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Timeline of the evolutionary history of life

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For the history of evolutionary biology, see History of evolutionary thought.
This article is about the timeline of evolution in a general aspect. See also the timeline of human evolution.

This timeline of the evolution of life outlines the major events in the development of life on the planet Earth (See Organism). For a thorough explanatory context, see the history of Earth, and geologic time scale. The dates given in this article are estimates based on scientific evidence.

In biology, evolution is the process by which populations of organisms acquire and pass on novel traits from generation to generation. Its occurrence over large stretches of time explains the origin of new species and ultimately the vast diversity of the biological world. Contemporary species are related to each other through common descent, products of evolution and speciation over billions of years.

Basic timeline

The basic timeline is a 4.5 billion year old Earth, with (very approximate) dates:

Detailed timeline

Ma, ("megaannum") means "million years ago". ka means "thousand years ago" and ya means "years ago"

Hadean Eon

3800 Ma and earlier.

Date Event
4600 Ma The planet Earth forms from the accretion disc revolving around the young Sun.
4500 Ma According to the giant impact hypothesis the moon is formed when the planet Earth and the planet Theia collide, sending a very large number of moonlets into orbit around the young Earth which eventually coalesce to form the Moon.[1] The gravitational pull of the new Moon stabilises the Earth's fluctuating axis of rotation and sets up the conditions in which life formed.[2]
4100 Ma The surface of the Earth cools enough for the crust to solidify. The atmosphere and the oceans form.[3] PAH infall,[4] and iron sulfide synthesis along deep ocean platelet boundaries, may have led to the RNA world of competing organic compounds.
Between 4500 and 3500 Ma The earliest life appears, possibly derived from self-reproducing RNA molecules.[5][6] The replication of these organisms requires resources like energy, space, and smaller building blocks, which soon become limited, resulting in competition, with natural selection favouring those molecules which are more efficient at replication. DNA molecules then take over as the main replicators and these archaic genomes soon develop inside enclosing membranes which provide a stable physical and chemical environment conducive to their replication: proto-cells.[7][8][9]
3900 Ma Late Heavy Bombardment: peak rate of impact events upon the inner planets by meteoroids. This constant disturbance may have obliterated any life that had evolved to that point, or possibly not, as some early microbes could have survived in hydrothermal vents below the Earth's surface;[10] or life might have been transported to Earth by a meteoroid.[11]
Somewhere between 3900 and 2500 Ma Cells resembling prokaryotes appear.[12] These first organisms are chemoautotrophs: they use carbon dioxide as a carbon source and oxidize inorganic materials to extract energy. Later, prokaryotes evolve glycolysis, a set of chemical reactions that free the energy of organic molecules such as glucose and store it in the chemical bonds of ATP. Glycolysis (and ATP) continue to be used in almost all organisms, unchanged, to this day.[13][14]

Archean Eon

3800 Ma – 2500 Ma

Date Event
3500 Ma Lifetime of the last universal ancestor;[15][16] the split between bacteria and archaea occurs.[17]

Bacteria develop primitive forms of photosynthesis which at first do not produce oxygen.[18] These organisms generate ATP by exploiting a proton gradient, a mechanism still used in virtually all organisms.

3000 Ma Photosynthesizing cyanobacteria evolve; they use water as a reducing agent, thereby producing oxygen as waste product.[19] More recent research[citation needed], however, suggests a later time of 2700 Ma. The oxygen initially oxidizes dissolved iron in the oceans, creating iron ore. The oxygen concentration in the atmosphere slowly rises, acting as a poison for many bacteria. The Moon is still very close to Earth and causes tides 1,000 feet (305 m) high. The Earth is continually wracked by hurricane-force winds. These extreme mixing influences are thought to stimulate evolutionary processes. (See Oxygen catastrophe)
2700 Ma Timeframe of cyanobacteria evolution suggested by more recent research.

Proterozoic Eon

2500 Ma – 542 Ma

Date Event
2400 Ma Earliest cyanobacteria
2000 Ma First acritarchs
By 1850 Ma Eukaryotic cells appear[20][21]
1500 Ma First structurally complex eukaryotes
1400 Ma Great increase in stromatolite diversity Eukaryotes contain membrane-bound organelles with diverse functions, probably derived from prokaryotes engulfing each other via phagocytosis. (See Endosymbiosis)
By 1200 Ma Sexual reproduction first appears, increasing the rate of evolution.[22]
1200 Ma Simple multicellular organisms evolve, mostly consisting of cell colonies of limited complexity. First multicellular red algae evolve
1100 Ma Earliest dinoflagellates
1000 Ma First vaucherian algae (ex: Palaeovaucheria)
750 Ma First protozoa (ex: Melanocyrillium)
850–630 Ma A global glaciation may have occurred.[23][24] Opinion is divided on whether it increased or decreased biodiversity or the rate of evolution.[25][26][27]
580–542 Ma The Ediacaran biota represent the first large, complex multicellular organisms - although their affinities remain a subject of debate.[28]
580–500 Ma Most modern phyla of animals begin to appear in the fossil record during the Cambrian explosion.[29][30]
580–540 Ma The accumulation of atmospheric oxygen allows the formation of an ozone layer.[31] This blocks ultraviolet radiation, permitting the colonisation of the land.[31]
560 Ma Earliest fungi
550 Ma First fossil evidence for ctenophora (comb-jellies), porifera (sponges), and anthozoa (corals & anemones)

Phanerozoic Eon

542 Ma – present

The Phanerozoic Eon, literally the "period of well-displayed life", marks the appearance in the fossil record of abundant, shell-forming and/or trace-making organisms. It is subdivided into three eras, the Paleozoic, Mesozoic and Cenozoic, which are divided by major mass extinctions.

Paleozoic Era

542 Ma – 251.0 Ma

Date Event
535 Ma Major diversification of living things in the oceans: chordates, arthropods (e.g. trilobites, crustaceans), echinoderms, mollusks, brachiopods, foraminifers and radiolarians, etc.
530 Ma The first known footprints on land date to 530 Ma, indicating that early animal explorations may have predated the development of terrestrial plants.[32]
525 Ma Earliest graptolites.
510 Ma First cephalopods (Nautiloids) and chitons.
505 Ma Fossilization of the Burgess Shale.
485 Ma First vertebrates with true bones (jawless fishes).
450 Ma Land arthropod burrows (millipedes) appear, along with the first complete conodonts and echinoids.
440 Ma First agnathan fishes: Heterostraci, Galeaspida, and Pituriaspida.
434 Ma The first primitive plants move onto land,[33] having evolved from green algae living along the edges of lakes.[34] They are accompanied by fungi[citation needed], which may have aided the colonization of land through symbiosis.
420 Ma Earliest ray-finned fishes, trigonotarbid arachnids, and land scorpions.
410 Ma First signs of teeth in fish. Earliest nautiid nautiloids, lycophytes, and trimerophytes.
395 Ma First lichens, stoneworts. Earliest harvestman, mites, hexapods (springtails) and ammonoids. The first known tetrapod tracks on land.
363 Ma By the start of the Carboniferous Period, the Earth begins to be recognisable. Insects roamed the land and would soon take to the skies; sharks swam the oceans as top predators,[35] and vegetation covered the land, with seed-bearing plants and forests soon to flourish.

Four-limbed tetrapods gradually gain adaptations which will help them occupy a terrestrial life-habit.

360 Ma First crabs and ferns. Land flora dominated by seed ferns.
350 Ma First large sharks, ratfishes, and hagfish.
340 Ma Diversification of amphibians.
330 Ma First amniote vertebrates (Paleothyris).
320 Ma Synapsids separate from sauropsids (reptiles) in late Carboniferous.[36]
305 Ma Earliest diapsid reptiles (e.g. Petrolacosaurus).
280 Ma Earliest beetles, seed plants and conifers diversify while lepidodendrids and sphenopsids decrease. Terrestrial temnospondyl amphibians and pelycosaurs (e.g. Dimetrodon) diversify in species.
275 Ma Therapsids separate from synapsids.
251.4 Ma The Permian-Triassic extinction event eliminates over 90-95% of marine species. Terrestrial organisms were not as seriously affected as the marine biota. This "clearing of the slate" may have led to an ensuing diversification, but life on land took 30M years to completely recover.[37]

Mesozoic Era

Date Event
From 251.4 Ma The Mesozoic Marine Revolution begins: increasingly well-adapted and diverse predators pressurise sessile marine groups; the "balance of power" in the oceans shifts dramatically as some groups of prey adapt more rapidly and effectively than others.
245 Ma Earliest ichthyosaurs.
240 Ma Increase in diversity of gomphodont cynodonts and rhynchosaurs.
225 Ma Earliest dinosaurs (prosauropods), first cardiid bivalves, diversity in cycads, bennettitaleans, and conifers. First teleost fishes.
220 Ma
Eoraptor, among the earliest dinosaurs, appeared in the fossil record 230 million years ago.

Gymnosperm forests dominate the land; herbivores grow to huge sizes in order to accommodate the large guts necessary to digest the nutrient-poor plants.[citation needed], first flies and turtles (Odontochelys). First Coelophysoid dinosaurs

215 Ma First mammals (e.g. Eozostrodon), minor vertebrate extinctions occur
200 Ma The first accepted evidence for viruses (at least, the group Geminiviridae) exists.[38] Viruses are still poorly understood and may have arisen before "life" itself, or may be a more recent phenomenon.

Major extinctions in terrestrial vertebrates and large amphibians. Earliest examples of Ankylosaurian dinosaurs

195 Ma First pterosaurs with specialized feeding (Dorygnathus). First sauropod dinosaurs. Diversification in small, ornithischian dinosaurs: heterodontosaurids, fabrosaurids, and scelidosaurids.
190 Ma Pliosaurs appear in the fossil record. First lepidopteran insects (Archaeolepis), hermit crabs, modern starfish, irregular echinoids, corbulid bivalves, and tubulipore bryozoans. Extensive development of sponge reefs.
176 Ma First members of the Stegosauria group of dinosaurs
170 Ma Earliest salamanders, newts, cryptoclidid & elasmosaurid plesiosaurs, and cladotherian mammals. Cynodonts become extinct while sauropod dinosaurs diversify.
165 Ma First rays and glycymeridid bivalves.
161 Ma Ceratopsian dinosaurs appear in the fossil record (Yinlong)
155 Ma First blood-sucking insects (ceratopogonids), rudist bivalves, and cheilosome bryozoans. Archaeopteryx, a possible ancestor to the birds, appears in the fossil record, along with triconodontid and symmetrodont mammals. Diversity in stegosaurian and theropod dinosaurs.
130 Ma The rise of the Angiosperms: These flowering plants boast structures that attract insects and other animals to spread pollen. This innovation causes a major burst of animal evolution through co-evolution. First freshwater pelomedusid turtles.
120 Ma Oldest fossils of heterokonts, including both marine diatoms and silicoflagellates.
115 Ma First monotreme mammals.
110 Ma First hesperornithes, toothed diving birds. Earliest limopsid, verticordiid, and thyasirid bivalves.
106 Ma Spinosaurus, the largest theropod dinosaur, appears in the fossil record.
100 Ma Earliest bees.
90 Ma Extinction of ichthyosaurs. Earliest snakes and nuculanid bivalves. Large diversification in angiosperms: magnoliids, rosids, hamamelidids, monocots, and ginger. Earliest examples of ticks.
80 Ma First ants.
70 Ma Multituberculate mammals increase in diversity. First yoldiid bivalves.
68 Ma Tyrannosaurus, the largest terrestrial predator of North America appears in the fossil record. First species of Triceratops.

Cenozoic Era

65.5 Ma – present

Date Event
65.5 Ma The Cretaceous–Tertiary extinction event eradicates about half of all animal species, including mosasaurs, pterosaurs, plesiosaurs, ammonites, belemnites, rudist and inoceramid bivalves, most planktic foraminifers, and all of the dinosaurs excluding their descendants the birds [39]
From 65 Ma Rapid dominance of conifers and ginkgos in high latitudes, along with mammals becoming the dominant species. First psammobiid bivalves. Rapid diversification in ants.
63 Ma Evolution of the creodonts, an important group of carnivorous mammals.
60 Ma Diversification of large, flightless birds. Earliest true primates, along with the first semelid bivalves, edentates, carnivorous and lipotyphlan mammals, and owls. The ancestors of the carnivorous mammals (miacids) were alive.
56 Ma Gastornis, a large, flightless bird appears in the fossil record, becoming an apex predator at the time.
55 Ma Modern bird groups diversify (first song birds, parrots, loons, swifts, woodpeckers), first whale (Himalayacetus), earliest rodents, lagomorphs, armadillos, appearance of sirenians, proboscideans, perissodactyl and artiodactyl mammals in the fossil record. Angiosperms diversify. The ancestor (according to theory) of the species in Carcharodon, the early mako shark Isurus hastalis, is alive.
52 Ma First bats appear (Onychonycteris).
50 Ma Peak diversity of dinoflagellates and nanofossils, increase in diversity of anomalodesmatan and heteroconch bivalves, brontotheres, tapirs, rhinoceroses, and camels appear in the fossil record, diversification of primates.
40 Ma Modern-type butterflies and moths appear. Extinction of Gastornis. Basilosaurus, one of the first of the giant whales, appeared in the fossil record.
37 Ma First Nimravid carnivores ("False Saber-toothed Cats") - these species are unrelated to modern-type felines
35 Ma Grasses evolve from among the angiosperms; grasslands begin to expand. Slight increase in diversity of cold-tolerant ostracods and foraminifers, along with major extinctions of gastropods, reptiles, and amphibians. Many modern mammal groups begin to appear: first glyptodonts, ground sloths, dogs, peccaries, and the first eagles and hawks. Diversity in toothed and baleen whales.
33 Ma Evolution of the thylacinid marsupials (Badjcinus).
30 Ma First balanids and eucalypts, extinction of embrithopod and brontothere mammals, earliest pigs and cats.
28 Ma Paraceratherium appears in the fossil record, the largest terrestrial mammal that ever lived.
25 Ma First deer.
20 Ma First giraffes and giant anteaters, increase in bird diversity.
15 Ma Mammut appears in the fossil record, first bovids and kangaroos, diversity in Australian megafauna.
10 Ma Grasslands and savannas are established, diversity in insects, especially ants and termites, horses increase in body size and develop high-crowned teeth, major diversification in grassland mammals and snakes.
6.5 Ma First hominin (Sahelanthropus).
6 Ma Australopithecines diversify (Orrorin, Ardipithecus)
5 Ma First tree sloths and hippopotami, diversification of grazing herbivores, large carnivorous mammals, burrowing rodents, kangaroos, birds, and small carnivores, vultures increase in size, decrease in the number of perissodactyl mammals. Extinction of Nimravid carnivores
4.8 Ma Mammoths appear in the fossil record.
4 Ma Evolution of Australopithecus, Stupendemys appears in the fossil record as the largest freshwater turtle.
3 Ma The Great American Interchange, where various land and freshwater faunas migrated between North and South America. Armadillos, opossums, hummingbirds, and vampire bats traveled to North America while horses, tapirs, saber-toothed cats, and deer entered South America. The first short-faced bears (Arctodus) appear.
2.7 Ma Evolution of Paranthropus
2.5 Ma The earliest species of Smilodon evolve
2 Ma First members of the genus Homo appear in the fossil record. Diversification of conifers in high latitudes. The eventual ancestor of cattle, Bos primigenius evolves in India
1.7 Ma Extinction of australopithecines.
1.2 Ma Evolution of Homo antecessor. The last members of Paranthropus die out.
600 ka Evolution of Homo heidelbergensis
350 ka Evolution of Neanderthals
300 ka Gigantopithecus, a giant relative of the orangutan dies out from Asia
200 ka Anatomically modern humans appear in Africa.[40][41][42] Around 50,000 years before present they start colonising the other continents, replacing the Neanderthals in Europe and other hominins in Asia.
40 ka The last of the giant monitor lizards (Megalania) die out
30 ka Extinction of Neanderthals
15 ka The last Woolly rhinoceros (Coelodonta) are believed to have gone extinct
11 ka The giant short-faced bears (Arctodus) vanish from North America, with the last Giant Ground Sloths dying out. All Equidae become extinct in North America
10 ka The Holocene Epoch starts 10,000[43] years ago after the Late Glacial Maximum. The last mainland species of Woolly mammoth (Mammuthus primigenius) die out, as does the last Smilodon species
6 ka Small populations of American Mastodon die off in places like Utah and Michigan
4500 ya The last members of a dwarf race of Woolly Mammoths vanish from Wrangel Island near Alaska
397 ya (1627) The last recorded wild Aurochs die out
88 ya (1936) The Thylacine goes extinct in a Tasmanian zoo, the last member of the family Thylacinidae

See also

Template:Wikipedia-Books

Further reading

References

  1. ^ Planetary Science Institute page on the Giant Impact Hypothesis. Hartmann and Davis belonged to the PSI. This page also contains several paintings of the impact by Hartmann himself.
  2. ^ "Because the Moon helps stabilize the tilt of the Earth's rotation, it prevents the Earth from wobbling between climatic extremes. Without the Moon, seasonal shifts would likely outpace even the most adaptable forms of life." Making the Moon Astrobiology Magazine. (URL accessed on August 7, 2010)
  3. ^ "However, once the Earth cooled sufficiently, sometime in the first 700 million years of its existence, clouds began to form in the atmosphere, and the Earth entered a new phase of development." How the Oceans Formed (URL accessed on January 9, 2005)
  4. ^ *The 'PAH World'
  5. ^ Gilbert, Walter (1986). "The RNA World". Nature. 319 (6055): 618. Bibcode:1986Natur.319..618G. doi:10.1038/319618a0. {{cite journal}}: Unknown parameter |month= ignored (help)
  6. ^ Joyce, G.F. (2002). "The antiquity of RNA-based evolution". Nature. 418 (6894): 214–21. doi:10.1038/418214a. PMID 12110897.
  7. ^ Hoenigsberg, H. (December 2003). "Evolution without speciation but with selection: LUCA, the Last Universal Common Ancestor in Gilbert's RNA world". Genetic and Molecular Research. 2 (4): 366–375. PMID 15011140. Retrieved 2008-08-30.(also available as PDF)
  8. ^ Trevors, J. T. and Abel, D. L. (2004). "Chance and necessity do not explain the origin of life". Cell Biol. Int. 28 (11): 729–39. doi:10.1016/j.cellbi.2004.06.006. PMID 15563395.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  9. ^ Forterre, P., Benachenhou-Lahfa, N., Confalonieri, F., Duguet, M., Elie, C. and Labedan, B. (1992). "The nature of the last universal ancestor and the root of the tree of life, still open questions". BioSystems. 28 (1–3): 15–32. doi:10.1016/0303-2647(92)90004-I. PMID 1337989.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  10. ^ Steenhuysen, Julie (May 21, 2009). "Study turns back clock on origins of life on Earth". Reuters.com. Reuters. Retrieved May 21, 2009.
  11. ^ " Between about 3.8 billion and 4.5 billion years ago, no place in the solar system was safe from the huge arsenal of asteroids and comets left over from the formation of the planets. Sleep and Zahnle calculate that Earth was probably hit repeatedly by objects up to 500 kilometers across" Geophysicist Sleep: Martian underground may have harbored early life (URL accessed on January 9, 2005)
  12. ^ Carl Woese, J Peter Gogarten, "When did eukaryotic cells (cells with nuclei and other internal organelles) first evolve? What do we know about how they evolved from earlier life-forms?" Scientific American, October 21, 1999.
  13. ^ Romano, AH; Conway, T. (1996). "Evolution of carbohydrate metabolic pathways". Res Microbiol. 147 (6–7): 448–55. doi:10.1016/0923-2508(96)83998-2. PMID 9084754. {{cite journal}}: Cite has empty unknown parameter: |author-name-separator= (help); Unknown parameter |author-separator= ignored (help)
  14. ^ Knowles JR (1980). "Enzyme-catalyzed phosphoryl transfer reactions". Annu. Rev. Biochem. 49 (1): 877–919. doi:10.1146/annurev.bi.49.070180.004305. PMID 6250450.
  15. ^ Doolittle, W. Ford (February, 2000). Uprooting the tree of life. Scientific American 282 (6): 90–95.
  16. ^ Nicolas Glansdorff, Ying Xu & Bernard Labedan: The Last Universal Common Ancestor : emergence, constitution and genetic legacy of an elusive forerunner. Biology Direct 2008, 3:29.
  17. ^ Hahn, Jürgen (1986). "Traces of Archaebacteria in ancient sediments". System Applied Microbiology. 7 (Archaebacteria '85 Proceedings): 178–83. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  18. ^ Olson JM (2006). "Photosynthesis in the Archean era". Photosyn. Res. 88 (2): 109–17. doi:10.1007/s11120-006-9040-5. PMID 16453059. {{cite journal}}: Unknown parameter |month= ignored (help)
  19. ^ Buick R (2008). "When did oxygenic photosynthesis evolve?". Philos. Trans. R. Soc. Lond., B, Biol. Sci. 363 (1504): 2731–43. doi:10.1098/rstb.2008.0041. PMC 2606769. PMID 18468984. {{cite journal}}: Unknown parameter |month= ignored (help)
  20. ^ Knoll, Andrew H. (2006). "Eukaryotic organisms in Proterozoic oceans". Philosophical Transactions of the Royal Society of London, Part B. 361 (1470): 1023–38. doi:10.1098/rstb.2006.1843. PMC 1578724. PMID 16754612. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  21. ^ Fedonkin, M. A. (2003). "The origin of the Metazoa in the light of the Proterozoic fossil record" (PDF). Paleontological Research. 7 (1): 9–41. doi:10.2517/prpsj.7.9. Retrieved 2008-09-02. {{cite journal}}: Unknown parameter |month= ignored (help)
  22. ^ Nicholas J. Butterfield, "Bangiomorpha pubescens n. gen., n. sp.: implications for the evolution of sex, multicellularity, and the Mesoproterozoic/Neoproterozoic radiation of eukaryotes"
  23. ^ Hoffman, P.F. (1998-08-28). "A Neoproterozoic Snowball Earth". Science. 281 (5381): 1342–6. Bibcode:1998Sci...281.1342H. doi:10.1126/science.281.5381.1342. PMID 9721097. Retrieved 2007-05-04. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help) Full online article (pdf 260 Kb)
  24. ^ Kirschvink, J.L. (1992). "Late Proterozoic low-latitude global glaciation: The snowball Earth". In Schopf, JW, and Klein, C. (ed.). The Proterozoic Biosphere: A Multidisciplinary Study (PDF). Cambridge University Press, Cambridge. pp. 51–52.{{cite book}}: CS1 maint: multiple names: editors list (link)
  25. ^ http://researchpages.net/media/resources/2007/06/21/richtimhywelfinal.pdf
  26. ^ Corsetti, F.A. (2003-04-15). "A complex microbiota from snowball Earth times: Microfossils from the Neoproterozoic Kingston Peak Formation, Death Valley, USA". Proceedings of the National Academy of Sciences. 100 (8): 4399–4404. doi:10.1073/pnas.0730560100. PMC 153566. PMID 12682298. Retrieved 2007-06-28. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  27. ^ Corsetti, F.A. (2006). "The biotic response to Neoproterozoic Snowball Earth". Palaeogeography, Palaeoclimatology, Palaeoecology. 232 (232): 114–130. doi:10.1016/j.palaeo.2005.10.030. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  28. ^ Narbonne, Guy (2006). "The Origin and Early Evolution of Animals". Department of Geological Sciences and Geological Engineering, Queen's University. Retrieved 2007-03-10. {{cite web}}: Unknown parameter |month= ignored (help)
  29. ^ The Cambrian Period
  30. ^ The Cambrian Explosion – Timing
  31. ^ a b Formation of the Ozone Layer
  32. ^ "The oldest fossils of footprints ever found on land hint that animals may have beaten plants out of the primordial seas. Lobster-sized, centipede-like or slug like animals such as Protichnites and Climactichnites made the prints wading out of the ocean and scuttling over sand dunes about 530 million years ago. Previous fossils indicated that animals didn't take this step until 40 million years later." Oldest fossil footprints on land
  33. ^ "The oldest fossils reveal evolution of non-vascular plants by the middle to late Ordovician Period (~450–440 Ma) on the basis of fossil spores" Transition of plants to land
  34. ^ "The land plants evolved from the algae, more specifically green algae, as suggested by certain common biochemical traits" The first land plants
  35. ^ "The ancestry of sharks dates back more than 200 million years before the earliest known dinosaur. Introduction to shark evolution, geologic time and age determination
  36. ^ "Amniota - Palaeos".
  37. ^ Sahney, S. and Benton, M.J. (2008). "Recovery from the most profound mass extinction of all time" (PDF). Proceedings of the Royal Society: Biological. 275 (1636): 759–65. doi:10.1098/rspb.2007.1370. PMC 2596898. PMID 18198148.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  38. ^ "Viruses of nearly all the major classes of organisms—animals, plants, fungi and bacteria/archaea—probably evolved with their hosts in the seas, given that most of the evolution of life on this planet has occurred there. This means that viruses also probably emerged from the waters with their different hosts, during the successive waves of colonisation of the terrestrial environment." Origins of Viruses (URL accessed on January 9, 2005)
  39. ^ Chiappe, Luis M., & Dyke, Gareth J. (2002). "The Mesozoic Radiation of Birds". Annual Review of Ecology & Systematics. 33 (1): 91–124. doi:10.1146/annurev.ecolsys.33.010802.150517.{{cite journal}}: CS1 maint: multiple names: authors list (link)
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  43. ^ "International Stratigraphic Chart" (PDF). International Commission on Stratigraphy. Retrieved 2009-02-03. [dead link]

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