The Miocene epoch spans the geological period from around 23 million to roughly 5 million years ago within the Neogene period. The Miocene represents a transitional bridge between primitive ecosystems of the Early Cenozoic towards the modern biomes of today and the later emergence of human ancestors.
- Climate & Environments: Miocene climates shifted from warm and humid conditions early towards drier, more seasonal grassland habitats later, prompting ecological transitions from forests to open woodlands and grassy biomes.
- Flora & Fauna: Miocene terrestrial faunas included early equids, camelids, and antelope coexisting with remnants of mammoth-like mastodonts, giant birds, and large sabertooth cats. Grassland expansion supported grazing herds.
- Marine Life: Oceans hosted marine mammals like baleen whales, seals, and sea cows alongside prolific mollusk diversity. Reef ecosystems approached modern coral assemblages.
- Hominins: Miocene vegetation supported the divergence of great ape ancestors and early hominoid lineages that eventually gave rise to modern humans millions of years later.
In general, the rich Miocene biodiversity, grassland radiations, and hominoid evolutionary developments paved the foundation for Pliocene ecosystems and modern fauna more recognizable today. These events unfolded alongside shifting tectonics, sea levels, and climate fluctuations during the dynamic Miocene epoch.
The warm, wet climates prevailing across much of the Miocene enabled prolific jungle and woodland environments where early primate evolution thrived. South American forests hosted an incredible diversity of mammalian megaherbivore species at ten times modern levels, including giant sloths, armored glyptodonts, and hippo-like toxodonts alongside nimble primate radiations.
In Africa, Miocene fossil beds reveal ancestries spanning apes, early hunter-forager hominins like Sahelanthropus, and emerging tool-using behaviors. Meanwhile, Eurasian fossil assemblages exhibit transitions where mastodont predecessors to modern elephants with shorter tusks and longer legs adapted to more open, seasonal habitats.
Shifting ocean currents and seaways facilitated new marine colonization as Atlantic waters reconnected to the Mediterranean Sea during the "Messinian salinity crisis". Following massive floods refilling this basin, creatures redistributed across western oceans. Miocene mollusk fossil beds contain species counted in the thousands.
While early Miocene ecosystems contained remnants of dinosaurs and giant land mammals from prior epochs, late Miocene faunal turnovers show specialization towards faster ungulates grazed on expanding grasslands and sabercats preying on proliferating antelope, deer, horse, and camel lineages. Ancestral dogs, bears, rhinos, and apes also thrived in woodland fringes.
In summary, dynamic Miocene climates, habitats and connections sparked newly evolving ecological richness while setting the stage for Pliocene patterns that ultimately gave way to familiar modern ecosystems. The Miocene nourished globally prolific biodiversity.
The Miocene epoch featured striking adaptive radiations among early horse lineages native to North America as they diversified from small multi-toed forest browsers towards sleeker grazers with elongated limbs and single hooves - epitomized by the 15 million-year-old Merychippus. This adaptation to roaming grasslands predated modern Equus horse species.
Prolific ape speciation events also occurred across Africa and Eurasia alongside the evolution of hybrid hominoid genera such as Dryopithecus - considered a candidate ancestor genus containing divergent gorilla, orangutan, and early hominin split-offs. Varied diets and locomotion patterns defined myriad Miocene apes and monkeys before extinction pruned lineages.
Emerging grassy biomes supported massive herd megaherbivores like the peculiar-looking Chalicotheres that occupied ecological niches akin to modern rhinoceros but bearing clawed feet and knuckle-walking gorilla-like. These extinct families represent just a snippet of Miocene faunal diversity.
Intriguing Miocene marine fossils also reveal transient whale forms in transition exhibiting vestigial hip and leg bones not seen in fully aquatic modern cetaceans. These amphibious intermediaries highlight four-legged mammals returning to ocean environments in stages.
In essence, the Miocene signified a proliferation phase as mammals explored specialist offshoots across newly opening niches thanks to favorable conditions and habitats. Though many Miocene experimental branches ultimately pruned away, they left a legacy still evident across today's range of modern fauna.