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The Cenozoic
Cenozoic
Era ( /ˌsiːnəˈzoʊɪk, ˌsɛ-/)[1][2] is the current geological era, covering the period from 66 million years ago to the present day. The Cenozoic
Cenozoic
is also known as the Age of Mammals, because of the large mammals that dominate it. The continents also moved into their current positions during this era.

Contents

1 Nomenclature 2 Divisions

2.1 Paleogene Period 2.2 Neogene 2.3 Quaternary

3 Animal life 4 Tectonics 5 Climate 6 Life 7 See also 8 References 9 Bibliography 10 External links

Nomenclature[edit] Cenozoic, meaning "new life," is derived from Greek καινός kainós "new," and ζωή zōḗ "life."[3] The era is also known as the Cænozoic, Caenozoic, or Cainozoic. /ˌkaɪnəˈzoʊɪk, ˌkeɪ-/;[4][5] Divisions[edit] The Cenozoic
Cenozoic
is divided into three periods: the Paleogene, Neogene, and Quaternary; and seven epochs: the Paleocene, Eocene, Oligocene, Miocene, Pliocene, Pleistocene, and Holocene. The Quaternary
Quaternary
Period was officially recognized by the International Commission on Stratigraphy in June 2009,[6] and the former term, Tertiary Period, became officially disused in 2004 due to the need to divide the Cenozoic
Cenozoic
into periods more like those of the earlier Paleozoic
Paleozoic
and Mesozoic
Mesozoic
eras.[7][why?] The common use of epochs during the Cenozoic helps paleontologists better organize and group the many significant events that occurred during this comparatively short interval of time. Knowledge of this era is relatively more detailed than any other era because of the relatively young, well-preserved rocks associated with it. Paleogene Period[edit] 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 epochs: the Paleocene, Eocene
Eocene
and Oligocene.

Basilosaurus

The Paleocene
Paleocene
epoch lasted from 66 million to 56 million years ago. Modern placental mammals originated during this time. The Paleocene
Paleocene
is a transitional point between the devastation that is the K-T extinction, to the rich jungle environment that is the Early Eocene. The Early Paleocene
Paleocene
saw the recovery of the earth. The continents began to take their modern shape, but all the continents and the subcontinent of India were separated from each other. Afro-Eurasia
Afro-Eurasia
was separated by the Tethys Sea, and the Americas were separated by the strait of Panama, as the isthmus had not yet formed. This epoch featured a general warming trend, with jungles eventually reaching the poles. The oceans were dominated by sharks[8] as the large reptiles that had once predominated were extinct. Archaic mammals filled the world such as creodonts (extinct carnivores, unrelated to existing Carnivora). The Eocene
Eocene
Epoch ranged from 56 million years to 33.9 million years ago. In the Early-Eocene, species living in dense forest were unable to evolve into larger forms, as in the Paleocene. There was nothing over the weight of 10 kilograms.[9] Among them were early primates, whales and horses along with many other early forms of mammals. At the top of the food chains were huge birds, such as Paracrax. The temperature was 30 degrees Celsius with little temperature gradient from pole to pole. In the Mid-Eocene, the Circumpolar-Antarctic current between Australia and Antarctica
Antarctica
formed. This disrupted ocean currents worldwide and as a result caused a global cooling effect, shrinking the jungles. This allowed mammals to grow to mammoth proportions, such as whales which, by that time, had become almost fully aquatic. Mammals like Andrewsarchus
Andrewsarchus
were at the top of the food-chain. The Late Eocene
Eocene
saw the rebirth of seasons, which caused the expansion of savanna-like areas, along with the evolution of grass.[10][11] The end of the Eocene
Eocene
was marked by the Eocene- Oligocene
Oligocene
extinction event, the European face of which is known as the Grande Coupure. The Oligocene
Oligocene
Epoch spans from 33.9 million to 23.03 million years ago. The Oligocene
Oligocene
featured the expansion of grass 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.[12] Neogene[edit]

Animals of the Miocene
Miocene
(Chalicotherium, Hyenadon, Entelodont...). Mammals are the dominant terrestrial vertebrates of the Cenozoic.

The Neogene
Neogene
spans from 23.03 million to 2.58 million years ago. It features 2 epochs: the Miocene, and the Pliocene.[13] The Miocene
Miocene
epoch spans from 23.03 to 5.333 million years ago and is a period in which grass spread further, dominating a large portion of the world, at the expense of forests. Kelp
Kelp
forests evolved, encouraging the evolution of new species, such as sea otters. During this time, perissodactyla thrived, and evolved into many different varieties. Apes
Apes
evolved into 30 species. The Tethys Sea
Tethys Sea
finally closed with the creation of the Arabian Peninsula, leaving only remnants as the Black, Red, Mediterranean and Caspian Seas. This increased aridity. Many new plants evolved: 95% of modern seed plants evolved in the mid-Miocene.[14] The Pliocene
Pliocene
epoch lasted from 5.333 to 2.58 million years ago. The Pliocene
Pliocene
featured dramatic climactic changes, which ultimately led to modern species and plants. The Mediterranean Sea
Mediterranean Sea
dried up for several million years (because the ice ages reduced sea levels, disconnecting the Atlantic from the Mediterranean, and evaporation rates exceeded inflow from rivers). Australopithecus
Australopithecus
evolved in Africa, beginning the human branch. The isthmus of Panama formed, and animals migrated between North and South America, wreaking havoc on local ecologies. Climatic changes brought: savannas that are still continuing to spread across the world; Indian monsoons; deserts in central Asia; and the beginnings of the Sahara
Sahara
desert. The world map has not changed much since, save for changes brought about by the glaciations of the Quaternary, such as the Great Lakes, Hudson Bay, and the Baltic sea.[15][16] Quaternary[edit] The Quaternary
Quaternary
spans from 2.58 million years ago to present day, and is the shortest geological period in the Phanerozoic
Phanerozoic
Eon. It features modern animals, and dramatic changes in the climate. It is divided into two epochs: the Pleistocene
Pleistocene
and the Holocene.

Megafauna of the Pleistocene
Pleistocene
(mammoths, cave lions, woolly rhino, Megaloceros, horses)

The Pleistocene
Pleistocene
lasted from 2.58 million to 11,700 years ago. This epoch was marked by ice ages as a result of the cooling trend that started in the Mid-Eocene. There were at least four separate glaciation periods marked by the advance of ice caps as far south as 40 degrees N latitude in mountainous areas. Meanwhile, Africa experienced a trend of desiccation which resulted in the creation of the Sahara, Namib, and Kalahari deserts. Many animals evolved including mammoths, giant ground sloths, dire wolves, saber-toothed cats, and most famously 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
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
Africa
to a lesser extent. It still retains many large animals, such as hippos.[17] The Holocene
Holocene
began 11,700 years ago and lasts to the present day. All recorded history and "the history of the world" lies within the boundaries of the Holocene
Holocene
epoch.[18] Human activity is blamed for a mass extinction that began roughly 10,000 years ago, though the species becoming extinct have only been recorded since the Industrial Revolution. This is sometimes referred to as the "Sixth Extinction". Over 322 species have become extinct due to human activity since the Industrial Revolution.[19][20] Animal life[edit] Early in the Cenozoic, following the K-Pg event, the planet was dominated by relatively small fauna, including small mammals, birds, reptiles, and amphibians. From a geological perspective, it did not take long for mammals and birds to greatly diversify in the absence of the dinosaurs that had dominated during the Mesozoic. Some flightless birds grew larger than humans. These species are sometimes referred to as "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. Early animals were the Entelodon
Entelodon
(a so-called "hell pig"), Paraceratherium
Paraceratherium
(a hornless rhinoceros relative) and Basilosaurus
Basilosaurus
(an early whale). The extinction of many large diapsid groups, such as flightless dinosaurs, Plesiosauria
Plesiosauria
and Pterosauria
Pterosauria
allowed mammals and birds to greatly diversify and become the world's predominant fauna. Tectonics[edit] Geologically, the Cenozoic
Cenozoic
is the era when the continents moved into their current positions. Australia-New Guinea, having split from Pangea
Pangea
during the early Cretaceous, drifted north and, eventually, collided with South-east Asia; Antarctica
Antarctica
moved into its current position over the South Pole; the Atlantic Ocean
Atlantic Ocean
widened and, later in the era (2.8 million years ago), South America
South America
became attached to North America
North America
with the isthmus of Panama. India collided with Asia
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.[21] The break-up of Gondwana in Late Cretaceous
Cretaceous
and Cenozoic
Cenozoic
times led to a shift in the river courses of various large African rivers including the Congo, Niger, Nile, Orange, Limpopo and Zambezi.[22] Climate[edit] The Paleocene– Eocene
Eocene
Thermal Maximum at about 55.5 million years ago was a significant global warming event; however, since the Azolla event
Azolla event
of 49 million years ago, the Cenozoic
Cenozoic
Era has been a period of long-term cooling. After the tectonic creation of Drake Passage at 41 million years ago, when South America
South America
fully detached from Antarctica
Antarctica
during the Oligocene, the climate cooled significantly due to the advent of the Antarctic Circumpolar Current which brought cool deep Antarctic water to the surface. The cooling trend continued in the Miocene, with relatively short warmer periods. When South America
South America
became attached to North America
North America
creating the Isthmus of Panama
Isthmus of Panama
around 2.8 million years ago, the Arctic region cooled due to the strengthening of the Humboldt and Gulf Stream currents,[23] eventually leading to the glaciations of the Quaternary ice age, the current interglacial of which is the Holocene
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
Cenozoic
Era occurring with the common fundamental periodicity of ∼13 Myr
Myr
during most of the time.[24] Life[edit] During the Cenozoic, mammals proliferated from a few small, simple, generalized forms into a diverse collection of terrestrial, marine, and flying animals, giving this period its other name, the Age of Mammals, despite the fact that there are more than twice as many bird species as mammal species. The Cenozoic
Cenozoic
is just as much the age of savannas, the age of co-dependent flowering plants and insects, and the age of birds.[25] Grass
Grass
also played a very important role in this era, shaping the evolution of the birds and mammals that fed on it. One group that diversified significantly in the Cenozoic
Cenozoic
as well were the snakes. Evolving in the Cenozoic, the variety of snakes increased tremendously, resulting in many 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 gastornithid birds, terrestrial crocodiles like Pristichampsus, and a handful of primitive large mammal groups like uintatheres, mesonychids, and pantodonts. But as the forests began to recede and the climate began to cool, other mammals took over. The Cenozoic
Cenozoic
is full of mammals both strange and familiar, including chalicotheres, creodonts, whales, primates, entelodonts, saber-toothed cats, mastodons and mammoths, three-toed horses, giant rhinoceros like Indricotherium, the rhinoceros-like 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. See also[edit]

Cretaceous– Paleogene boundary (K–T boundary) Geologic time scale Mesozoic Paleozoic Phanerozoic
Phanerozoic
Eon

References[edit]

^ "Cenozoic". Dictionary.com Unabridged. Random House.  ^ "Cenozoic". Merriam-Webster
Merriam-Webster
Dictionary.  ^ "Cenozoic". Online Etymology Dictionary.  ^ "Cainozoic". Dictionary.com Unabridged. Random House.  ^ Oxford English Dictionary Second Edition, 1989 ^ Gibbard, P. L.; Head, M. J.; Walker, M. J. C. (2010). "Formal ratification of the Quaternary
Quaternary
System/Period and the Pleistocene Series/Epoch with a base at 2.58 Ma". Journal of Quaternary
Quaternary
Science. 25 (2): 96–102. Bibcode:2010JQS....25...96G. doi:10.1002/jqs.1338.  ^ International Stratigraphic Chart ^ Royal Tyrrell Museum (2012-03-28), Lamniform sharks: 110 million years of ocean supremacy, retrieved 2017-07-12  ^ University of California. " Eocene
Eocene
Epoch". University of California.  ^ University of California. " Eocene
Eocene
Climate". University of California.  ^ National Geographic Society. "Eocene". National Geographic.  ^ University of California. "Oligocene". University of California.  ^ Encyclopædia Britannica. "Neogene". Encyclopædia Britannica.  ^ University of California. "Miocene". University of California.  ^ University of California. "Pliocene". University of California.  ^ Jonathan Adams. " Pliocene
Pliocene
climate". Oak Ridge National Library. Archived from the original on 25 February 2015.  ^ University of California. "Pleistocene". University of California.  ^ University of California. "Holocene". University of California.  ^ Scientific American. " Sixth Extinction
Sixth Extinction
extinctions". Scientific American.  ^ IUCN. "Sixth Extinction". IUCN.  ^ Allen, M. B.; Armstrong, H. A. (2008). "Arabia-Eurasia collision and the forcing of mid Cenozoic
Cenozoic
global cooling". Palaeogeography, Palaeoclimatology, Palaeoecology. 265 (1–2): 52–58. doi:10.1016/j.palaeo.2008.04.021.  ^ Goudie, A.S. (2005). "The drainage of Africa
Africa
since the Cretaceous". Geomorphology. 67 (3–4): 437–456. doi:10.1016/j.geomorph.2004.11.008.  ^ "How the Isthmus of Panama
Isthmus of Panama
Put Ice in the Arctic". Oceanus Magazine.  ^ Chen, J.; Kravchinsky, V.A.; Liu, X. (2015). "The 13 million year Cenozoic
Cenozoic
pulse of the Earth". Earth and Planetary Science Letters. 431: 256–263. Bibcode:2015E&PSL.431..256C. doi:10.1016/j.epsl.2015.09.033.  ^ "The Cenozoic
Cenozoic
Era". 

Bibliography[edit]

British Caenozoic Fossils, 1975, The Natural History Museum, London. Geologic Time, by Henry Roberts. After the Dinosaurs: The Age of Mammals, by Donald R. Prothero, Bloomington, Indiana: Indiana University Press, 2006. ISBN 978-0-253-34733-6.

External links[edit]

Wikisource
Wikisource
has the text of the 1911 Encyclopædia Britannica article Cainozoic.

Wikimedia Commons has media related to Cenozoic.

Western Australian Museum – The Age of the Mammals

v t e

Geologic history of Earth

Cenozoic
Cenozoic
era¹ (present–66.0 Mya)

Quaternary
Quaternary
(present–2.588 Mya)

Holocene
Holocene
(present–11.784 kya) Pleistocene
Pleistocene
(11.784 kya–2.588 Mya)

Neogene
Neogene
(2.588–23.03 Mya)

Pliocene
Pliocene
(2.588–5.333 Mya) Miocene
Miocene
(5.333–23.03 Mya)

Paleogene (23.03–66.0 Mya)

Oligocene
Oligocene
(23.03–33.9 Mya) Eocene
Eocene
(33.9–56.0 Mya) Paleocene
Paleocene
(56.0–66.0 Mya)

Mesozoic
Mesozoic
era¹ (66.0–251.902 Mya)

Cretaceous
Cretaceous
(66.0–145.0 Mya)

Late (66.0–100.5 Mya) Early (100.5–145.0 Mya)

Jurassic
Jurassic
(145.0–201.3 Mya)

Late (145.0–163.5 Mya) Middle (163.5–174.1 Mya) Early (174.1–201.3 Mya)

Triassic
Triassic
(201.3–251.902 Mya)

Late (201.3–237 Mya) Middle (237–247.2 Mya) Early (247.2–251.902 Mya)

Paleozoic
Paleozoic
era¹ (251.902–541.0 Mya)

Permian
Permian
(251.902–298.9 Mya)

Lopingian
Lopingian
(251.902–259.8 Mya) Guadalupian
Guadalupian
(259.8–272.3 Mya) Cisuralian
Cisuralian
(272.3–298.9 Mya)

Carboniferous
Carboniferous
(298.9–358.9 Mya)

Pennsylvanian (298.9–323.2 Mya) Mississippian (323.2–358.9 Mya)

Devonian
Devonian
(358.9–419.2 Mya)

Late (358.9–382.7 Mya) Middle (382.7–393.3 Mya) Early (393.3–419.2 Mya)

Silurian
Silurian
(419.2–443.8 Mya)

Pridoli (419.2–423.0 Mya) Ludlow (423.0–427.4 Mya) Wenlock (427.4–433.4 Mya) Llandovery (433.4–443.8 Mya)

Ordovician
Ordovician
(443.8–485.4 Mya)

Late (443.8–458.4 Mya) Middle (458.4–470.0 Mya) Early (470.0–485.4 Mya)

Cambrian
Cambrian
(485.4–541.0 Mya)

Furongian (485.4–497 Mya) Series 3 (497–509 Mya) Series 2 (509–521 Mya) Terreneuvian
Terreneuvian
(521–541.0 Mya)

Proterozoic
Proterozoic
eon² (541.0 Mya–2.5 Gya)

Neoproterozoic era (541.0 Mya–1 Gya)

Ediacaran
Ediacaran
(541.0-~635 Mya) Cryogenian (~635-~720 Mya) Tonian (~720 Mya-1 Gya)

Mesoproterozoic era (1–1.6 Gya)

Stenian (1-1.2 Gya) Ectasian (1.2-1.4 Gya) Calymmian (1.4-1.6 Gya)

Paleoproterozoic era (1.6–2.5 Gya)

Statherian (1.6-1.8 Gya) Orosirian
Orosirian
(1.8-2.05 Gya) Rhyacian (2.05-2.3 Gya) Siderian
Siderian
(2.3-2.5 Gya)

Archean
Archean
eon² (2.5–4 Gya)

Eras

Neoarchean (2.5–2.8 Gya) Mesoarchean (2.8–3.2 Gya) Paleoarchean
Paleoarchean
(3.2–3.6 Gya) Eoarchean
Eoarchean
(3.6–4 Gya)

Hadean
Hadean
eon² (4–4.6 Gya)

 

 

kya = thousands years ago. Mya = millions years ago. Gya = billions years ago.¹ = Phanerozoic
Phanerozoic
eon. ² = Precambrian
Precambrian
supereon. Source: (2017/02). International Commission on Stratigraphy. Retrieved 13 July 2015. Divisions of Geologic Time—Major Chronostratigraphic and Geochronologic Units USGS Retrieved 10 March 2013.

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