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66.0 – 0 Ma
Torre Sant'Andrea, Salento, Italy)
Name formalityFormal
Nickname(s)Age of Mammals
Usage information
Celestial body
K-Pg extinction event.
Lower boundary GSSPEl Kef Section, El Kef, Tunisia
36°09′13″N 8°38′55″E / 36.1537°N 8.6486°E / 36.1537; 8.6486
Lower GSSP ratified1991
Upper boundary definitionN/A
Upper boundary GSSPN/A
Upper GSSP ratifiedN/A

The Cenozoic (

Chicxulub impactor

The Cenozoic is also known as the Age of Mammals because the terrestrial animals that dominated both hemispheres were mammals – the eutherians (placentals) in the northern hemisphere and the metatherians (marsupials, now mainly restricted to Australia and to some extent South America) in the southern hemisphere. The extinction of many groups allowed mammals and birds to greatly diversify so that large mammals and birds dominated life on Earth. The continents also moved into their current positions during this era.

The climate during the early Cenozoic was warmer than today, particularly during the Paleocene–Eocene Thermal Maximum. However, the Eocene to Oligocene transition and the Quaternary glaciation dried and cooled Earth.


Cenozoic derives from the Greek words kainós (καινός 'new') and zōḗ (ζωή 'life').[3] The name was proposed in 1840 by the British geologist John Phillips (1800–1874), who originally spelled it Kainozoic.[4][5][6] The era is also known as the Cænozoic, Caenozoic, or Cainozoic (/ˌk.nəˈz.ɪk, ˌk-/).[7][8]

In name, the Cenozoic (lit.'new life') is comparable to the preceding Mesozoic ('middle life') and Paleozoic ('old life') Eras, as well as to the Proterozoic ('earlier life') Eon.


The Cenozoic is divided into three periods: the

better organise and group the many significant events that occurred during this comparatively short interval of time. Knowledge of this era is more detailed than any other era because of the relatively young, well-preserved rocks associated with it.


The Paleogene spans from the extinction of non-avian dinosaurs, 66 million years ago, to the dawn of the Neogene, 23.03 million years ago. It features three


creodonts (extinct carnivores, unrelated to existing Carnivora



Oligocene Epoch spans from 33.9 million to 23.03 million years ago. The Oligocene featured the expansion of grasslands which had led to many new species to evolve, including the first elephants, cats, dogs, marsupials and many other species still prevalent today. Many other species of plants evolved in this period too. A cooling period featuring seasonal rains was still in effect. Mammals still continued to grow larger and larger.[22]


The Neogene spans from 23.03 million to 2.58 million years ago. It features 2 epochs: the Miocene, and the Pliocene.[23]


seed plants families were present by the end of the Miocene.[24]




Phanerozoic Eon
. It features modern animals, and dramatic changes in the climate. It is divided into two epochs: the Pleistocene and the Holocene.



Homo sapiens. 100,000 years ago marked the end of one of the worst droughts in Africa, and led to the expansion of primitive humans. As the Pleistocene drew to a close, a major extinction wiped out much of the world's megafauna, including some of the hominid species, such as Neanderthals. All the continents were affected, but Africa to a lesser extent. It still retains many large animals, such as hippos.[27]


Sixth Extinction". It is often cited that over 322 recorded species have become extinct due to human activity since the Industrial Revolution,[29][30] but the rate may be as high as 500 vertebrate species alone, the majority of which have occurred after 1900.[31]


Southeast Asia; Antarctica moved into its current position over the South Pole; the Atlantic Ocean widened and, later in the era (2.8 million years ago), South America became attached to North America with the isthmus of Panama

India collided with Asia 55 to 45 million years ago creating the Himalayas; Arabia collided with Eurasia, closing the Tethys Ocean and creating the Zagros Mountains, around 35 million years ago.[32]

The break-up of Gondwana in



In the Cretaceous, the climate was hot and humid with lush forests at the poles, there was no permanent ice and sea levels were around 300 metres higher than today. This continued for the first 10 million years of the Paleocene, culminating in the Paleocene–Eocene Thermal Maximum about 55.5 million years ago. Around 50 million years ago Earth entered a period of long term cooling. This was mainly due to the collision of India with Eurasia, which caused the rise of the Himalayas: the upraised rocks eroded and reacted with CO2 in the air, causing a long-term reduction in the proportion of this greenhouse gas in the atmosphere. Around 35 million years ago permanent ice began to build up on Antarctica.[34] The cooling trend continued in the Miocene, with relatively short warmer periods. When South America became attached to North America creating the Isthmus of Panama around 2.8 million years ago, the Arctic region cooled due to the strengthening of the Humboldt and Gulf Stream currents,[35] eventually leading to the glaciations of the Quaternary ice age, the current interglacial of which is the Holocene Epoch. Recent analysis of the geomagnetic reversal frequency, oxygen isotope record, and tectonic plate subduction rate, which are indicators of the changes in the heat flux at the core mantle boundary, climate and plate tectonic activity, shows that all these changes indicate similar rhythms on million years' timescale in the Cenozoic Era occurring with the common fundamental periodicity of ~13 Myr during most of the time.[36] The levels of carbonate ions in the ocean fell over the course of the Cenozoic.[37]


Early in the Cenozoic, following the

terror birds", and were formidable predators. Mammals came to occupy almost every available niche (both marine and terrestrial), and some also grew very large, attaining sizes not seen in most of today's terrestrial mammals. The ranges of many Cenozoic bird clades were governed by latitude and temperature and have contracted over the course of this era as the world cooled.[38]

During the Cenozoic,

colubrids, following the evolution of their current primary prey source, the rodents

In the earlier part of the Cenozoic, the world was dominated by the

. But as the forests began to recede and the climate began to cool, other mammals took over.

The Cenozoic is full of mammals both strange and familiar, including

brontotheres, various bizarre groups of mammals from South America, such as the vaguely elephant-like pyrotheres and the dog-like marsupial relatives called borhyaenids and the monotremes and marsupials of Australia. Mammal evolution in the Cenozoic was predominantly shaped by climatic and geological processes.[40]

Cenozoic calcareous nannoplankton experienced rapid rates of speciation and reduced species longevity, while suffering prolonged declines in diversity during the Eocene and Neogene. Diatoms, in contrast, experienced major diversification over the Eocene, especially at high latitudes, as the world's oceans cooled.[41] Diatom diversification was particularly concentrated at the Eocene-Oligocene boundary. A second major pulse of diatom diversification occurred over the course of the Middle and Late Miocene.[42]

See also


  1. ^ "Cenozoic". Lexico UK English Dictionary. Oxford University Press. Archived from the original on 23 November 2021.
  2. ^ "Cenozoic". Merriam-Webster.com Dictionary.
  3. ^ "Cenozoic". Online Etymology Dictionary.
  4. ^ Phillips, John (1840). "Palæozoic series". Penny Cyclopaedia of the Society for the Diffusion of Useful Knowledge. Vol. 17. London, England: Charles Knight and Co. pp. 153–154. From pp. 153–154: "As many systems or combinations of organic forms as are clearly traceable in the stratified crust of the globe, so many corresponding terms (as Palæozoic, Mesozoic, Kainozoic, &c.) may be made, ... "
  5. ^ Wilmarth, Mary Grace (1925). Bulletin 769: The Geologic Time Classification of the United States Geological Survey Compared With Other Classifications, accompanied by the original definitions of era, period and epoch terms. Washington, D.C., U.S.: U.S. Government Printing Office. p. 8.
  6. ^ The evolution of the spelling of "Cenozoic" is reviewed in:
    • Harland, W. Brian; Armstrong, Richard L.; Cox, Allen V.; Craig, Lorraine E.; Smith, David G.; Smith, Alan G. (1990). "The Chronostratic Scale". A Geologic Time Scale 1989. Cambridge, England, U.K.: Cambridge University Press. p. 31. .
    Although John Phillips originally spelled it as "Kainozoic" in 1840, he spelled it "Cainozoic" a year later:
  7. ^ "Cainozoic". Dictionary.com Unabridged (Online). n.d.
  8. ^ "Cainozoic". Oxford English Dictionary (2nd ed.). 1989.
  9. .
  10. .
  11. .
  12. .
  13. ^ Royal Tyrrell Museum (28 March 2012), Lamniform sharks: 110 million years of ocean supremacy, archived from the original on 7 August 2013, retrieved 12 July 2017
  14. S2CID 205248384
    . Retrieved 19 January 2023.
  15. ^ University of California. "Eocene Climate". University of California.
  16. ^ National Geographic Society (24 January 2017). "Eocene". National Geographic. Archived from the original on 8 May 2010.
  17. . Retrieved 16 April 2023.
  18. . Retrieved 16 April 2023.
  19. .
  20. . Retrieved 4 August 2023.
  21. . Retrieved 28 July 2023.
  22. ^ University of California. "Oligocene". University of California.
  23. ^ "Neogene". Encyclopædia Britannica.
  24. ^ University of California. "Miocene". University of California.
  25. ^ University of California. "Pliocene". University of California.
  26. ^ Adams, Jonathan. "Pliocene climate". Oak Ridge National Library. Archived from the original on 25 February 2015.
  27. ^ University of California. "Pleistocene". University of California. Archived from the original on 24 August 2014. Retrieved 25 April 2015.
  28. ^ University of California. "Holocene". University of California.
  29. ^ "Sixth Extinction extinctions". Scientific American.
  30. ^ IUCN (3 November 2009). "Sixth Extinction". IUCN.
  31. PMID 26601195.{{cite journal}}: CS1 maint: numeric names: authors list (link
  32. .
  33. .
  34. .
  35. ^ "How the Isthmus of Panama Put Ice in the Arctic". Oceanus Magazine.
  36. .
  37. . Retrieved 26 December 2023 – via Elsevier Science Direct.
  38. .
  39. ^ "The Cenozoic Era". ucmp.berkeley.edu.
  40. PMID 36442115
  41. . Retrieved 8 January 2024 – via GeoScienceWorld.
  42. . Retrieved 8 March 2024.

Further reading

External links