The Tertiary Period:
The Age Of Mammals Begins

The Tertiary Period Is the old name given to the first period of the Cenozoic Era. It is no longer an official term and has been replaced by the Paleogene Period for the first 3 Epochs while the next 2 now belong to the Neogene Period. It may be a little confusing and why change the name anyway? Well the name Tertiary was first used in the mid 18th century. At that time all of geologic time was divided into only 3 periods, Primary, Secondary, and Tertiary. Later a fourth period was added not mysteriously called Quaternary.

A lot has been learned since that time and many divisions have been added to organize our understanding of geologic time. We now have Eons, Eras, Periods, and epochs. Each of those divisions have divisions. See the currently recognized Geologic Time Line. The old system using 4 time periods could no longer be helpful. Yet 2 of the old terms were still in use until recently, the Tertiary and the Quaternary. As of 2013 the Tertiary is gone. The Quaternary remains.

The remainder of this page details the Tertiary of old. For more current divisions see the links above: Paleogene Period, Neogene Period, and the Geologic Timeline.

The Tertiary Period began 65 million years ago and lasted more than 63 million years, until 1.8 million years ago. The Tertiary is made up of 5 epochs :

The Paleocene Epoch - 65 to 54 million years ago
The Eocene Epoch - 54 to 38 million years ago
The Oligocene Epoch - 38 to 24 million years ago
The Miocene Epoch - 24 to 5 million years ago
The Pliocene Epoch- 5 to 1.8 million years ago

Each epoch has unique characteristics for climate and geography. The plants and animals changed from epoch to epoch also.

In the early 1800’s a system for naming geologic time labeled only four periods. They were named using the Latin forms of numbers for first, second, third and fourth. The word tertiary means “third.” It was the third period in this system. Today, we use a different system, but the name Tertiary is still common for the first part of the Cenozoic Era. Today’s system looks like this:

Era	Traditional Periods	New Periods	Epochs
C E N O Z O I C E R A	Quaternary Period	Neogene Period	Holocene Epoch
			Pleistocene Epoch
	Tertiary Period		Pliocene Epoch
			Miocene Epoch
		Paleogene Period	Oligocene Epoch
			Eocene Epoch
			Paleocene Epoch

Tertiary Climate: A Cooling Trend From Tropics To Ice Age
The beginning of this period was very warm and moist compared to today’s climate. Much of the earth was tropical or sub-tropical. Palm trees grew as far north as Greenland! By the middle of the tertiary, during the Oligocene Epoch, the climate began to cool. This cooling trend continued and by the Pliocene Epoch an ice age had begun.

Period	Epoch	Continental Positions	New Mammals
N e o g e n e	Pliocene	Africa closes off the Mediterranean Sea North and South America join at Panama The Geography of the earth similar to today	First hominids-human ancesters
N e o g e n e	Miocene	Africa is pushing into Europe-forms the Alps Arctic becomes covered with ice	Horses,camels,and rhinos Beaver-like animals many apes and other primates
P a l e o g e n e	Oligocene	Australia separates from Antarctica India crashes into Asia-forms Himalayans Antarctica is covered by glaciers Sea levels are low	Dogs, cats, and pigs toothed whales
	Eocene	Europe and North America separate	Bats Elephant ancestors Whales Eohippus-the first horse
	Paleocene	Europe is joined with North America Australia is joined with Antarctica India a land unto itself Atlantic Ocean is forming	The condylarths-ancestors of modern hoofed herbivores Rodents The first Primates

Grasses Support Grazing Animals
The plants of the Tertiary are very similar to the plants that we have today. The warm climate at the beginning of the period favored dense forests. As the climate cooled open woodlands and grasslands became abundant. The grasses were important because they supported huge herds of grazing animals.

The Rise of The Mammals
The extinction event at the close of the Cretaceous Period wiped out the dinosaurs, large reptiles, and many other species. This left room for new animals to develop. The mammals became the dominant animals. In fact, the Cenozoic Era is often called the Age of Mammals. Most of the main groups of mammals were present by the Eocene Epoch. With the dinosaurs and other large reptiles gone mammals grew in size, numbers and diversity. They filled ecological niches in the sea on land and in the air. The table above shows what mammals came on the scene with each new epoch.

Hominids: Human Ancestors
During the Pliocene the first hominids appeared; these were our human ancestors!

The Tertiary Was For The Birds
Birds did almost as well as mammals during the Tertiary Period. Many of the birds we know today were present. There were also many large flightless birds that are now extinct. These birds did particularly well before the mammals developed so many species.

Boney Fish and Sharks Develop New Species
Fish species branched out during the Tertiary Period. Sharks became more plentiful. Trout and bass evolved.

Flowering Plants Means Nectar For Insects
The insect population increased in the Tertiary Period. Bees and other insects that lived on pollen and nectar of the flowering plants prospered.

The Tertiary Period Ends With An Ice Age and Land Bridges
The cooling climate of the Tertiary Period led to huge glaciers at the poles. The mountains of the world were also covered by glaciers, including the newly formed Himalayas and Alps. The huge amounts of water locked up in the ice lowered the level of the sea and land bridges appeared: