TERTIARY PERIOD (66-6 million years ago)
This period is subdivided into 5 epochs.
Paleocene epoch (65-55 million years
ago)
The climat was cool and temperate. There were many angiosperms that are now
extinct. Radiation of primitive placental mammals took place. Mammals started to fill the
place vacated by dinosaurs.
Eocene Epoch (55-36 million years ago)
  In the angiosperm forests one of the most
numerous plants were the sequoias. Many of the modern genera of plants already existed
(maples, dogwoods, walnuts, elms, beeches). The placental mammals (group including the
monkey, the pig, the horse, the camel, the rat) were present. The marine mammals,
ancestors of the whales and sea cows, establish themselves in the seas. The small horse
"Eohippus" appeared. Tropalaeotherium was a primitive
perissodactylous animal.Diatryma was a carnivorous bird that lived in North
America.
Photos of Tropalaeotherium, Diatryma courtesy of Museum of
Evolution in Warsaw
  
   
Oligocene Epoch (36-25 million years ago)
Tropical forests were distributed worldwide. The number onocots (relatives of
grasses) increase. There were flowering plants. The archaic carnivorans were replaced by
the true ones. The early larger horse "Mesohippus" evolved from the
"Eohippus". The turtles, the alligator, and crocodiles developed.
Anthropoids (monkeys) appeared. Many common kinds of insects genera were already
present.
Miocene Epoch (25-6 million years ago)
The northern flora diminish its extent. There was an esential reduction of forests.
The first seal appeared. Modern mammals were rapidly developing especially in North
and South America. In South America there were the carnivorous marsupials and the giant
sloth. The North American fauna included primitive dogs, camels and elephants. The
three-toed horse ("Merychippus") had evolved. Invertebrates became more
modern. The anthropoids were more advanced.
Pliocene Epoch (6-1.7 million years ago)
   Dimish of northen flora and reduction of forests
continued as the area of grassland increased. Herbaceous dicots became more numerous while
woody dicots went into a decline. The Iivertebrates in oceans as well as the placental
mammals were nearly identical with the contemporary formes. Camels, antelopes, mastodons,
and all types of carnivores were present. The one-toed horse "Pliohippus"
appeared. The upright human body evolved. Similarity of early hominids with certain
anthropoids is apparent.
Photos of horse, nastodon, aurochs courtesy of Museum of Evolution in
Warsaw
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