Evolution Icon Evolution
Intelligent Design Icon Intelligent Design

Kimberella Is No Solution to the Cambrian Conundrum

Günter Bechly
Kimberella
Photo: Kimberella, by Ghedoghedo / CC BY-SA (https://creativecommons.org/licenses/by-sa/3.0).

Editor’s note: We have been delighted to present a series of posts by paleontologist Günter Bechly on the Ediacaran organism Kimberella. If identified as an animal, it would “predate the Cambrian explosion of bilaterian animal phyla as a kind of ‘advance guard.’” The question is of interest for debates about evolution and arguments about intelligent design raised by Stephen Meyer, among others. Find the full series about Kimberella here.

We can sum up that the current consensus suggests: that Kimberella is indeed a metazoan animal and most probably belongs either in the stem group of Bilateria or maybe has an uncertain position within Lophotrochozoa, but it is not a stem mollusk. Nevertheless, the proper interpretation of many of the structures of Kimberella is still controversial and the alternative possibility that Kimberella could be a coelenterate grade animal cannot be ruled out yet, especially since there is evidence for sclerotization and very diverse body plans in early Cambrian comb jellies (Scleroctenophora) (Zhao et al. 2019), as well as evidence for ancestral bilateral symmetry in Cnidaria (Erwin 2008).

Implications for the Cambrian Explosion

What does this tell us about the Cambrian explosion? Together with the alleged evidence for other Ediacaran bilaterian animals, which we critically discussed in my previous articles, this means that none of the Cambrian animal phyla is represented in the Ediacaran fossil record. This is very significant, because the potential soft-bodied ancestors would surely have been preserved in the numerous Ediacaran fossil localities of the Burgess Shale type (Bechly 2020), or in the Kimberella layers, which after all could preserve the soft-parts of a mollusk-like organism. At best the only two relatively uncontroversial Ediacaran bilaterians, Kimberella and the recently described worm-like Yilingia (Chen et al. 2019Evolution News 2019), could document the existence of just two phyla of Bilateria of uncertain affinity prior to the Cambrian era. However, their unique specializations strongly suggest that they could only represent extinct side branches but could not be directly ancestral to any of the numerous Cambrian animal phyla, and thus do not resolve their enigmatic origin.

Therefore, the latter still appear abruptly out of nowhere. The thousands of fossil links, postulated by Darwin’s theory of evolution, for the transition from a protist choanoflagellate ancestor to the complex body plans of the more than twenty Cambrian phyla of bilaterian metazoan animals, still remain elusive and missing, in spite of suitable fossil localities. Actually, the same problem exists for the so-called Avalon explosion that abruptly generated the diversity of macro-organisms of the Ediacaran biota. Where are all the missing links for the problematic organisms like CharniaDickinsonia, and Kimberella, which would document their gradual and stepwise evolution from protozoan ancestors?

Honest scientists cannot any longer ignore this substantial conflicting evidence. The fossil record speaks clearly and cries out loud: the history of life on Earth is a history of saltations. There is a reason why scientists called these abrupt appearances “explosions” or even “Big Bangs” of life. Guess which model better fits this evidence, Darwin’s theory of gradually “climbing mountain improbable” (a metaphor offered by Richard Dawkins) or rather intelligent design theory? It is not a difficult choice, unless your world view dictates what kind of theories are allowed.

References

  • Bechly G 2020. The demise of the Artifact Hypothesis. Evolution News July 6, 2020.
  • Bengtson S 2005. Mineralized skeletons and early animal evolution. pp. p. 101–124 in: Briggs DEG (ed). Evolving Form and Function: Fossils and Development: Proceedings of a Symposium Honoring Adolf Seilacher for his Contributions to Paleontology, in Celebration of his 80th Birthday. Peabody Museum of Natural History, Yale University, New Haven, CT, 288 pp. [Website]
  • Benton MJ, Donoghue PCJ, Asher RJ, Friedman M, Near TJ, Vinther J 2015. Constraints on the timescale of animal evolutionary history. Paleontologia Electronica 18(1), 1–107. [PDF]
  • Bottjer DJ 2002. Enigmatic Ediacara Fossils: Ancestors or Aliens? Chapter 2, pp. 11–33 in: Bottjer DJ, Etter W, Hagadorn JW, Tang CM (eds). Exceptional Preservation: A Unique View on the Evolution of Marine Life. Columbia University Press, New York, xv+403 pp. [PDF]
  • Bowyer F, Wood RA, Poulton SW 2017. Controls on the evolution of Ediacaran metazoan ecosystems: A redox perspective. Geobiology 15, 516–551. DOI: 10.1111/gbi.12232.
  • Brasier M 2009. Darwin’s Lost World: The Hidden History of Animal Life. Oxford University Press, Oxford, MA, xiv+304 pp. [Google Books]
  • Buatois LA, Narbonne GM, Mángano MG Carmona NB, Myrow P 2014. Ediacaran matground ecology persisted into the earliest Cambrian. Nature Communications 5:3544, 1–5. DOI: 10.1038/ncomms4544.
  • Budd GE 2008. The earliest fossil record of the animals and its significance. Philosophical Transactions of the Royal Society B 363(1496), 1425–1434 DOI: 10.1098/rstb.2007.2232.
  • Budd GE, Jensen S 2000. A critical reappraisal of the fossil record of the bilaterian phyla. Biological Reviews 75, 253–295. DOI: 10.1111/j.1469-185X.1999.tb00046.x.
  • Budd GE, Jensen S 2017. The origin of the animals and a ‘Savannah’ hypothesis for early bilaterian evolution. Biological Reviews 92(1), 446–473. DOI: 10.1111/brv.12239.
  • Butterfield NJ 2006. Hooking some stem-group “worms”: fossil lophotrochozoans in the Burgess Shale. Bioessays 28(12), 1161–1166. DOI: 10.1002/bies.20507.
  • Butterfield NJ 2008. An Early Cambrian Radula. Journal of Paleontology 82(3), 543–554. DOI: 10.1666/07-066.1.
  • Caron JB, Scheltema A, Schander C, Rudkin D 2006. A soft-bodied mollusc with radula from the Middle Cambrian Burgess Shale. Nature 442, 159–163. DOI: 10. 1038/nature04894.
  • Chen Z, Zhou C, Yuan X et al. 2019. Death march of a segmented and trilobate bilaterian elucidates early animal evolution. Nature 573, 412–415. DOI: 10.1038/s41586-019-1522-7.
  • Conway Morris S, Caron JB 2007. Halwaxiids and the Early Evolution of the Lophotrochozoans. Science315(5816), 1255–1258. DOI: 10.1126/science.1137187.
  • Coutts FJ 2019. Palaeoecology of Ediacaran communities from the Flinders Ranges of South Australia. Ph.D. thesis, University of Adelaide, 155 pp. [ResearchGate]
  • Coutts FJ, Gehling JG, García-Bellido DC 2016. How diverse were early animal communities? An example from Ediacara Conservation Park, Flinders Ranges, South Australia. Alcheringa: An Australasian Journal of Palaeontology 40(4), 407–421. DOI: 10.1080/03115518.2016.1206326.
  • Crimes TP 1994. The period of early evolution failure and the dawn of evolutionary success: the record of biotic changes across the Precambrian– Cambrian boundary. pp. 105–133 in: Donovan SK (ed). The Palaeobiology of Trace Fossils. John Wiley and Sons, New York, 308 pp. [Website]
  • Cunningham JA, Liu AG, Bengtson S, Donoghue PCJ 2017. The origin of animals: Can molecular clocks and the fossil record be reconciled? BioEssays 39(1), 1–12. DOI: 10.1002/bies.201600120.
  • Darroch SAF, Smith EF, Laflamme M, Erwin DH 2018. Ediacaran Extinction and Cambrian Explosion. Trends in Ecology & Evolution 33(9), 653–663. DOI: 10.1016/j.tree.2018.06.003.
  • Davidson EH, Erwin DH 2009. An Integrated View of Precambrian Eumetazoan Evolution. Cold Spring Harbor Symposia on Quantitative Biology 74, 65–80. DOI: 10.1101/sqb.2009.74.042.
  • Dornbos SQ, Bottjer DJ, Chen J-Y 2004. Evidence for seafloor microbial mats and associated metazoan lifestyles in lower Cambrian phosphorites of Southwest China. Lethaia 37(2), 127–137. DOI: 10.1080/00241160410004764 (there seems to be a DOI error with this article). [ResearchGate]
  • Droser ML, Gehling JG 2015. The advent of animals: The view from the Ediacaran. PNAS 112(16), 4865–4870. DOI: 10.1073/pnas.1403669112.
  • Droser ML, Tarhan LG, Gehling JG 2017. The Rise of Animals in a Changing Environment: Global Ecological Innovation in the Late Ediacaran. Annual Review of Earth and Planetary Sciences 45, 593–617. DOI: 10.1146/annurev-earth-063016-015645.
  • Dzik J 2003. Anatomical Information Content in the Ediacaran Fossils and Their Possible Zoological Affinities. Integrative & Comparative Biology 43(1), 114–126. DOI: 10.1093/icb/43.1.114.
  • Dzik J 2011. Possible Ediacaran ancestry of the halkieriids. Palaeontographica Canadiana 31, 205–217. [ResearchGate] [Abstract-Volume]
  • Erwin DH 1999. The origin of bodyplans. American Zoologist 39(3), 617–629. JSTOR: 3884441.
  • Erwin DH 2008. Wonderful Ediacarans, wonderful cnidarians? Evolution & Development 10(3), 263–264. DOI: 10.1111/j.1525-142X.2008.00234.x.
  • Erwin DH, Davidson EH 2002. The last common bilaterian ancestor. Development 129(13), 3021–3032. PMID: 12070079 [PDF].
  • Erwin DH, Laflamme M, Tweedt SM, Sperling EA, Pisani D, Peterson KJ 2011. The Cambrian Conundrum: Early Divergence and Later Ecological Success in the Early History of Animals. Science334, 1091–1097. DOI: 10.1126/science.1206375.
  • Erwin DH, Valentine, JW 2013. The Cambrian Explosion: The Construction of Animal Diversity. Roberts and Co., Calgary, 406 pp. [NHBS]
  • Evolution News 2015. Are the Ediacarans Transitional Forms for the Cambrian Explosion? Evolution News April 24, 2015.
  • Evolution News 2016. On the Cambrian Explosion, Keith Miller’s BioLogos White Paper Falls Short. Evolution News Dec. 29, 2016.
  • Evolution News 2019. Worming Evolution into the Cambrian Explosion. Evolution News Oct. 7, 2019.
  • Fedonkin MA 1980. New Precambrian Coelenterata in the north of the Russian platform. Paleontologicheskii Zhurnal 2, 7–15. [in Russian]
  • Fedonkin MA 1998. [A second birth of Kimberella]. Priroda 1, 3–10. [In Russian]
  • Fedonkin MA 2001. [Glimpse into 600 Million Years Ago]. Science in Russia 6 (126), 4–15. [In Russian]
  • Fedonkin MA 2003. The origin of the Metazoa in the light of the Proterozoic fossil record. Paleontological Research 7(1), 9–41. DOI: 10.2517/prpsj.7.9.
  • Fedonkin MA, Vickers-Rich P 2007. First trace of motion. pp. 205–216 in: Fedonkin MA, Gehling JG, Grey K, Narbonne GM, Vickers-Rich P (eds). The Rise of Animals – Evolution and Diversification of the Kingdom Animalia. John Hopkins University Press, Baltimore, MD, 326 pp. [Google Books]
  • Fedonkin MA, Waggoner BM 1997. The Late Precambrian fossil Kimberella is a mollusc-like bilaterian organism. Nature 388(6645), 868–871. DOI: 10.1038/42242.
  • Fedonkin MA, Gehling JG, Grey K, Narbonne GM, Vickers-Rich P 2007a. The Rise of Animals — Evolution and Diversification of the Kingdom Animalia. John Hopkins University Press, Baltimore, MD, 326 pp. [Google Books]
  • Fedonkin MA, Simonetta A, Ivantsov AY 2007b. New data on Kimberella, the Vendian mollusc-like organism (White Sea region, Russia): palaeoecological and evolutionary implications. pp. 157–179 in: Vickers-Rich P, Komarower P (eds). The Rise and Fall of the Ediacaran Biota. Geological Society, London, Special Publications 286. DOI: 10.1144/SP286.12.
  • Freeman G 2009. The rise of bilaterians. Historical Biology 21(1-2), 99–114. DOI: 10.1080/08912960903295843.
  • Gehling JG 1991. The case for Ediacaran fossil roots to the metazoan tree. Memoirs of the Geological Society of India 20, 181–224. [ResearchGate]
  • Gehling JG 1996. Taphonomy of the terminal Proterozoic Ediacara biota, South Australia. Unpublished Ph.D. thesis, Department of Earth and Space Sciences, University of California at Los Angeles, 222 pp. [ResearchGate]
  • Gehling JG 1999. Microbial mats in terminal Proterozoic siliciclastics: Ediacaran death masks. Palaios14, 40–57. DOI: 10.2307/3515360. [JSTOR]
  • Gehling JG, Droser M 2013. How well do fossil assemblages of the Ediacara Biota tell time? Geology 41(4), 447–450. DOI: 10 1130/G33881.1.
  • Gehling JG & Rigby JK 1996. Long Expected Sponges from the Neoproterozoic Ediacara Fauna of South Australia. Journal of Paleontology 70(2), 185–195. DOI: 10.1017/S0022336000023283.
  • Gehling JG, Runnegar B, Seilacher A 1995, Rasping marks of large, metazoan grazers, terminal Neoproterozoic of Australia and Late Cambrian? of Saudi Arabia. The 1st SEPM Congress on Sedimentary Geology, St. Petersburg, Florida, 57–58.
  • Gehling JG, Droser ML, Jensen SR, Runnegar BN 2005. Ediacara organisms: relating form to function. pp. 43–67 in: Briggs DEG (ed). Evolving Form and Function: Fossils and Development: Proceedings of a Symposium Honoring Adolf Seilacher for his Contributions to Paleontology, in Celebration of his 80th Birthday. Peabody Museum of Natural History, Yale University, New Haven, CT, 288 pp. [Website]
  • Gehling JG, Runnegar BN, Droser ML. 2014. Scratch Traces of Large Ediacara Bilaterian Animals. Journal of Paleontology 88(2), 284–298. DOI: 10.1666/13-054.
  • Giribet G, Edgecombe GD 2020. The Invertebrate Tree of Life. Princeton University Press, Princeton, NJ, 608 pp. [Google Books]
  • Glaessner MF, Daily B 1959. The Geology and Late Precambrian Fauna of the Ediacara Fossil Reserve. Records of the South Australian Museum 13, 369–401, pls xlii–xlvii. [BHL]
  • Glaessner MF 1960. Precambrian fossils from South Australia. Proceedings of the 21st International Geological Congress, Copenhagen, 22, 59–64.
  • Glaessner MF 1984. The Dawn of Animal Life: A Biohistorical Study. Cambridge University Press, Cambridge, 256 pp. [Google Books]
  • Glaessner MF, Wade M 1966. The Late Precambrian fossils from Ediacara, South Australia. Paleontology 9(4), 599–628, pls 97–103. [PDF]
  • Godfrey-Smith P 2016. Other Minds: The Octopus, the Sea, and the Deep Origins of Consciousness. Farrar, Straus and Giroux, New York, 272 pp. [Google Books]
  • Grazhdankin DV 2003. Structure and Depositional Environment of the Vendian Complex in the Southeastern White Sea Area. Stratigraphy and Geological Correlation 11(4) 313–331. [ResearchGate] [translated from Stratigrafiya, Geologicheskaya Korrelyatsiya 2003, 11(4), 3–24]
  • Grazhdankin D 2004. Patterns of distribution in the Ediacaran biotas: facies versus biogeography and evolution. Paleobiology 30(2), 203–221. DOI: 10.1666/0094-8373(2004)030<0203:PODITE>2.0.CO;2.
  • Grazhdankin D 2014. Patterns of Evolution of the Ediacaran Soft-Bodied Biota. Journal of Paleontology88(2), 269–283. DOI: 10.1666/13-072.
  • Ivantsov AY 2009. A New Reconstruction of Kimberella, a Problematic Vendian Metazoan. Paleontological Journal 43(6), 601–611. DOI: 10.1134/S003103010906001X. [original article in Russian in Paleontologicheskii Zhurnal 6, 3–12]
  • Ivantsov AY 2010a. The Metazoan Kimberella: Example of Vendian Fossils Interpretation. pp. 406–419 in: Tr. Mezhdunar. nauchn. konf. “Charl’z Darvin i sovremennaya biologiya”, 21– 23 sentyabrya 2009 g. (Charles Darwin and modern biology. Proc. Int. Sci. Conf., September 21–23, 2009), St. Petersburg. 
  • Ivantsov AY 2010b. Paleontological evidence for the supposed Precambrian occurrence of mollusks. Paleontological Journal 44(12), 1552–1559. DOI: 10.1134/S0031030110120105.
  • Ivantsov AY 2011. Feeding Traces of Proarticulata—the Vendian Metazoa. Paleontological Journal 45(3), 237–248. DOI: 10.1134/S0031030111030063.
  • Ivantsov AY 2012. Paleontological Data on the Possibility of Precambrian Existence of Mollusks. Chapter 5 pp. 153-179 in: Fyodorov A, Yakovlev H (ed). Mollusks: Morphology, Behavior and Ecology. Nova Science Publ., Hauppauge, NY, 285 pp. [ResearchGate]
  • Ivantsov AY 2013. Trace Fossils of Precambrian Metazoans “Vendobionta” and “Mollusks”. Stratigraphy and Geological Correlation 21(3), 252–264. DOI: 10.1134/S0869593813030039.
  • Ivantsov AY 2017. The most probable Eumetazoa among late Precambrian macrofossils. Invertebrate Zoology 14(2), 127–133. DOI: 10.15298/invertzool.14.2.05.
  • Ivantsov AX, Fedonkin MA 2001a. [Traces of Active Movement – Final Proof for the Animal Nature of Ediacaran Organisms]. pp. 133–137 in: Materialy II Mezhdunarodnogo simpoziuma Evolyutsiya zhizini na Zemle [Proceedings of the Second International Symposium “Evolution of Life on Earth”]. Izd. Nauchno-Tekh. Lit-ry (NTL), Tomsk. [In Russian]
  • Ivantsov AY, Fedonkin MA 2001b. Locomotion Trails of the Vendian Invertebrates Preserved with the Producer’s Body Fossils, White Sea, Russia. Abstracts of the North American Paleontological Convention 2001. PaleoBios 21, 72. [Abstract]
  • Ivantsov AY, Malakhovskaya YE, Serezhnikova EA 2004. Some Problematic Fossils from the Vendian of the Southeastern White Sea Region. Paleontological Journal 38(1), 1–9. [ResearchGate]
  • Ivantsov AY, Leonov M, Zakrevskaya M 2007. Guidebook of the field paleontological excursion: Zimnie Gory – locality of the Vendian (Ediacaran) soft-bodied animals. The Rise and Fall of the Vendian/Ediacaran Biota: Origin of the Modern Biosphere. International Conference on the IGCP Project 493. PIN RAS, Moscow, 27 pp. [ResearchGate]
  • Ivantsov AY, Nagovitsyn A, Zakrevskaya M 2019. Traces of Locomotion of Ediacaran Macroorganisms.Geosciences 9(9), 395), 1–11. DOI: 10.3390/geosciences9090395.
  • Jenkins RJF 1984. Interpreting the oldest fossil cnidarians. Palaeontographica Americana 54, 95–104. [BHL]
  • Jenkins RJF 1992. Functional and Ecological Aspects of Ediacaran Assemblages. Chapter 5 pp. 131–176 in: Lipps JH, Signor PW (eds). Origin and Early Evolution of the Metazoa. Topics in Geobiology, vol 10. Plenum Press, New York, xiii+570 pp. DOI: 10.1007/978-1-4899-2427-8_5.
  • Jenkins RJF 1995. The problems and potential of using animal fossils and trace fossils in terminal Proterozoic biostratigraphy. Precambrian Research 73(1-4), 51–69. DOI: 10.1016/0301-9268(94)00071-X.
  • Jenkins RJF, Ford CH, Gehling JG 1983. The Ediacara Member of the Rawnsley Quartzite: the context of the Ediacara assemblage (late Precambrian, Flinders Ranges). Journal of the Geological Society of Australia 30(1-2), 101–119. DOI: 10.1080/00167618308729240.
  • Knaust D 2015. Grazing traces (Kimberichnus teruzzii) on Middle Triassic microbial matground. pp. 115–125 in: McIlroy D (ed). ICHNOLOGY: Papers from ICHNIA III in St. John’s, NL, Canada. Geological Association of Canada, Miscellaneous Publication 9. [CD-ROM] [ResearchGate]
  • Knoll AH 2011. The Multiple Origins of Complex Multicellularity. Annual Review of Earth and Planetary Sciences 39, 217–239. DOI: 10.1146/annurev.earth.031208.100209.
  • Kocot KM 2013. Recent advances and unanswered questions in deep molluscan phylogenetics. American Malacological Bulletin 31(1), 195–208. DOI: 10.4003/006.031.0112.
  • Kocot KM, Poustka AJ, Stöger I, Halanych KM, Schrödl M 2020. New data from Monoplacophora and a carefully-curated dataset resolve molluscan relationships. Scientific Reports 10:101, 1–8. DOI: 10.1038/s41598-019-56728-w.
  • Laflamme M, Darroch SAF, Tweedt SM, Peterson KJ, Erwin DH 2013. The end of the Ediacara biota: Extinction, biotic replacement, or Cheshire Cat? Gondwana Research 23(2), 558–573. DOI: 10.1016/j.gr.2012.11.004.
  • Larson D 2020. Kimberella as a stemgroup mollusc. Fossil Hunters Feb. 10, 2020.
  • Martin MW, Grazhdankin DV, Bowring SA, Evans DAD, Fedonkin MA, Kirschvink JL 2000. Age of Neoproterozoic Bilatarian Body and Trace Fossils, White Sea, Russia: Implications for Metazoan Evolution. Science 288(5467), 841–845. DOI: 10.1126/science.288.5467.841.
  • McMenamin MAS 2016. Dynamic Paleontology: Using Quantification and Other Tools to Decipher the History of Life. Springer, Cham, xii+251 pp. DOI: 10.1007/978-3-319-22777-1. [PDF of Systematics section]
  • McMenamin MAS 2018. Clemente Biota. pp. 61–102 in: Deep Time Analysis: A Coherent View from the History of Life. Springer, Cham, 288 pp. DOI: 10.1007/978-3-319-74256-4_3. [Google Books] [PDF of Systematics section]
  • Meyer SC 2013. Darwin’s Doubt. HarperOne, viii+498 pp.
  • Mitchell EG, Bobkov N, Bykova N, Dhungana A, Kolesnikov A, Hogarth IRP, Liu AG, Mustill TMR, Sozonov N, Xiao S, Grazhdankin DV 2020. The influence of environmental setting on the community ecology of Ediacaran organisms. Interface Focus 10(4):20190109, 1–14. DOI: 10.1098/rsfs.2019.0109.
  • Muscente AD, Bykova N, Boag TH et al. 2019. Ediacaran biozones identified with network analysis provide evidence for pulsed extinctions of early complex life. Nature Communications 10:911, 1–15. DOI: 10.1038/s41467-019-08837-3.
  • Nielsen C 2001. Animal Evolution. Oxford University Press, 563 pp. (1st Edition).
  • Nielsen C 2012. Animal Evolution: Interrelationships of the Living Phyla. 3rd Edition. Oxford University Press, 402 pp. [Google Books]
  • Parkhaev P 2008. The Early Cambrian Radiation of Mollusca. Chapter 3 pp. 33-69 in: Ponder WF, Lindberg DR (eds). Phylogeny and Evolution of the Mollusca. University of California Press, Berkeley, 469 pp. DOI: 10.1525/california/9780520250925.003.0003.
  • Parkhaev PY 2017. Origin and the Early Evolution of the Phylum Mollusca. Paleontological Journal51(6), 663–686. DOI: 10.1134/S003103011706003X.
  • Peterson KJ, Cotton JA, Gehling JG, Pisani D 2008. The Ediacaran emergence of bilaterians: congruence between the genetic and the geological fossil records. Philosophical Transactions of the Royal Society B 363(1496), 1435–1443. DOI: 10.1098/rstb.2007.2233.
  • Ponder WF, Lindberg DR (eds) 2008. Phylogeny and Evolution of the Mollusca. University of California Press, Berkeley, 469 pp. [Google Books]
  • Retallack GJ 2013. Ediacaran life on land. Nature 493, 89–92. DOI: 10.1038/nature11777.
  • Rozhnov SV 2010. From Vendian to Cambrian: the Beginning of Morphological Disparity of Modern Metazoan Phyla. Russian Journal of Developmental Biology 41(6), 357–368. DOI: 10.1134/S1062360410060032.
  • Scheltema AH 2014. The original molluscan radula and progenesis in Aplacophora revisited. Journal of Natural History 48(45-48), 2855–2869, DOI: 10.1080/00222933.2014.959573.
  • Scheltema AH, Schander C 2006. Exoskeletons: Tracing Molluscan Evolution* Venus 65(1-2), 19–26. DOI: 10.18941/venus.65.1-2_19.
  • Scherholz M, Redl E, Wollesen T, Todt C, Wanninger A 2013. Aplacophoran Mollusks Evolved from Ancestors with Polyplacophoran-like Features. Current Biology 23(21), P2130–P2134. DOI: 10.1016/j.cub.2013.08.056.
  • Schrödl M, Stöger I 2014. A review on deep molluscan phylogeny: old markers, integrative approaches, persistent problems. Journal of Natural History 48(45-48), 2773–2804. DOI: 10.1080/00222933.2014.963184.
  • Seilacher A 1997. Fossil Art: An Exhibition of the Geologisches Institut Tuebingen. The Royal Tyrrell Museum of Paleontology, Drumheller, Alberta, Canada, 64 pp. [Review]
  • Seilacher A 1999. Biomat-Related Lifestyles in the Precambrian. Palaios 14(1), 86–93. JSTOR: 3515363.
  • Seilacher A 2007. Trace Fossil Analysis. Springer Science, Berlin, 226 pp. [Google Books]
  • Seilacher A, Hagadorn JW 2010. Early molluscan evolution: Evidence from the trace fossil record. Palaios 25, 565–575. JSTOR: 40865490.
  • Seilacher A, Grazhdankin D, Legou A 2003. Ediacaran biota: The dawn of animal life in the shadow of giant protists. Paleontological Research 7(1), 43–54. DOI: 10.2517/prpsj.7.43.
  • Seilacher A, Buatois LA, Mángano MG 2005. Trace fossils in the Ediacaran–Cambrian transition: Behavioral diversification, ecological turnover and environmental shift. Palaeogeography Palaeoclimatology Palaeoecology 227, 323–356. DOI: 10.1016/j.palaeo.2005.06.003.
  • Serezhnikova EA 2007. Palaeophragmodictya spinosa sp. nov., a Bilateral Benthic Organism from the Vendian of the Southeastern White Sea Region. Paleontological Journal 41(4), 360–369. DOI: 10.1134/S0031030107040028.
  • Shanker R, Mathur VK 1992. Precambrian-Cambrian sequence in Krol Belt and additional Ediacaran fossils. Geophytology 22, 27–39.
  • Shu D, Isozaki Y, Zhang X, Han J, Maruyama S 2014. Birth and early evolution of metazoans. Gondwana Research 25, 884–895. DOI: 10.1016/j.gr.2013.09.001.
  • Shukla M, Babu R, Singh VK, Sharma M 2006. A Catalogue of Precambrian Palaeobiology from India. Diamond Jubilee Special Publication. Birbal Sahni Institute of Palaeobotany, Lucknow, 121 pp. [ResearchGate]
  • Sigwart JD, Lindberg DR 2015. Consensus and Confusion in Molluscan Trees: Evaluating Morphological and Molecular Phylogenies. Systematic Biology 64(3), 384–395. DOI: 10.1093/sysbio/syu105.
  • Smith MR 2012. Mouthparts of the Burgess Shale fossils Odontogriphus and Wiwaxia: implications for the ancestral molluscan radula. Proceedings of the Royal Society B 279(1745), 4287–4295. DOI: 10.1098/rspb.2012.1577.
  • Sperling EA, Vinther J 2010. A placozoan affinity for Dickinsonia and the evolution of late Proterozoic metazoan feeding modesEvolution & Development 12, 201–209, doi: 10.1111/j.1525-142X.2010.00404.x.
  • Sperling EA, Knoll AH, Girguis PR 2015. The ecological physiology of Earth’s second oxygen revolution. Annual Review of Ecology, Evolution, and Systematics 46, 215–235. DOI: 10.1146/annurev-ecolsys-110512-135808.
  • Stearley R 2013. The Cambrian Explosion: How Much Bang for the Buck? Perspectives on Science and Christian Faith 65(4), 245–257. [PDF]
  • Stöger I, Sigwart JD, Kano Y, Knebelsberger T, Marshall BA, Schwabe E, Schrödl M 2013. The Continuing Debate on Deep Molluscan Phylogeny: Evidence for Serialia (Mollusca, Monoplacophora + Polyplacophora). BioMed Research International 2013: 407072, 1–18. DOI: 10.1155/2013/407072.
  • Sutton MD, Briggs DEG, Siveter DJ, Siveter DJ, Sigwart JD 2012. A Silurian armoured aplacophoran and implications for molluscan phylogeny. Nature 490, 94–97. DOI: 10.1038/nature11328.
  • Tarhan LG, Droser ML, Gehling JG 2015. Depositional and preservational environments of the Ediacara Member, Rawnsley Quartzite (South Australia): Assessment of paleoenvironmental proxies and the timing of ‘ferruginization’. Palaeogeography, Palaeoclimatology, Palaeoecology 434, 4–13. DOI: 10.1016/j.palaeo.2015.04.026.
  • Telford MJ, Littlewood DTJ (eds) 2008. Animal Evolution: Genomes, Fossils, and Trees. Oxford University Press, Oxford, xvi+245 pp, 11 pls. [Google Books, includes the papers by Budd 2008 and Peterson et al. 2008]
  • Trusler P, Stilwell J, Vickers-Rich P 2007. Comment: future research directions for further analysis of Kimberella. pp. 181-185 in: Vickers-Rich P, Komarower P (eds). The Rise and Fall of the Ediacaran Biota. Geological Society, London, Special Publications 286. DOI: 10.1144/SP286.13.
  • Valentine JW 2004. On the Origin of Phyla. University of Chicago Press, Chicago and London, 614 pp. [Google Books]
  • Vaziri SH, Majidifard MR, Laflamme M 2018. Diverse Assemblage of Ediacaran fossils from Central Iran. Scientific Reports 8:5060, 1–7. DOI: 10.1038/s41598-018-23442-y.
  • Vendrasco MJ 2012. Early evolution of molluscs. pp. 1–43 in Fyodorov A, Yakovlev H (eds). Mollusks: morphology, behavior and ecology. Nova Science Publishers, Hauppauge, NY, 285 pp.
  • Vinther J 2014. A molecular palaeobiological perspective on aculiferan evolution, Journal of Natural History 48(45–48), 2805–2823, DOI: 10.1080/00222933.2014.963185.
  • Vinther J 2015. The Origins of Molluscs. Palaeontology 58(1), 19–34. DOI: 10.1111/pala.12140.
  • Vinther J, Sperling EA, Briggs DE, Peterson KJ 2012. A molecular palaeobiological hypothesis for the origin of aplacophoran molluscs and their derivation from chiton-like ancestors. Proceedings of the Royal Society B 279(1732), 1259–1268. DOI: 10.1098/rspb.2011.1773.
  • Vinther J, Parry L, Briggs DEG, Van Roy P 2017. Ancestral morphology of crown-group molluscs revealed by a new Ordovician stem aculiferan. Nature 542, 471–474. DOI: 10.1038/nature21055.
  • Wade M 1972. Hydrozoa and Scyphozoa and other medusoids from the Precambrian Ediacara fauna, South Australia. Palaeontology 15(2), 197–225, pls 40–43. [PDF]
  • Waggoner B 1998. Interpreting the Earliest Metazoan Fossils: What Can We Learn? American Zoologist38(6), 975–982. JSTOR: 4620224.
  • Wanninger A, Wollesen T 2019. The evolution of molluscs. Biological Reviews of the Cambridge Philosophical Society 94(1), 102–115. DOI: 10.1111/brv.12439.
  • Xiao S, Laflamme M 2009. On the eve of animal radiation: phylogeny, ecology and evolution of the Ediacara biota. Trends in Ecology and Evolution 24(1), 31–40. DOI: 10.1016/j.tree.2008.07.015.
  • Zhao Y, Vinther J, Parry LA, Wei F, Green E, Pisani D, Hou X, Edgecombe GD, Cong P 2019. Cambrian Sessile, Suspension Feeding Stem-Group Ctenophores and Evolution of the Comb Jelly Body Plan. Current Biology 29, 1112–1125. DOI: 10.1016/j.cub.2019.02.036.