#  Horse Environments Descriptions 

 



*Descriptions of the environments of five epochs in horse evolution.*

####  Eocene (55.8-33.9 MYA)

   ![Eocene Fauna (55.8-33.9 MYA)](/sites/g/files/omnuum10506/files/styles/hwp_1_1__960x960_scale/public/collectionsmcz/files/horse_environment_horiz_1_eocenekey.jpg?itok=jraRmOHT) 

 

**At the beginning of the Eocene, the climate was moist and warm. Forests covered almost all of the land, including the north and south poles. Fossils from this time show that subtropical and even tropical trees grew in in Greenland, and palm trees grew in Alaska. During the mid-Eocene, the climate started to cool and dry. Some forest areas thinned and were replaced by grasses but grassy areas had not yet expanded to become plains and savannas. By the end of the epoch, deciduous forests covered large parts of the northern continents, and rainforests only remained in equatorial South America, Africa, India and Australia.**

#### Oligocene (33.9-23 MYA)

   ![Oligocene Fauna (33.9 - 23 Ma)](/sites/g/files/omnuum10506/files/styles/hwp_1_1__960x960_scale/public/collectionsmcz/files/horse_environment_horiz_2_oligocenekey.jpg?itok=UQ6kQ-Er) 

 

**During the Oligocene, the climate cooled and dried. Grasses, favored in the cooler, drier climate, became one of the most important groups of organisms on the planet, while forests (especially tropical ones) shrank. Even at the end of the epoch, however, grass was not as common as one would observe in a modern savannah today. These new grasslands provided food for herds of grazing mammals. Grasses are high-fiber, low-protein plants that must be eaten in large quantities to provide adequate nutrition. They also contain tiny glass-like silica fragments, called phytoliths, which makes them tough to chew, and that also causes them to wear down animal teeth.**

#### Miocene (23-5.3 MYA)

   ![Miocene Fauna (23 - 5.3 MYA)](/sites/g/files/omnuum10506/files/styles/hwp_1_1__960x960_scale/public/collectionsmcz/files/horse_environment_horiz_3_miocenekey.jpg?itok=MJnznNdP) 

 

**In the Miocene, grasslands continued to expand while forests diminished. These expanding grasslands provided space and food for roaming herds of swift, grazing animals that gradually replaced the leaf-eating woodland mammals from earlier epochs. During this epoch, while temperatures rose again, a new type of photosynthesis evolved that allowed plants to survive better in hotter temperatures. Plants using this new "C4" system also took up more silica, which made them even tougher on the teeth of grazing mammals.**

#### Pliocene (5.3-2.6 MYA)

   ![Pliocene Fauna (5.3-2.6 MYA)](/sites/g/files/omnuum10506/files/styles/hwp_1_1__960x960_scale/public/collectionsmcz/files/horse_environment_horiz_4_pliocenekey.jpg?itok=QK9_JJkC) 

 

**During the Pliocene, a cooler, dry, seasonal climate had a considerable impact on vegetation. Coniferous forests and tundra covered much of the north, and grasslands spread on all continents (except Antarctica). Tropical forests shrank to a tight band around the equator, and dry savannahs and deserts appeared in Asia and Africa. In the higher latitudes, cool-weather plants evolved. Hardy plants that can tolerate a short growing season, such as sedges, mosses, and lichens, inhabited the almost permanently frozen tundra. In slightly warmer regions, taiga forests consisted mostly of evergreens. In lower latitudes, grasslands were marked by fewer and fewer trees. These habitats offered limited food sources for animals and supported less diversity.**

#### Pleistocene (2.6 MYA-10,000 YA)

   ![Pleistocene Fauna (2.6 MYA-10,000 YA)](/sites/g/files/omnuum10506/files/styles/hwp_1_1__960x960_scale/public/collectionsmcz/files/horse_environment_horiz_5_pleistocenekey.jpg?itok=Pswh6bo3) 

 

**During the Pleistocene, glaciers–some a mile thick–repeatedly advanced from the Arctic north over Europe and North America, then retreated. Temperatures dropped dramatically, profoundly affecting plants and animals. Mammoths, rhinos, bison, reindeer, and musk oxen evolved to have warm, woolly coats to protect them from frigid conditions. These new mammals fed on small bushes and hardy grasses that could tolerate the cold. When glaciers retreated, warm-weather plants such as oak and beech trees, lush grasses, and flowers, returned temporarily. During these "interglacial" periods, species that sought shelter in the warmer south returned to their old habitats.**

*Original art by:* **Xavier Moss**



 

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