109. Fossilised *Anomalocaris*-type eye ↗
110. *Echidnacaris* eye ↗
111. PMC context ↗
112. PLOS ONE ↗
113. https://commons.wikimedia.org/wiki/File:Elrathia_kingii_fossil_trilobite_with_healed_bite_mark_(Wheeler_Formation,_Middle_Cambrian;_House_Range,_western_Utah,_USA)_2_(15252026101).jpg ↗
114. DOI: 10.1111/j.1469-185X.1999.tb00046.x ↗
115. ROM stem/crown explanation ↗
116. PMC ↗
117. Nature ↗
118. Current Biology ↗
119. https://www.cell.com/current-biology/fulltext/S0960-9822(24)00669-9 ↗
120. FBgg0000363 ↗
121. PMC ↗
122. Hox genes in *Drosophila* ↗
123. Open Drosophila CNS Hox expression figure ↗
124. MBL Drosophila embryo Hox panels ↗
125. MDPI mouse/Hox schematic ↗
126. Open vertebrate Hox figure ↗
127. University of Utah Hox explainer ↗
128. Development ↗
129. Development ↗
130. Hox genes ↗
131. DOI: 10.1073/pnas.1312778110 ↗
132. open text ↗
133. DOI: 10.1111/pala.12732 ↗
134. open text ↗
135. Fortune Head GSSP ↗

Music

• Meditation From The Star Orion
  OctahedronMusic · Envato Elements