Terrestrial Life Throughout the Miocene
Horses
had begun to diversify early in the Neogene,
but most of these species were browsing
animals with low-crowned teeth. Their short legs were well suited to walking through closed,
forest-like environments. However, during the middle Miocene, one
group of these horses evolved durable teeth that allowed them to graze
(eat grasses); their high tooth crowns were better
able to withstand the tough, dusty grit on many grasses.
Other lines of browsing horses became extinct before the end of the
Miocene. Grazing horses diversified into several different forms,
but only two of these survived past the Miocene: a three-toed lineage
that became extinct in the ice ages, and a single-toed
lineage that gave rise to modern horses and zebras.
In the Great Plains and Asian steppes, grasses dominated
the landscape, with forests confined to stream courses and wet areas.
In wetter regions such as eastern North America, forests were dominant.
Grazers became more common than browsers among the mammals, with ruminants
enjoying particular success. Elephant-like gomphotheres
were the largest Miocene land mammals in North America. Although horned
and hornless ruminant mammals also
diversified, many species became extinct by the end of the Miocene.
Deer and giraffes flourished alongside
early mastodont elephants. The odd
chalicotheres, clawed perissodactyl
ungulates, also appeared, as did our own near ancestors in Africa,
the first anthropoid
apes.
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