Paleogene Period

65.5 - 23.03 million years ago

The Paleogene Period - (also referred to as the ) includes the Paleocene, Eocene , and Oligocene epochs. This was the dawn of the "age of mammals", where several ecological niches were left vacant after the dinosaurs (and many other species) died out during the K-P Mass Extinction Event; this allowed mammals to fill these gaps. The climate was still very hot, and some places had high amounts of rainfall. Large expanses of land were tropical rainforests and wetlands. Towards the end of this period, a huge ice cap had finally formed over Antarctica; this probably altered the Earth's climate. Which means many of the warm habitats were replaced by temperate habitats such ass deciduous and coniferous forests.

Fauna
Even with these niches open, there weren't any large mammals at the beginning of the Paleogene. Most had appeared around the end of the Eocene epoch, including the dinoceratans; which were an order of large, rhinoceros-like mammals with distinctive knobs atop their heads and tusk-like teeth. Unfortunatly they died out during the middle of this period. Carnivorous mammals had yet to appear; first it was the birds who gave it a try, bringing such forms as Gastornis, with a large beak to tear prey apart. Reptilian and amphibian animals were doing very well in the humid climate, being able to florish in the lush wetlands and forests. With the extinction of the large marine reptiles during the end of the Cretaceous, mammals began to fill the niche; whales. The first whales were very primitive, otter-like animals that lived both on land and water.

Terrestrial Animals
Notharctus 

Darwinius

Amphicyon

Eusmilus

Uintatherium

Didolodus

Mesonyx

Andrewsarchus

Phenacodus

Arsinoitherium

Moeritherium

Phiomia

Mesohippus

Gastornis

Titanoboa

Pristichampsus

Aquatic Animals
Ambulocetus

Basilosaurus

Prosqualodon

Aerial Animals
Icaronycteris

Presbyornis