What was the "Cambrian Explosion" ?

Cambrian explosion or Cambrian radiation. (Adobe Stock) FILE #: 46230229

Photo credit: canbedone (Adobe Stock)

The Cambrian Explosion

Cambrian radiation or early Cambrian diversification refers to an interval of time approximately 541 million years ago in the Cambrian Period when practically all major animal phyla started appearing in the fossil record. It lasted for about 13 – 25 million years and resulted in the divergence of most modern metazoan phyla. The event was accompanied by major diversification in other groups of organisms as well.

Before early Cambrian diversification, most organisms were relatively simple, composed of individual cells, or small multicellular organisms, occasionally organized into colonies. As the rate of diversification subsequently accelerated, the variety of life became much more complex, and began to resemble that of today. Almost all present-day animal phyla appeared during this period.

Some recent advances suggest that there is no clearly definable "Cambrian Explosion" event in the fossil record, but rather that there was a progression of transitional radiations starting with the Ediacaran period and continuing at a similar rate into the Cambrian.

Let's look at some of the awesome Prehistoric Creatures from the Cambrian Era!

The Cambrian Explosion by Masato Hattori. (http://masahatto2.p2.bindsite.jp/index.html)

Photo credit: Masahatto Hattori

Trilobites

Joachim Barrande (1799-1883) - http://www.granit-publishing.cz/?l=en&e=18&k=47&m=

Plate 3 from "Système silurien du centre de la Bohême" Vol I Supplement II

Trilobite Fossils

Photo by Wes Warren on Unsplash

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Trilobites ( /ˈtraɪləˌbaɪt, ˈtrɪ-, -loʊ-/; meaning "three lobes") are a group of extinct marine arthropods that form the class Trilobita. Trilobites form one of the earliest-known groups of arthropods.

The first appearance of trilobites in the fossil record defines the base of the Atdabanian stage of the Early Cambrian period (521 million years ago), and they flourished throughout the lower Paleozoic before slipping into a long decline, when, during the Devonian, all trilobite orders except the Proetida died out. The last extant trilobites finally disappeared in the mass extinction at the end of the Permian about 252 million years ago. Trilobites were among the most successful of all early animals, existing in oceans for almost 270 million years, with over 20,000 species having been described.

Anomalocaris

Anomalocaris by Masato Hattori. (http://masahatto2.p2.bindsite.jp/index.html)

Photo credit: Masahatto Hattori

Gif image source: https://walkingwith.fandom.com/wiki/Anomalocaris

© Walking with monsters. 2005

The interpretation of Anomalocaris as an active predator is widely accepted throughout the history of research, as its raptorial frontal appendages and mid-gut glands strongly suggest a predatory lifestyle.

In the case of A. canadensis, its outstanding size amongst Burgess Shale fauna also making it one of the first apex predators known to exist.

Cambrian period, underwater scene with Anomalocaris, Opabinia, Hallucigenia, Pirania and Dinomischus (3d science illustration) 

Photo credit: Dotted Yeti

Radiodonta group of Arthropods

Radiodonta is an extinct order of stem-group arthropods that was successful worldwide during the Cambrian period. 

Left to right, top to bottom: Amplectobelua symbrachiata, Anomalocaris canadensis, Aegirocassis benmoulai, Peytoia nathorsti, Lyrarapax unguispinus, Cambroraster falcatus, and Hurdia victoria.

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File:20191201 Radiodonta Amplectobelua Anomalocaris Aegirocassis Lyrarapax Peytoia Laggania Hurdia.png

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What life forms emerged next?

The Ordovician Period by Masato Hattori. (http://masahatto2.p2.bindsite.jp/index.html)

Photo credit: Masahatto Hattori

The Ordovician spans 41.6 million years from the end of the Cambrian Period 485.4 million years ago to the start of the Silurian Period 443.8 Milliom years ago.

References, bibliography & further reading:

Photo credits: http://masahatto2.p2.bindsite.jp/index.html

Zhuravlev, Andrey; Riding, Robert (2000). The Ecology of the Cambrian Radiation. Columbia University Press. ISBN 978-0-231-10613-9. The Cambrian radiation was the explosive evolution of marine life that started 550,000,000 years ago. It ranks as one of the most important episodes in Earth history. This key event in the history of life on our planet changed the marine biosphere and its sedimentary environment forever, requiring a complex interplay of wide-ranging biologic and nonbiologic processes.

Maloof, A. C.; Porter, S. M.; Moore, J. L.; Dudas, F. O.; Bowring, S. A.; Higgins, J. A.; Fike, D. A.; Eddy, M. P. (2010). "The earliest Cambrian record of animals and ocean geochemical change". Geological Society of America Bulletin. 122 (11–12): 1731–1774. Bibcode:2010GSAB..122.1731M. doi:10.1130/B30346.1.

"New Timeline for Appearances of Skeletal Animals in Fossil Record Developed by UCSB Researchers". The Regents of the University of California. 10 November 2010. Retrieved 1 September 2014.

Calibrating rates of early Cambrian evolution, Science 1993, 261(5126), s. 1293–1298. SA Bowring, JP Grotzinger, CE Isachsen, AH Knoll, SM Pelechaty, P Kolosov

Valentine, JW; Jablonski, D; Erwin, DH (1999). "Fossils, molecules and embryos: new perspectives on the Cambrian explosion". Development. 126 (5): 851–9. doi:10.1242/dev.126.5.851. PMID 9927587.

Budd, Graham (2013). "At the origin of animals: the revolutionary cambrian fossil record". Current Genomics. 14 (6): 344–354. doi:10.2174/13892029113149990011. PMC 3861885. PMID 24396267.

Erwin, D. H.; Laflamme, M.; Tweedt, S. M.; Sperling, E. A.; Pisani, D.; Peterson, K. J. (2011). "The Cambrian conundrum: early divergence and later ecological success in the early history of animals". Science. 334 (6059): 1091–1097. Bibcode:2011Sci...334.1091E. doi:10.1126/science.1206375. PMID 22116879. S2CID 7737847.

Kouchinsky, A.; Bengtson, S.; Runnegar, B. N.; Skovsted, C. B.; Steiner, M.; Vendrasco, M. J. (2012). "Chronology of early Cambrian biomineralization". Geological Magazine. 149 (2): 221–251. Bibcode:2012GeoM..149..221K. doi:10.1017/s0016756811000720.

Conway Morris, S. (2003). "The Cambrian "explosion" of metazoans and molecular biology: would Darwin be satisfied?". The International Journal of Developmental Biology. 47 (7–8): 505–15. PMID 14756326.

Butterfield, N.J. (2001). "Ecology and evolution of Cambrian plankton" (PDF). The Ecology of the Cambrian Radiation. New York: Columbia University Press. pp. 200–216. ISBN 978-0-231-10613-9. Retrieved 2007-08-19.

Bambach, R.K.; Bush, A.M.; Erwin, D.H. (2007). "Autecology and the filling of Ecospace: Key metazoan radiations". Palæontology. 50 (1): 1–22. doi:10.1111/j.1475-4983.2006.00611.x.

Budd, G. E.; Jensen, S. (2000). "A critical reappraisal of the fossil record of the bilaterian phyla". Biological Reviews of the Cambridge Philosophical Society. 75 (2): 253–95. doi:10.1111/j.1469-185X.1999.tb00046.x. PMID 10881389. S2CID 39772232.

Budd, G.E. (2003). "The Cambrian Fossil Record and the Origin of the Phyla". Integrative and Comparative Biology. 43 (1): 157–165. doi:10.1093/icb/43.1.157. PMID 21680420.

Wood, R.; Liu, A.G.; Bowyer, F.; Wilby, P.R.; Dunn, F.S.; Kenchington, C.G.; Cuthill, J.F.H.; Mitchell, E.G.; Penny, A. (2019). "Integrated records of environmental change and evolution challenge the Cambrian Explosion". Nature Ecology & Evolution. 3 (4): 528–538.

Jones, Daniel (2003) [1917], Peter Roach; James Hartmann; Jane Setter (eds.), English Pronouncing Dictionary, Cambridge: Cambridge University Press, ISBN 978-3-12-539683-8

Merriam-Webster

Whittington HB, Briggs DE (1985). "The largest Cambrian animal, Anomalocaris, Burgess Shale, British Columbia". Philosophical Transactions of the Royal Society B. 309 (1141): 569–609. Bibcode:1985RSPTB.309..569W. doi:10.1098/rstb.1985.0096.

Gould SJ (1989). Wonderful life: the Burgess Shale and the nature of history. New York: W.W. Norton. pp. 194–206. ISBN 978-0-393-02705-1.

Collins D (1996). "The "Evolution" of Anomalocaris and Its Classification in the Arthropod Class Dinocarida (nov.) and Order Radiodonta (nov.)". Journal of Paleontology. 70 (2): 280–293. doi:10.1017/S0022336000023362. JSTOR 1306391.

Whiteaves JF (1892). "Description of a new genus and species of phyllocarid Crustacea from the Middle Cambrian of Mount Stephen, B. C.". The Canadian Record of Science. 5 (4).

Conway Morris S (1978). "Laggania cambria Walcott: A Composite Fossil". Journal of Paleontology. 52 (1): 126–131. JSTOR 1303799.

Briggs DE (1979). "Anomalocaris, the largest known Cambrian arthropod". Palaeontology. 22 (3): 631–664.

Daley AC, Bergström J (June 2012). "The oral cone of Anomalocaris is not a classic peytoia". Die Naturwissenschaften. 99 (6): 501–4. Bibcode:2012NW.....99..501D. doi:10.1007/s00114-012-0910-8. PMID 22476406. S2CID 2042726

Vannier J, Liu J, Lerosey-Aubril R, Vinther J, Daley AC (May 2014). "Sophisticated digestive systems in early arthropods". Nature Communications. 5 (1): 3641. Bibcode:2014NatCo...5.3641V. doi:10.1038/ncomms4641. PMID 24785191.

De Vivo G, Lautenschlager S, Vinther J (16 December 2016). Reconstructing anomalocaridid feeding appendage dexterity sheds light on radiodontan ecology (Report).

De Vivo G, Lautenschlager S, Vinther J (July 2021). "Three-dimensional modelling, disparity and ecology of the first Cambrian apex predators". Proceedings. Biological Sciences. 288 (1955): 20211176. doi:10.1098/rspb.2021.1176. PMC 8292756. PMID 34284622.

Cong, Pei-Yun; Edgecombe, Gregory D.; Daley, Allison C.; Guo, Jin; Pates, Stephen; Hou, Xian-Guang (2018). "New radiodonts with gnathobase-like structures from the Cambrian Chengjiang biota and implications for the systematics of Radiodonta". Papers in Palaeontology. 4 (4): 605–621. doi:10.1002/spp2.1219. ISSN 2056-2802.

 Lerosey-Aubril, Rudy; Pates, Stephen (2018-09-14). "New suspension-feeding radiodont suggests evolution of microplanktivory in Cambrian macronekton". Nature Communications. 9 (1): 3774. doi:10.1038/s41467-018-06229-7. ISSN 2041-1723. PMC 6138677. PMID 30218075.

 Moysiuk, J.; Caron, J.-B. (2019-08-14). "A new hurdiid radiodont from the Burgess Shale evinces the exploitation of Cambrian infaunal food sources". Proceedings of the Royal Society B: Biological Sciences. 286 (1908): 20191079. doi:10.1098/rspb.2019.1079. PMC 6710600. PMID 31362637.

 Cong, Peiyun; Daley, Allison C.; Edgecombe, Gregory D.; Hou, Xianguang (2017-08-30). "The functional head of the Cambrian radiodontan (stem-group Euarthropoda) Amplectobelua symbrachiata". BMC Evolutionary Biology. 17 (1): 208. doi:10.1186/s12862-017-1049-1. ISSN 1471-2148. PMC 5577670. PMID 28854872.

 Cong, Peiyun; Daley, Allison C.; Edgecombe, Gregory D.; Hou, Xianguang; Chen, Ailin (September 2016). "Morphology of the radiodontan Lyrarapax from the early Cambrian Chengjiang biota". Journal of Paleontology. 90 (4): 663–671. doi:10.1017/jpa.2016.67. ISSN 0022-3360. S2CID 88742430.