Mass Extinctions, Evolutionary Leaps, and the Virus-Information Connection

Short of time, still I’ve glanced the interesting chapter 3 posted here. It seems a nice book. Also, its style of writing is clear and accessible to most world readers; congratulations.

Very likely I should read more before asking, even so, why is counted the current extinction as “6th”? Considering a 27my-cycle for great mass-extinctions, where/when is the starting-point? I would chance it as 250 mya! though I’ve noticed the mentioned earlier extinctions as well.

Furthermore, as written, the connection of mass extinctions with the brown companion and then the latter causing meteor rain turned up a pretty much ground-worked case. Yet —again, perhaps I need to read the rest of the book, or this is not the focus of the book— what is the relation of these extinctions with earth-changes? And —though I noticed the mentioned “virus changer” as something introduced under these “rains”— interconnected with earth-changes can we see also the human psychic (synchronically?) merged with cosmic events (cycles, etc.)?!!


So, above is recalled the transcripts, and the nature of the 3D reality is synthetized very well. That is to say, it’s not only that outer cosmic events provoke earth-changes… actually the —collective?— human mind also can provoke earth-changes. And “earth-changes” go until what distance? How is defined our earth-kingdom? This needs contemplation, but I’m also pinpointing another aspect that I’ll comment more in the next post.​

All your questions are answered in the book.
 
Let’s wonder for a moment that cyclic 27my extinctions are also related to the human mind. Well, mankind has a lame main-stream history at maximum limited to the Holocene (last 10,000 years), but with humanoid fossils spanning the Quaternary —last 2 million years— and a few findings within the last parts of the Cenozoic. So? Well, maybe not properly “human” but maybe some “proto-human” mind acting from some density is linked to the realm of earth events. For example, in the transcripts at some point Laura asked if humans lived in the time of dinosaurs. Surprisingly the C’s answered “Yes” though under a transitional period that “soon” vanished. So, why could not the “mind” be related to all the extinctions of eons ago?!! Another “odd” question: The “brown-twin” does seem the cause of comet rain, but what did cause the “brown-twin”? Maybe it helps if recalled that out of the 3rd density “time is meaningless”?!!

Moreover, with regard to the tectonic changes (during these cosmic events of extinctions?!!), they seem important —IMOP— because such changes likely should be registered somehow also in the memories of the timeless soul, and these in turn could reflect in dreams and ancient records —oral and in writings— from around the world even if humankind wasn’t physically present during those events. Thus, events of Pangaea or Gondwana may be available via myths and old songs. Notice that the C’s said that, after this “present,” earth will be different in terms of continental lands. So, in a certain way we could be “re-living” a paleo-myth right now.

An interesting latest vid by Adapt 2030 in which he foresees Oct. 2024 as a possible repeat of 79AD & 1486AD with regards to the Exact squaring of the outer four planets and the potential effect on Earth.

 

Part II: Life Explosions​



fossils-png-olenellus-trilobite.png

© Wikimedia Common
Fossil of Trilobite Walliserops trifurcatus


Chapter 4: Peculiar Life-Forms around Cometary Impacts​


Logically one considers cometary event as solely agents of mass destruction as exemplified by the numerous mass extinctions or the induced catastrophes like volcanism or seismicity described in the first part. But while writing “Cometary Encounter”, I stumbled upon some peculiarities relating to the Tunguska event[1] and its effects on local life forms:

It was found that the genotypic dispersion has sharply increased in the Tunguska trees. The effect is prominent, has a patchy character and concentrates toward the epicenter area, as well as toward of the TSB [Tunguska Space Body] trajectory projection (Vasilyev 1999, 2000, 1998). At maximums the genotypic dispersion shows about 12-fold increment (Vasilyev 2000). One of the maximums coincides again with the Mount Chirvinskii, another - with the calculated center of the light flash.[2]

The term “genotypic dispersion” used above refers to an increase in genetic mutations. Mutations, especially detrimental ones, are compatible with cometary encounters being exclusively agents of destruction since radioactive fallouts and ionizing radiations[3] are known to damage genetic material[4] and occurred during the Tunguska explosion[5]. But Tunguska trees revealed another feature that is even more peculiar:

The cause of the anomalous growth of tree rings after 1909 is more controversial. We collected tree ring data for 9 spruces, 1 larch and 1 Siberian pine. A comparison of the average tree ring width over about 30 years before 1907 and exactly the same period after 1909 has confirmed the width increase for all the 11 trees examined.
From these data no correlation with the tree position has been found. The trees were divided into two groups: 5 trees with an average ring width before 1907 equal to about 0.4 mm and a second group with a ring width of about 1 mm. After 1909 both groups reach approximately the same ring width of about 1.2-1.5 mm with an increase for the first group by a factor 3-4, as against a factor 1.2-1.5 for the second group.[6]

Notice that this growth spur affected both new trees, young trees and old trees. This accelerated growth only weakened in the 1990s[7]. A sustained and accelerated growth doesn’t sound like a random mutation, which is in more than 99.99%[8] of the cases detrimental or neutral. It sounds rather like a beneficial one. Could cometary events, beside their obvious destructive effects, somehow improve life forms?

tunguska tree bw.jpg

© Vitaly Romeyko
Cross section of a Tunguska tree. The black arrow shows the year 1908.
The rings after the event markedly wider

Another puzzling feature revealed by the Tunguska trees is that the area of maximum growth is away from the epicenter:

[Trees growth] extrapolated maximum is expected far away from the epicenter, at some 20-25 km distance (Emelyanov et al. 1979, Vasilyev 1999). One has an impression that the flight of the TSB was accompanied by some unknown agent capable to induce remote ecological and maybe even genetic changes.[9]

Along trees, insects in Tunguska were also affected by the overhead explosion:

[…] geneticists V. K. Dmitrienko and 0 . P. Fedorova found that the insects living near Ostraya Mountain and at Churgim Creek did sharply differ from those caught in other places. In other words, these differences were greatest where peaks of mutations in local pines were also greatest. This seems to be significant. It would therefore seem that the ancestors of these ants did also undergo mutations at the Tunguska catastrophe of 1908 [10]

In addition to be the place of unexpected occurrence of beneficial mutations, Tunguska, although it’s a very common biotope (taiga forest) which is not isolated whatsoever by surrounding seas, deserts or mountains, is the location of a few plants that are found nowhere else in the world:

Most endemics are protected only in a few nature reserves around the globe - because these species simply do not exist elsewhere. Examples of this group of plants include the Catang's Oxytrope, found only in Central Siberia, and Iris of Bludov [Iris bloudowii}], found only in southern Siberia - the Tunguska Reserve is located at the northernmost limit of the distribution range of this species. Both of these species are included in the Red Books of the Krasnoyarsk Territory.
However, the most interesting endemic found here in the Tunguska Nature Reserve is Astragalus of Shumilov [Astragalus schumilovae]. This plant can survive in only one place on the entire globe - in southern Evenkia, between the rivers Podkamennaya Tunguska and Chunya. Thus, the only reserve in the world that protects this fantastically rare species is the Tunguska Nature Reserve.[11]

Even Humans in the vicinity of Tunguska also experienced non-detrimental and extremely rare mutations:

Rychkov discovered an Evenk woman lacking the Rh-D antigen. Genetic examinations of her family enabled to conclude that a very rare mutation of the Rh-D gene happened in 1912. This mutation may have affected the women’s parents, who in 1908 lived at some 100 km distance from the epicenter and were eyewitnesses of the Tunguska explosion. The women remembered her parents’ impressions of the event: a very bright flash, a clap of thunder, a droning sound, and a burning wind (Rychkov 2000).[12]

Notice that the woman in question was from the Evenk, an indigenous people of Russia where more than 99% of the population has a positive rhesus[13].

Now, is Tunguska an isolated oddity or can we find other examples of new life forms spawning from documented cometary impact? To answer this question, let’s have a look at the most recent major cometary bombardment, the one that started the Younger Dryas ca. 12,900 BP.

The Carolina Bays are the ejecta impact sites of the primary cometary impact in Lake Michigan[14], they tell a fascinating story that is surprisingly similar to Tunguska:

Much to everyone's amazement, Venus' flytraps are not some strange, exotic plant. It is native only to the Carolinas, and, according to Wikipedia, probably within a 60-mile radius of Wilmington, North Carolina. They are found mostly around crater-like formations known as Carolina Bays, which are located mostly in the same area. Connections to these bays, which are thought to be caused by meteors, only help theories of their alien origins.[15]

While there are about 180 species[16] of carnivorous plant belonging to the Droseraceae family, Venus’ flytraps (Dionaea muscipula) are the only specie representative of the genus Dionaea.

The closest relative[17] of the Venus flytrap is a water plant called waterwheel (Aldrovanda vesiculosa), which is the only plant sharing the same snap trap mechanism[18].

Despite sharing a similar snap trap mechanism, the Venus flytrap and the waterwheel are genetically extremely different:

The genome size of both cultured and wild Dionaea muscipula is 3.18 Gbp[19] and thus comparable in size with the human genome. In contrast, the genome sizes obtained for Aldrovanda vesiculosa are 509 Mbp[20]

As you can see in the picture below, there are indeed more than a few “random” mutations between the two alleged cousins:

Genomes of the Venus Flytrap and Close Relatives.jpg
© Palfalvi
A (left): Water plant waterwheel (Aldrovanda vesiculosa)
B (right): Ground plant Venus flytrap (Dionaea Muscipula)

Given the sudden and localized apparition of Venus flytrap out of thin air, it’s not surprising that Charles Darwin euphemistically coined the Venus flytrap as “one of the most wonderful [plant] in the world”[21]. He was certainly smart enough not to mention the serious challenges that Venus’ flytraps posed to his claims bout incremental minute evolution caused by random mutations.

Actually, the Venus’ flytraps are only one example of species that are exclusively endemic to the Carolina Bays:

Although most Carolina bays are much smaller, Lake Waccamaw in North Carolina stretches across 9,000 acres with 14 miles of shoreline at the headwaters of the Waccamaw River. It is home to native fish and plants that can only be found in or around the lake.[22]

Naturalist Janna Sasser provides more details about the endemic, rare or endangered species of plants and animals found in the Carolina Bays:

For Terri Kirby Hathaway, North Carolina Sea Grant’s marine education specialist, the bays’ value as a habitat for many of the state’s rare plant and animal species is clear. [...] While other natural landscapes of the Americas were being named and noted, these low wetlands — unique reservoirs housing a wealth of beautiful and unfamiliar plant and animal species — remained inconspicuous. [...] Yet, she points out that unaltered bays function as wildlife habitat for several endangered animals and rare plants, and support an array of unique communities of species. [...]
Along with five species on the state’s rare plant list — the Venus-hair fern, green-fly orchid, seven-angled pipewort, narrowleaf yellow pondlily and water arrowhead — Hall notes seven animal species endemic to Lake Waccamaw. [...]
As of 2004, seven rare animals and 10 rare plants were documented residing in the bay, including one Federally Endangered species and two Federal Species of Concern.[23]

The Carolina bays host a number a fauna and flora species found nowhere on our planet. This peculiarity begs an obvious question: “did the cometary ejecta that formed the Carolina Bays contribute to the apparition of new and endemic species?”



[1] Overhead cometary explosion above Tunguska, Russia in 1908.
[2] Vasilyev, N. V. (1999). “Ecological consequences of the Tunguska catastrophe”, in Problemi radioekologii i pogranichnikh discipline, 89
[3] Cravens, T., et al. (1987) “Electron impact ionization in the vicinity of comets”. Journal of Geophysical Research 92, 7341–7353
[4] National Research Council (US) Committee on the Biological Effects of Ionizing Radiation. (1990). “Health Effects of Exposure to Low Levels of Ionizing Radiation”. National Academies Press
[5] Rubtsov, V. (2012) “Reconstruction of the Tunguska Event of 1908: Neither an Asteroid, Nor a Comet Core”. arXiv:1302.6273
[6] See: Longo, G. et al. (1994) “Search for microremnants of the Tunguska cosmic body”. Planetary and Space Science. n. 2, 163--177
Serra, R. et al. (1994) “Experimental hints on the fragmentation of the Tunguska cosmic body”. Planetary and Space Science, n. 9, 777--783
[7] Longo, G., et al. (1995) “Some Answers From Tunguska Mute Witnesses“ in Meteorite!, 1 (4), 12
[8] Jesse D. Bloom, Frances H. Arnold. (2009) “In the light of directed evolution: Pathways of adaptive protein evolution”. Proceedings of the National Academy of Sciences 106 (Supplement 1) 9995-10000
[9] Zurab K. Silagadze (2003) “Tunguska genetic anomaly and electrophonic meteors”. Acta Phys.Polon. B 36 935
[10] Rubtsov, Vladimir. (2009) “The Tunguska Mystery”. Springer Science & Business Media
[11] Wildnet Editors. (2020) “Rare plants”. Wildnet.ru (translated from Russian)
[12] Zurab K. Silagadze (2003) “Tunguska genetic anomaly and electrophonic meteors”. Acta Phys.Polon. B 36 935
[13] Gafarov NI, et al. (1998) “Genetic characteristics of the population of Severo-Baĭkal'skiĭ region of the northern part of the Buryat Republic”. Genetika;34(7):979-84
[14] Lescaudron, Pierre. (2021) “Cometary Encounters”. Red Pill Press. Chapter “Atmospheric ablation induced by a cometary impact”
[15] Everything is electric Editors (2015). "Flytraps are Venus’?”. Everythingiselectric.com
[16] Christenhusz, M. et al. (2016) "The number of known plants species in the world and its annual increase". Phytotaxa. Magnolia Press. 261 (3): 201–217
[17] Gibson, T. et al. (2009) "Evolving Darwin's 'most wonderful' plant: ecological steps to a snap-trap". New Phytologist. 183 (3): 575–587
[18] Cameron, K. et al. (2002) "Molecular evidence for the common origin of snap-traps among carnivorous plants". American Journal of Botany. 89 (9): 1503–1509
[19] Gbp stands for Giga base pair, referring to the pairs of bases (nucleotides: A,T,G,C) that constitute DNA.
[20] Palfalvi et al. (2020) “Genomes of the Venus Flytrap and Close Relatives Unveil the Roots of Plant Carnivory” Curr Biol. 22;30(12):2312-2320
[21] Darwin, C. (1875), “Insectivorous Plants”, John Murray
[22] American Rivers Editors (2020). “What are Carolina Bays”. American Rivers
[23] Sasser, Janna. (2015) “Naturalist’s notebook: Carolina Bays: Another Man’s Treasure”. North Carolina State University
 
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Chapter 5: The K/T Boundary​


Could cometary-induced mass extinction also “improve” existing life forms? After all, maybe Tunguska and the Carolina Bays were isolated cases, and these are not mass extinction events per se.

So, let’s have a look at the most recent documented comet-induced mass extinction, the K/T boundary[1] when 66 million years ago, the Chicxulub impact wiped out the dinosaurs along with 75%[2] of all species on the planet as shown by the black arrow in the cyclical cometary extinction diagram above[3].

The K/T boundary is a geological term referring to a very thin stratum[4] of clay, suggesting a brief but marked disruption. It is shown by the white arrow in the picture below. The K/T boundary is sandwiched right below the sediments of the Cretaceous, the one from Tertiary right above it[5]:

pic191-K-T-boundary.jpg
© Creative Commons
The K/T boundary

Right below the K/T boundary lay the fossils of the dinosaurs and right above the K/T boundary – meaning right after the mass extinction – lay the fossils of fully developed new species with no known ancestors:

Immediately following the end-Cretaceous, primitive birds enjoyed a surge of development, and large flightless birds like today's ostrich suddenly appeared. Tree sloths, armadillos and anteaters saw dramatic development, as did egg-laying mammals such as the platypus and the echidnor. Other mammals, until then not much bigger than a house cat, took off in a rapid and spectacular diversification, all with no known ancestors.[6]

Adding to this impressive list of new complex species mentioned in the above quote, the aftermath of the K/T extinction also witnessed the sudden apparition of the first marsupials[7], the first odd-toed ungulates[8], a taxonomic order that contains for example the horses, the rhinoceroses and the tapirs. Soon after the K/T extinction also appeared the first whales[9], the first bats[10], the first carnivorous mammals[11] and the first primates[12].

The K/T extinction marked the beginning of the explosive evolution of all the modern species of birds[13] and of the spiny finned teleost fishes that represent one third of all living vertebrates[14].

The illustration below shows that most marine and land modern mammals appeared around the time of the K/T extinction:

20 million years of rapid diversification2.jpg
© Michael Novacek
Apparition of numerous modern mammals around the time of the K/T extinction



[1] Cretaceous/Tertiary
[2] Kaiho, K. et al. (2016) “Global climate change driven by soot at the K-Pg boundary as the cause of the mass extinction”. Sci Rep 6, 28427
[3] See chapter 1 “Mass extinctions“
[4] About 1,2 cm (half an inch)
[5] It is abbreviated K (as in "K-Pg boundary") for its German translation "Kreide" (chalk)
See: Geology Editors (2014) “Cretaceous Period” geology.com
[6] Felix, Robert (2008). “Magnetic Reversals and Evolutionary Leaps: The True Origin of Species”. Sugarhouse Publications p33
[7] O'Leary et al. (2013) "The Placental Mammal Ancestor and the Post–K-Pg Radiation of Placentals". Science. 339 (6120): 662–667
[8] Halliday Thomas et al. (1833) "Eutherians experienced elevated evolutionary rates in the immediate aftermath of the Cretaceous–Palaeogene mass extinction" Proceedings of the Royal Society B: Biological Sciences. 283 (1833): 20153026
[9] Thewissen, J. G. M. et al. (2007). "Whales originated from aquatic artiodactyls in the Eocene epoch of India" Nature. 450 (7173): 1190–1194
[10] Colleary, C. et al. (2015) "Chemical, experimental, and morphological evidence for diagenetically altered melanin in exceptionally preserved fossils". Proceedings of the National Academy of Sciences of the United States. 112 (41): 12592–12597
[11] Polly, David, et al. (2006) "Earliest known carnivoran auditory bulla and support for a recent origin of crown-clade carnivora (Eutheria, Mammalia)". Palaeontology. 49 (5): 1019–1027
[12] Dennis O'Neil (1999). “The First Primates”. Palomar College
[13] Feduccia, Alan (1995). "Explosive evolution in Tertiary birds and mammals". Science 267 (5198): 637–638
[14] Friedman M. (2010). “Explosive morphological diversification of spiny-finned teleost fishes in the aftermath of the end-Cretaceous extinction”. Biological sciences, 277(1688), 1675–1683
 
Hello Pierre
I just read the 6 pages of the forum on mass extinction.
Thank you very much for sharing your work.
I am not a scientist at all and your way of writing makes this subject accessible to everyone.
Thank you, really.

For information, for those who are interested, the two plants you mention are two homeopathic remedies...
Drosera is a known remedy for coughs and whooping coughs, etc.
And Aldrovanda vesiculosa has been observed in India since the 16th century.
A propos des plantes carnivores : les Drosera

Thank you also for sending me your work in pdf, in English.
I have the text in bilingual, which allows me to continue my learning of English by reading very interesting texts.

For Perlou, if she wishes, I have put all the French text in word.

Channa
 
Channa, merci pour ta proposition et bien sûr je suis intéressée, peux tu donner le lien s'il te plait... Merci beaucoup...

Channa, thank you for your proposal and of course I am interested, can you please give the link... Thanks a lot...
 
``I'm finding this information riveting and so easily absorbable. As others have said Pierre, you have the storytellers ability to make this incredible information so clear and easily understood.

My grandson, aged 9, has got an obsession with anything to do with comets. His father is very leery of letting him talk to me on this subject but we find moments to chatter nonetheless. Your illustration above on the massive growth of lifeforms around the K/T extinction will, I have no doubt, fascinate him. I don't, of course, talk about the cyclical nature of these things. Thank you for this amazing work.
 

Chapter 6: The Cambrian Life Explosion​


The Cambrian life explosion took place about 541 Mya, soon in geological terms, after a mass extinction that was probably due to cometary impacts[1]. Two substantial impact craters are coeval with this mass extinction: Acraman and Beaverhead[2]. The cometary impact hypothesis is strengthened further by the discovery of typical cometary impact markers like iridium, osmium and platinum spikes[3] at the Precambrian-Cambrian boundary.

During this exceptional life explosion almost all the present day 31 animal phyla[4] appeared quite suddenly[5]:

origin cambrian explosion bw.jpg

(c) Royal Ontario Museum
The Cambrian explosion marks the apparition of most phyla


The Cambrian animals reveal a level of complexity[6] comparable to modern animals although their morphologies differ. This evolutionary leap is all the more stunning that before the Cambrian explosion most organisms were unicellular along with a minority of few very simple multicellular organisms.

Basically, before the Cambrian there is no animal fossil and after there are incomparably complex animals like the trilobite, weighing as much as 4.5 kilograms[7], and being more than 45 centimeters[8] long, equipped with fully formed eyes, legs, digestive system and exoskeleton:


Trilobite_Ordovicien.jpg

© Alias Collection
Fossil of a Paraceraurus trilobite from the Volchow River, Russia.


After its sudden appearance, the trilobite didn’t notably evolve for 300 million year until it disappeared during the Permian–Triassic extinction 252 Mya. A close cousin[9] of the trilobite is the horseshoe crab which displays a similar exoskeleton[10] and is still alive today.

horseshoe crab.jpg

© Warren1225
Horseshoe crab, a close relative to the trilobites


An even more striking example of hundreds of millions of years of existence devoid of notable evolution is the tardigrade, also known as water bear, a microscopic but complex animal that suddenly appeared during the Cambrian[11] explosion and still found today everywhere on Earth, from mountaintops to the deep sea and from tropical rainforests to the Antarctica[12]. Tardigrades even live in erupting mud volcanoes[13].

tardigrade bw.png

© Eye of Science
Electron microscopy photograph of a tardigrade


An even more striking is the comb jelly that suddenly appeared during the Cambrian explosion. Comb jelly is still extant through its close relatives but Cambrian comb jelly had a more complex nervous system than its modern descendants[14].


comb jelly bw.jpg

© Holly Sullivan
An artist’s impression of the comb jelly fossil


The sudden appearance of the trilobites, with no ancestor whatsoever, prompted Charles Darwin to qualify it as "undoubtedly of the gravest nature"[15] He should have added “…for the credibility of me incremental random evolution theory”.

The trilobite is not an isolated case of sudden apparition. Marine animals like sea urchins and star fish also displayed a “rapid, extensive innovation”:
There is considerable biogeographic complexity to the [Cambrian] recovery. […] An exquisitely preserved echinoderm fauna from the Fammennian Hongegulung Formation of northwestern China demonstrates the rapid, extensive innovation among blastoids and crinoids.[16]

The Cambrian life explosion saw tens of thousands of new complex animal species suddenly appearing on Earth, including a wide variety of worms, mollusks, brachiopods, echinoderms, arthropods and fishes to name but a few[17].


[1] Signor, P.W. et al (1982)."Sampling bias, gradual extinction patterns and catastrophes in the fossil record". In Silver, L.T. “Geological implications of impacts of large asteroids and comets on the earth”. Geological Society of America.
[2] Keller, Gerta (2005) “Impacts, volcanism and mass extinction: Random coincidence or cause and effect?”Australian Journal of Earth Sciences 52. 10.1080.
[3] Hsu, K., et al. (1985). “‘Strangelove ocean’ before the Cambrian explosion”. Nature 316, 809–811
[4] A phylum (plural phyla) is a level of classification or taxonomic rank below kingdom and above class. As of today, there are 31 known animal phyla. For example human beings are part of the animal kingdom, the chordata phylum and the mammalian class.
[5] Maloof, A. C. et al. (2010). "The earliest Cambrian record of animals and ocean geochemical change". Geological Society of America Bulletin. 122 (11–12): 1731–1774.
[6] Whittington, H. B. (1979). “Early arthropods, their appendages and relationships”. In M. R. House, “The origin of major invertebrate groups” pp. 253–268. The Systematics Association Special Volume, 12. Academic Press
[7] 9.9 lb
[8] 18 in
[9] American Museum of Natural History Editors. (2012). “Horseshoe crabs are one of nature's great survivors”. Phys.org
[10] Lienhard, John H. (2009). “No. 2496 Trilobites”. Engines of our Ingenuity
[11] Grimaldi, David et al. (2005) “Evolution of the Insects”. Cambridge University Press. pp. 96–97
[12] Sarah Bordenstein (2021) ‘’Tardigrades (Water Bears)’’. Microbial Life - Educational Resources
[13] Suen, C. et al.(2021) “Tardigrades, Water Bears, Moss Piglets Tardigrada (Spallanzani 1777)”. EDIS, 2021(2), 2-2
[14] James Urquhart (2021) “Ancient comb jelly had more complex nerves than its modern relatives” New Scientist
[15] Darwin, C. (1859) “On the Origin of Species by Natural Selection”. Murray. pp. 202, 306–308
[16] Douglas Erwin (2001) “Lessons from the past: Biotic recoveries from mass extinctions”. PNAS 98 (10) 5399-5403
[17] Rex E. Crick Markes et al. (1999) “Cambrian faune”. Encyclopaedia Britannica
 

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