We explain what the Cenozoic Era is, how it is divided and why it is so important. Also, what are its characteristics, flora and fauna.

Cenozoic eraCenozoic era
The Cenozoic is considered the “Age of Mammals”.

What is the Cenozoic Era?

What is known as the Cenozoic Era or also Cenozoic (and formerly as the Tertiary Era) is the last division of the geological time scalewithin what makes up the Phanerozoic Eon (started 541 million years ago and culminates in our present days), together with the Paleozoic and Mesozoic eras.

The Cenozoic Era began with the extinction of the dinosaurs 66 million years ago about. His name comes from the Greek words kainos (“new and zoe (“life”, “animal”), thus meaning “new life”.

It is also known as the “Age of Mammals”, since this was the privileged way of life throughout its 66 million years of duration. In addition, it is the Era in which the human being made its appearance.

See also: Paleolithic

previous era

In the Mesozoic Era the world was populated by dinosaurs. They were enormous lizards that reigned for one hundred and sixty million years.

Nevertheless, went extinct abruptly at the end of the Cretaceous period (the last of the Mesozoic era, after the Triassic and Jurassic).

This was the era in which the first mammals arose, and in which the supercontinent of Pangea began to break apart and give rise to the geography we know today.

Division of the Cenozoic Era

Cenozoic eraCenozoic era
The Quaternary period lasted until the rise of human civilization.

The Cenozoic Era was divided into three periods, each subdivided in turn into 2 or 3 epochs and these into a varied number of ages. Everything is detailed below:


  • Paleogene period. It begins 66 million years ago and lasts until approximately 28.1 million years ago. It is divided into three periods:
    • Paleocene. From 66 million years ago to 59.2 million years ago, comprising the Danian, Selandian and Thanetian ages.
    • Eocene. From 56 million years ago to 38 million years ago, including the Ypresian, Lutecian, Bartonian, and Priabonian ages.
    • Oligocene. From 33.9 million years ago to 28.1 million years ago, comprising the Rupelian and Chattian ages.
  • Neogene period. It begins 23 million years ago and ends approximately 3.6 million years ago. It comprises two periods:
    • Miocene. From 23 million years ago to 7.2 million years ago, spanning the Aquitanian, Burdigalian, Langhian, Serravalian, Tortonian, and Messinian ages
    • Pliocene. From 5.3 million years ago to 3.6 million years ago, spanning the Zanclian and Piacenzian ages.
  • Quaternary period. From 2.5 million years ago until the emergence of human civilization (and the beginning of History), covering two eras:
    • Pleistocene. From 2.5 million years ago to about 126,000 years ago, spanning the Gelasian, Calabrian, Ionian or Middle Pleistocene and Tarantian or Upper or Late Pleistocene ages.
    • Holocene. From approximately 11,700 years ago to the present, without ages.
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Formerly, the Paleogene and Neogene periods were joined in a “Tertiary Period”. But such consideration is no longer in use.

Geological features of the Cenozoic

Cenozoic Era - The AlpsCenozoic Era - The Alps
When Arabia collided with Eurasia, the Alpine orogeny occurred.

During the Cenozoic, the supercontinents of Gondwana and Laurasia separated. That is the continents were acquiring their current orientation and position. The Atlantic Ocean widened and then the two American continents (North and South, with the creation of the Central American Isthmus) joined.

Other important geological events during the Cenozoic were the collision between the Indian subcontinent and the Asian continent 55 to 45 million years ago. This is how the formation of the Himalayas was triggered.

Similarly, Arabia collided with Eurasia 35 million years ago. As a consequence, the Tethys Sea was definitively closed, and the orogeny of the Alps took place. Those processes continue today.

Climate of the Cenozoic Era

The climate of the Cenozoic It’s been from a long term chill. Initially it was due to sun blocking which produced ash from the K-Pg Event (the extinction of the dinosaurs) in the atmosphere.

Later it continued due to the distance of the continents and the appearance of the Antarctic Circumpolar Current, which allowed the cooling of polar waters. The same thing happened with the Humboldt and Gulf currents with the Arctic region.

The “Ice Ages”

Cenozoic eraCenozoic era
In the interglacial periods the cold decreased and the ice receded.

The Quaternary is understood as a period of fluctuations in the ice level in the polar regions, more or less stable cycles that oscillated 100,000 years. Some estimates indicate that there were around 80 glaciations throughout the period, generating glacial periods or “ice ages”.

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During the ice ages, the ice sheets expanded, the seas receded and the global climate cooled and dried. But in the interglacial periods, the cold decreased and the ice receded, releasing water into the oceans.

In the last million years 4 main major ice ages would have occurredwith their respective intermediate periods: Günz Glaciation (1.1 million years ago), Mindel Glaciation (580,000 years ago), Riss Glaciation (200,000 years ago) and Würm Glaciation (80,000 years ago).

Flora of the Cenozoic Era

cenozoic era flora herbscenozoic era flora herbs
In the Cenozoic era, herbs and grasses arose in more arid areas.

Thanks to the disappearance of the dinosaurs, in the Cenozocio the vegetation was able to expand and diversify, especially during the first times, more humid and warm. Subsequently, the forests began to give way to drier and more arid areas. This is how grasses and herbs arose.

Finally, the hand of the human made itself felt in this area: the edible and cultivable species began to predominate in many aspects. This was due to human intervention and the development of agriculture.

Continental separation also allowed for greater diversification. Thanks to the isolation of continental ecosystems for thousands of years, many species gave rise to new ones.

Fauna of the Cenozoic Era

At the beginning of the Era, the surviving species of the Cretaceous-Paleogene Mass Extinction were mostly small mammals, reptiles and birds. That is why they were the ones that proliferated more and faster, stripped of their great predators.

among mammals were the rodents and small horses. Its biggest predators became large flightless birds, such as those belonging to the genus titans.

The first primates appeared in the Neogene., and among them the first hominins, ancestors of the human race. Cattle, antelopes, gazelles, and other large mammals flourished during this period, as did aquatic mammals such as whales.

Finally, the Quaternary was characterized by the presence of big cat predatorsLike saber-toothed tigers. Woolly mammoths, adapted to ice ages, also proliferated.

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The presence of humans influenced the fate of many of these species. Some of them found their extinction due to the increase in hunting by this new species that little by little became the dominant one on the entire planet.

Evolution of Humanity

Cenozoic eraCenozoic era
Homo sapiens is the only species not extinct today.

In the Quaternary period humanity makes its entrance. It is the result of a slow process of evolutionary changes from the first hominins that emerged on the African continent: species of the genus australopithecus and subsequently Homo.

When they migrated to Eurasia and the Near East, they gave rise to new human species. The last ones were homo neanderthalensis (“Neanderthal Man”), Homo denisovensis (“Denisovan hominid”) and the Homo sapiensthe only species not extinct today and the only one that we currently understand as “Humanity”.

Disuse of the term “Tertiary”

Nowadays the name Cenozoic Era is preferred for the total time span between the extinction of the dinosaurs and the present, rather than the Tertiary Era. This is because the previous Eras are also no longer referred to as Primary and Secondary.

Furthermore, the Cenozoic period, which was commonly called the Tertiary Period, is preferred to be treated as two distinct periods: Paleogene and Neogene. However, the Quaternary name is maintained.

Importance of the Cenozoic Era

Cenozoic eraCenozoic era
The Cenozoic is a revival of life in a new key, mammals.

The Cenozoic Era offers us the explanation of how the prehistoric world came to be as it was at the beginning of our civilization. So, It is the context of the beginning of our history as a species.

The geological, climatic and biotic changes that occurred during its 66 million years directly define what we find today in the various ecosystems. They are also the origin of the resources of the soil in which we sow and the seas from which we feed.

On the other hand, the Cenozoic represents a reflowering of life in a new key: the mammals. From them eventually emerged the human species.


  • “Cenozoic Era” on Wikipedia.
  • “Cenozoic Era: History and Characteristics” at Centro Estudios Cervantinos.
  • “Cenozoic Era” at Erthzel.com.
  • “The Cenozoic Era” at the University of California Museum of Paleontology.
  • “Cenozoic Era: Facts about Climate, Animals & Plants” in Live Science.
  • “Cenozoic Era” in The Encyclopaedia Britannica.

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