Life Throughout the Oligocene
climates in the interior of North America led to fewer sites where
plant fossils were preserved, but there is some evidence for more
open forests. Grasslands may have developed in some areas but were
probably not widespread. Along the west coast of North America, relatively
diverse forests of broad-leaved trees and conifers
were common. In higher northern latitudes, forests consisted of broad-leaved
deciduous trees and conifers.
Ungulates were remarkably diverse in the Oligocene.
Among the even-toed forms (artiodactyls),
(imagine an animal with pig-like feet but molar teeth more like those
of a cow) were very abundant in North America. Pig-like entelodonts
roamed the continents alongside ruminants such as
camels. Odd-toed ungulates (perissodactyls)
included herds of three-toed horses and many forms
of rhinoceros. These diverse Oligocene rhinos included
agile running forms, and in Asia, the largest land mammals of all,
the giant indricotheres. Carnivorans
included early members of the dog and cat families, including saber-toothed
cats. South America, which had been isolated from other continents
for millions of years, developed a unique fauna that included edentates
(armadillos and sloths), predatory
marsupials (borhyaenids), and giant
carnivorous ground birds (phorusrhacids).