Life during the Miocene Epoch was mostly supported by the two newly formed biomes, kelp forests and grasslands. This allows for more grazers, such as horses, rhinoceroses,and hippos. Ninety five percent of modern plants existed by the end of this epoch. The coevolution of gritty, fibrous, fire-tolerant grasses and long-legged gregarious ungulates with high-crowned teeth, led to a major expansion of grass-grazer ecosystems, with roaming herds of large, swift grazers pursued by predators across broad sweeps of open grasslands, displacing desert, woodland, and browsers.
The higher organic content and water retention of the deeper and richer grassland soils, with long term burial of carbon in sediments, produced a carbon and water vapor sink.
This, combined with higher surface albedo and lower evapotranspiration of grassland, contributed to a cooler, drier climate. C4 grasses, which are able to assimilate carbon dioxide and water more efficiently than C3 grasses, expanded to become ecologically significant near the end of the Miocene between 6 and 7 million years ago. The expansion of grasslands and radiations among terrestrial herbivores correlates to fluctuations in CO2.
Cycads between Both marine and continental fauna were fairly modern, although marine mammals were less numerous. Only in isolated South America and Australia did widely divergent fauna exist. In the Early Miocene, several Oligocene groups were still diverse, including nimravids, entelodonts, and three-toed horses. Like in the previous Oligocene epoch, oreodonts were still diverse, only to disappear in the earliest Pliocene.
During the later Miocene mammals were more modern, with easily recognizable dogs, bears, raccoons, horses, beaver, deer, camels, and whales, along with now extinct groups like borophagine dogs, gomphotheres, three-toed horses, and semi-aquatic and hornless rhinos like Teleoceras and Aphelops. The expansion of silica-rich C4 grasses led to worldwide extinctions of herbivorous species without high-crowned teeth.
Unequivocally recognizable dabbling ducks, plovers, typical owls, cockatoos and crows appear during the Miocene. Marine birds reached their highest diversity ever in the course of this epoch. Approximately species of apes lived during this time. They ranged over much of the Old World and varied widely in size, diet, and anatomy.
Due to scanty fossil evidence it is unclear which ape or apes contributed to the modern hominid clade, but molecular evidence indicates this ape lived from between 15 to 12 million years ago. In the oceans, brown algae, called kelp, proliferated, supporting new species of sea life, including otters, fish and various invertebrates.
Cetaceans attained their greatest diversity during the Miocene, with over 20 recognized genera in comparison to only six living genera.
This diversification correlates with emergence of gigantic macro-predators such as megatoothed sharks and raptorial sperm whales. Prominent examples are C.
Other notable large sharks were C. Crocodilians also showed signs of diversification during Miocene. The largest form among them was a gigantic caiman Purussaurus which inhabited South America. Another gigantic form was a false gharial Rhamphosuchus, which inhabited modern age India. A strange form Mourasuchus also thrived alongside Purussaurus. This species developed a specialized filter-feeding mechanism, and it likely preyed upon small fauna despite its gigantic size. The pinnipeds, which appeared near the end of the Oligocene, became more aquatic.
Prominent genus was Allodesmus. Extensive mountain building in the Americas and Asia alters air circulation and weather patterns, contributing to drier overall conditions. Antarctica's separation from South America during the Oligocene, however, inhibits the mixing of warm, tropical waters with cool, polar waters. Antarctica freezes, and global climate cools again. Marine mammals like seals and whales flourish as deep, nutrient-rich waters are stirred up in the process. Land bridges, which form as the oceans recede and as inland waters dry out, encourage new waves of animal migration between continents.
In the cooler, drier conditions, grasslands begin to dominate the Americas and eastern Eurasia. Grassland habitats offer plenty of food for evolving grazers, including deer and antelope. Horses, which first appeared in the Eocene, grow considerably larger, and some now display a single toe on each limb instead of three or four. Animals that do not adapt to the more severe climate and coarser vegetation, such as giant camels, which feed on leafy trees much like a giraffe, teeter on the verge of extinction.
The Miocene begins with a gradual, short-lived warming, and some tropical forests expand. Drying accompanies this temperature change, and tough scrub plants evolve as a new form of vegetation. Where continental plates collide, Earth's crust is lifted. These massive formations disrupt wind and weather patterns, altering rainfall distribution. As newly exposed rock surfaces weather, carbon dioxide is removed from the atmosphere. This might contribute to global cooling. Communities of large brown algae, called kelp, support evolving marine life, such as sea otters, as well as established groups of fishes and invertebrates.
Though kelp is a plant, it is not closely related to its land counterparts. For one thing, its cells use different pigments for photosynthesis. Kelp grows in cool, shallow waters, where it attaches to rocks and coral or sometimes floats freely. Because marine plants do not preserve well over time, scientists can date kelp only to the Miocene, when animals it supports are known to appear, but it may exist in earlier periods.
The shifting continents, changing climate patterns, and formation of a polar ice cap cause sea levels to drop and inland seas to shrink. Land routes open between continents, most notably between Africa and Eurasia, and Eurasia and North America. Well studied continental exposures occur in the American Great Plains and in Argentina. India continued to collide with Asia, creating more mountain ranges.
Tethys Seaway continued to shrink. Miocene flora Grasslands underwent a major expansion as forests fell victim to a generally cooler and drier climate overall. Grasses also diversified greatly into a number of species and also caused a major increase in the biodiversity of large herbivores and grazers, including ruminants of which modern cattle and deer belong.
Miocene fauna Both marine and continental fauna were fairly modern, although marine mammals were less numerous. Only in isolated South America and Australia did widely divergent fauna exist. Mammals These were also modern, with recognizable wolves, raccoons, horses , beaver , deer, camels , and whales. Birds Recognizable crows , ducks, auks, grouses and owls appear in the Miocene.
By the epoch's end, all or almost all modern families are believed to have been present; the few post-Miocene bird fossils which cannot be placed in the evolutionary tree with full confidence are simply too badly preserved instead of too equivocal in character.
Marine birds reached their highest diversity ever in the course of this epoch.
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