During the Miocene (‘less new’ life), Africa collided with southern Europe (the impact formed the Alps), and India collided with southern Asia (this impact led to the formation of the Himalayas). An interchange of mammals between Africa, Europe and India was then possible. In the Pliocene, North and South America became linked by the Panama isthmus.
Ice-caped Antarctica continued to expand and the climate became steadily cooler. The more temperate climate favoured more open countryside rather than dense forests. Huge areas of grassland developed on the continents and this assisted mammal development because open grasslands can support far greater numbers than equivalent areas of forest.
As living in open spaces made the animals more conspicuous, most of the successful herbivores therefore became fast runners. Carnivores developed new pursuit strategies such as speed, endurance, stealth, and cooperative hunting.
The browsing (leaf-eating) horse Anchitherium (‘near beast’) appeared in Early Miocene North America and crossed the Bering Strait to Asia and Europe. Later in the Miocene, in North America a new type of horse appeared that took advantage of the grasslands, Merychippus (‘ruminant horse’). During the Pliocene (‘more new’ life) the near modern Pliohippus (‘more horse’) appeared in North America. The close of the Pliocene in North America saw the rise of the first modern horses of the genus Equus (‘horse’) – basically a larger, longer-legged version of Pliohippus.
The artiodactyls were now at their most successful. Anthracotheres (‘coal beasts’) – the first fossils were found in coal beds in France – were aquatic, pig-like animals that probably filled an ecological niche of the modern hippopotamus.
Bovoid evolution began in the Early Miocene with the appearance of Eotragus in Africa, Europe and Mongolia. By the end of the Miocene over seventy genera had appeared. During the Pleistocene bovoids migrated into North America where they founded populations of bighorn sheep, bison, mountain goat, and musk ox.
The early evolution of elephants apparently took place in Africa. Moeritherium (‘Lake Moeris + beast’) had the proportions of a long-bodied pig, and may have lived an amphibious life like a small hippopotamus. Related to Moeritherium were the deinotheres (‘terrible beasts’). Deinotherium giganteum may have stood four metres (13 ft) at the shoulder. More conventional early elephants were the mastodons (‘nipple teeth’), represented by creatures such as Phiomia (‘Faiyum’). True elephants and mammoths arose from animals not unlike Gomphotherium (‘welded beast’). There were three lines. One led to the African elephant, the second led to the Indian elephant and the third comprised the mammoths.
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