Tertiary Period is the time span which belonged to the Cenozoic Era. This last era of Cenozoic was divided into Palaeogene, Neogene, and Quaternary periods and the Palaeogene and Neogene periods are collectively termed as Tertiary Period. Hence to study and know interesting facts about Tertiary Period is to know about the Palaeogene and Neogene periods.
The Palaeogene period is subdivided into Oligocene epoch, Ecoene epoch, and Palaeocene epoch. Each of these epochs contributed to the life forms, species and other factors of the Tertiary Period.

Palaeocene epoch: This epoch started 65 million years ago with the span of 10 million years. It is the first epoch of the Palaeogene period and the Cenozoic era and mainly known for the age of the mammals.

Species of Palaeocene epoch: Dinosaurs are no more in this period after they suffered from the mass extinction of the Cretaceous period. Mammals begin to expand in rapid way. Existence of Diatryma, the flightless birds are proved. Seas are occupied with dominant mollusks like gastropods and bivalves. Teleost fishes and sharks are also in abundance. Angiosperms or better known as flowering plants spread widely.

Eocene epoch: This epoch started 38 million years ago with the span of 17 million years. It is also one of the dominant part of the Palaeogene period and contributed in the development of life forms of the Palaeogene period.

Species of the Eocene epoch: Mammals are continuing their evolution in this epoch and many of them became dominants. Among the small mammals which were in dominance were the rodents. Hyracotherium, a type of small horses were also common. Early rhinoceroses along with elephants appeared in the scene. HugeUintatherium reaching the length of 10 feet or 3 metres also became prominent. Different types of owls, geese, herons, ducks and hawks are the major species of birds. Flowering plants are supported by the insects for their pollination. Seas are mainly occupied by Gastropods, Bivalves, and hexacorals. Crabs and different types of fishes, most of which are modern fishes also appeared in this period. Among the marine mammals whales appeared to dominate the seas.

Oligocene epoch: It is the 3rd and final epoch of the Palaeogene period. Started 38 million years ago this period lasted for 13 million years. The Palaeogene period ends with this period.

Species of Oligocene epoch: The prominent mammals of this period include dogs, pigs, rhinoceroses, peccaries, and cats. Horses also flourished in the Northern America while giant pigs like Archaeotherium and Gigantic Brontotheres roamed in North America and Asia. Armadillos, ground sloths, and camels also appeared in this epoch. Termites and ants are the dominant insects of this Oligocene epoch. The Tertiary period is also the period of the Neogene. In this period gazelle, antelope, sheep, goats and cattle dominate the land and the mammal fauna. Camels, peccaries, tapirs, elephants, rhinoceroses and horses were too in the scene with increasing number of beavers and ground squirrels. Among the typical Pliocene mammals are Deinotherium, Megatherium, and Macrauchenia.