Cenozoic Era: Animals, Periods, and When It Happened

Written by Austin S.
Published: May 31, 2022
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Evolution has taken life on earth through different types of species. The evolution of life on Earth is classified into different eras and periods. These periods are identified by popular species of the time or notable events in history. 

They include giant animals, both herbivores and carnivores. The giant animals died out due to some natural events or evolved to fit modern standards. This article will discuss the Cenozoic era and the epochs within it. We will also discuss the types of animals that evolved and went extinct and how the climate changed in this era.

What is the Cenozoic era?

The Cenozoic period describes the beginning of the evolution of modern life on Earth. This era started around 65 million years ago after the Cretaceous period. The Cretaceous extinction events gave way to the evolution of the Cenozoic era. The extinction event destroyed all dinosaur life. This event gave way for modern animals to start evolving. The Cenozoic era continues to this day.

The Cenozoic era got its name from the Greek language. It means ‘modern life’. The Cenozoic era features the shifting of the continents to their current positions. This era is also famous as the age of mammals.  The Cenozoic era allowed mammals to flourish in the absence of dinosaurs. 

Mammals evolved to fill the spaces left by the dinosaur extinction. Smaller mammals grew bigger during this period. These mammals also took the dominating position dinosaurs had over other animals. The Cenozoic era can be divided into three periods. They are:

Paleogene period

The Paleogene period started after about two million recovery years after the Cretaceous extinction. The earth rapidly refilled the ecosystem. The lands and air were roaming with animals and birds of the time. Marine life was also present, almost exactly like what we have today.

Neogene period

In this period, grasslands became more vast, allowing more mammals to evolve. The climate also became cooler and less moist. Marine life flourished, with sharks growing to their prime sizes. Savannahs vastly covered forests allowing new types of food to evolve.

Megalodon (Carcharocles megalodon)
Megalodons are an extinct species of sharks that grew to more than 50 feet in length.


Quaternary period

This period features irregular climate activities. These irregular activities led to the extinction of many animals from Earth. This extinction happened cos sources of food were severely affected by climate change

This ending period of the Cenozoic era also features man’s rise as a predator in the ecosystem. These periods lasted over millions of years and have different epochs within them. These subperiods better explain specific points of evolution in history.

The different Epochs in the Cenozoic periods

There are certain subperiods within the Cenozoic era. These subperiods give a more detailed breakdown of how evolution events occurred in this era. It can also point to the species of animals that went extinct in this era. The epochs within the Cenozoic periods are:

The Paleogene period

This period lasted between 65 to 23 million years ago. Its epochs are; 

Paleocene epoch

The Paleocene epoch lasted between 65.5 to 55.8 million years ago. This period features experiments with evolution as small mammals and birds filled the ecosystem. Plants started to flower, and grasses began to grow.

This sea life featured sharks, turtles, bony fish, and crocodilians. The waters were dominated by bony fish and sharks, as it still is today. The epoch ends with a quick rise in temperature around the world.

Eocene epoch

The Eocene epoch lasted between 55.8 to 33.9 million years ago. This period starts with the hottest period of the Cenozoic era, about five million years. The Global warming happening then was due to a high release of methane from the ocean floor.

Polar regions also allowed the growth of trees as a response. This epoch featured the evolution of mammals with odd toes. Mammals like rhinos, horses, and camels are included.

Oligocene epoch

This epoch starts the process of cooling the earth into the ice age. Grasslands started to cover spaces where forests had disappeared. Anthropoid apes evolved in this epoch. There were different species of rhinoceros, including Indricothere. 

The Oligocene epoch also saw Antartica separate from South America. This separation led to reduced global temperatures and permanent ice formation in Antarctica. 

Neogene period

This period lasted between 23 to 2.5 million years ago. Its epochs are:

Miocene epoch

The Miocene epoch lasted between 23 to 5.3 million years ago. This epoch is the second-longest in the Cenozoic era because it covers most of the Neogene period. Though this epoch began with a warm temperature, it later cooled down to fit the Cenozoic climate. The vast grasslands became home to a new set of mammals.

Animals like horses abandoned forests for grazing in the grasslands. There was a change in the ocean circulation. This change caused the evolution of various marine animals. These animals include seals, sea cows, baleen whales, and sea lions.

Cenozoic era
The Miocene epoch saw the evolution of sea lions, much as we see them today.


Pliocene epoch

This epoch lasted between 5.3 to 2.5 million years ago. It started with the collision of the Eurasiasian continents and Africa. This collision caused the Mediterranean basin to dry up and turn into grasslands. This basin was later refilled from the Atlantic ocean when the Western barrier was breached.

The Pliocene epoch also features the forming of the Panamanian bridge. This bridge was between South and North America. It allowed animals from both regions to interact. Savannahs and grasslands remained a grazing ground for herbivores. 

Quaternary period 

This period started about 2.5 million years ago and is still ongoing. Its epochs so far are:

Pleistocene epoch

The Pleistocene epoch lasted between 2.5 to 0.01 million years ago. The evolution of modern humans began in this epoch. Human species like Homo erectus, Homo sapiens, and Homo neanderthalensis evolved in this epoch. It also features frequent glaciation cycles with at least 20 in this epoch. 

Some of these glaciations covered about 30% of Earth. The extinction of many massive mammals happened in this epoch. There have been speculations that hunting by humans rapidly led to these extinctions.

Holocene epoch

This epoch is the current era of evolution. It started about 12,000 years ago. It is also called the Anthropocene epoch. The Holocene epoch features varieties of changes due to human activities. Humans have made lots of artificial changes to the earth. The extinction of animal species and global warming are part of these changes. 

Animals of the Cenozoic era

The Cenozoic era features the rise of man to dominate all species. Humans became the prime predators and got to the top of the food chain. There were other giant mammals that existed during this period. 

Some modern animals also had various species that existed during this period. While marine life is similar to what we have today, there were more species in the waters during this era. This era also features the extinction of some of these animals, primarily due to human activities. 

The oceans expanded during this period which allowed for diversifying species of many marine mammals. Marine life featured Corals, Megalodon sharks and whales of different species. When The Great Lakes were formed, they housed trouts, bass, and other freshwater fish species. Marine reptiles from the dinosaur era also evolved to fit the new ecosystem. These reptiles include the crocodilians and turtles. 

Paleogene Epoch 

The Paleogene epoch begins with the evolution of surviving mammals from the Cretaceous period into the new world. At the conclusion of this period, dogs, cats, and pigs were rampant. Smaller animals like Hyracotherium, a rodent, and miniature horses evolved later. Other modern-day land mammals, such as rhinoceroses and elephants, make an appearance. 

Neoprene period

The Neogene period allowed ruminant animals to flourish. The vast grasslands became grazing land. Animals like horses, camels, bison and sheep grew stronger. They also evolved to develop stomachs that digest grass well.

These animals quickly became roamers on earth and developed herd movement, serving as a survival tip. Sharks ruled the oceans in this period. The Megalodon sharks evolved in this period. This shark is the largest ever at about 15 meters in length. Apes evolved and diversified in Africa and Asia

Quaternary Period

The Quaternary period was relatively cold in this era. Animals prioritized warmth. Ocean life remained topped by sharks and whales. Mammals grew lots more hair in this period. Mammals like bison, rhinos, oxen, and mammoths grew hair coats for protection from the cold and ice.

As the climate warmed up, some of these animals went extinct. This extinction ended the ice age. Animals like mammoths went extinct in this period.

The Quaternary period is famous as the age of humans. The earliest set of modern humans was from Africa. They developed bigger brains and became more intelligent. These humans dispersed to other continents and evolved to fit the new environment.

Humans have dominated the animals on the earth since our arrival about 190,000 years back. Human activities have also caused many changes to life on earth, even making some animals go extinct through hunting.

denisovan vs neanderthal
Neanderthal adult male, based on 40000-year-old remains found at Spy in Belgium


©IR Stone/Shutterstock.com


The Cenozoic era is the human era. This era has seen humans evolve and develop into civilized animals. It started with the earth adjusting to new hopes after the Cretaceous extinction. This new life evolved to fit the new earth’s climate and environment.

As humans evolved, intelligence grew, and the world changed from what it has always been. Evolution is still ongoing as we are still in the Cenozoic era.

The photo featured at the top of this post is © iStock.com/Denis-Art

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About the Author

Growing up in rural New England on a small scale farm gave me a lifelong passion for animals. I love learning about new wild animal species, habitats, animal evolutions, dogs, cats, and more. I've always been surrounded by pets and believe the best dog and best cat products are important to keeping our animals happy and healthy. It's my mission to help you learn more about wild animals, and how to care for your pets better with carefully reviewed products.

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