Miocene Proboscideans
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The Miocene ( ) is the first geological epoch of the
Neogene The Neogene ( ), informally Upper Tertiary or Late Tertiary, is a geologic period and system that spans 20.45 million years from the end of the Paleogene Period million years ago ( Mya) to the beginning of the present Quaternary Period Mya. ...
Period and extends from about (Ma). The Miocene was named by Scottish geologist
Charles Lyell Sir Charles Lyell, 1st Baronet, (14 November 1797 – 22 February 1875) was a Scottish geologist who demonstrated the power of known natural causes in explaining the earth's history. He is best known as the author of ''Principles of Geolo ...
; the name comes from the Greek words (', "less") and (', "new") and means "less recent" because it has 18% fewer modern marine invertebrates than the
Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58Oligocene The Oligocene ( ) is a geologic epoch of the Paleogene Period and extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that define the epoch are well identified but t ...
and is followed by the
Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58ice age An ice age is a long period of reduction in the temperature of Earth's surface and atmosphere, resulting in the presence or expansion of continental and polar ice sheets and alpine glaciers. Earth's climate alternates between ice ages and gre ...
s. The Miocene boundaries are not marked by a single distinct global event but consist rather of regionally defined boundaries between the warmer Oligocene and the cooler Pliocene Epoch. During the Early Miocene, the
Arabian Peninsula The Arabian Peninsula, (; ar, شِبْهُ الْجَزِيرَةِ الْعَرَبِيَّة, , "Arabian Peninsula" or , , "Island of the Arabs") or Arabia, is a peninsula of Western Asia, situated northeast of Africa on the Arabian Plat ...
collided with Eurasia, severing the connection between the Mediterranean and Indian Ocean, and allowing a faunal interchange to occur between Eurasia and Africa, including the dispersal of
proboscidea The Proboscidea (; , ) are a taxonomic order of afrotherian mammals containing one living family ( Elephantidae) and several extinct families. First described by J. Illiger in 1811, it encompasses the elephants and their close relatives. Fr ...
ns into Eurasia. During the late Miocene, the connections between the Atlantic and Mediterranean closed, causing the Mediterranean Sea to nearly completely evaporate, in an event called the
Messinian salinity crisis The Messinian salinity crisis (MSC), also referred to as the Messinian event, and in its latest stage as the Lago Mare event, was a geological event during which the Mediterranean Sea went into a cycle of partial or nearly complete desiccation (d ...
. The
Strait of Gibraltar The Strait of Gibraltar ( ar, مضيق جبل طارق, Maḍīq Jabal Ṭāriq; es, Estrecho de Gibraltar, Archaic: Pillars of Hercules), also known as the Straits of Gibraltar, is a narrow strait that connects the Atlantic Ocean to the Medi ...
opened and the Mediterranean refilled at the Miocene–Pliocene boundary, in an event called the Zanclean flood. The apes first evolved, arose, and diversified during the
early Miocene The Early Miocene (also known as Lower Miocene) is a sub-epoch of the Miocene epoch (geology), Epoch made up of two faunal stage, stages: the Aquitanian age, Aquitanian and Burdigalian stages. The sub-epoch lasted from 23.03 ± 0.05 annum, Ma to ...
(Aquitanian and Burdigalian Stages), becoming widespread in the
Old World The "Old World" is a term for Afro-Eurasia that originated in Europe , after Europeans became aware of the existence of the Americas. It is used to contrast the continents of Africa, Europe, and Asia, which were previously thought of by thei ...
. By the end of this epoch and the start of the following one, the ancestors of humans had split away from the ancestors of the
chimpanzee The chimpanzee (''Pan troglodytes''), also known as simply the chimp, is a species of great ape native to the forest and savannah of tropical Africa. It has four confirmed subspecies and a fifth proposed subspecies. When its close relative t ...
s to follow their own evolutionary path during the final Messinian Stage (7.5–5.3 Ma) of the Miocene. As in the Oligocene before it,
grassland A grassland is an area where the vegetation is dominated by grasses ( Poaceae). However, sedge ( Cyperaceae) and rush ( Juncaceae) can also be found along with variable proportions of legumes, like clover, and other herbs. Grasslands occur na ...
s continued to expand and forests to dwindle in extent. In the seas of the Miocene, kelp forests made their first appearance and soon became one of Earth's most productive ecosystems. The plants and animals of the Miocene were recognizably modern. Mammals and birds were well-established.
Whale Whales are a widely distributed and diverse group of fully aquatic placental marine mammals. As an informal and colloquial grouping, they correspond to large members of the infraorder Cetacea, i.e. all cetaceans apart from dolphins and ...
s,
pinniped Pinnipeds (pronounced ), commonly known as seals, are a widely distributed and diverse clade of carnivorous, fin-footed, semiaquatic, mostly marine mammals. They comprise the extant families Odobenidae (whose only living member is the ...
s, and
kelp Kelps are large brown algae seaweeds that make up the order Laminariales. There are about 30 different genera. Despite its appearance, kelp is not a plant - it is a heterokont, a completely unrelated group of organisms. Kelp grows in "underwa ...
spread. The Miocene is of particular interest to geologists and palaeoclimatologists as major phases of the geology of the Himalaya occurred during the Miocene, affecting
monsoon A monsoon () is traditionally a seasonal reversing wind accompanied by corresponding changes in precipitation but is now used to describe seasonal changes in atmospheric circulation and precipitation associated with annual latitudinal oscil ...
al patterns in Asia, which were interlinked with glacial periods in the northern hemisphere.


Subdivisions

The Miocene faunal stages from youngest to oldest are typically named according to the
International Commission on Stratigraphy The International Commission on Stratigraphy (ICS), sometimes referred to unofficially as the "International Stratigraphic Commission", is a daughter or major subcommittee grade scientific daughter organization that concerns itself with stratigr ...
: Regionally, other systems are used, based on characteristic land mammals; some of them overlap with the preceding Oligocene and following Pliocene Epochs: European Land Mammal Ages *
Turolian The Turolian age is a period of geologic time The geologic time scale, or geological time scale, (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the pr ...
(9.0 to 5.3 Ma) *
Vallesian The Vallesian age is a period of geologic time (11.6–9.0 Ma) within the Miocene used more specifically with European Land Mammal Ages. It precedes the Turolian age and follows the Astaracian age. The so-called Vallesian Crisis resulted in the ...
(11.6 to 9.0 Ma) * Astaracian (16.0 to 11.6 Ma) *
Orleanian The Orleanian age is a period of geologic time ( MN 3–5, (mya)), within the Miocene and used more specifically with European Land Mammal Ages. It precedes the Astaracian age and follows the Agenian age. ; Agenian-Early Orleanian migration At t ...
(20.0 to 16.0 Ma) * Agenian (23.8 to 20.0 Ma) North American Land Mammal Ages * Hemphillian (10.3 to 4.9 Ma) *
Clarendonian The Clarendonian North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), typically set from 13,600,000 to 10,300,000 years BP, a period of . It is ...
(13.6 to 10.3 Ma) *
Barstovian The Barstovian North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), typically set from 16,300,000 to 13,600,000 years BP, a period of . It is u ...
(16.3 to 13.6 Ma) * Hemingfordian (20.6 to 16.3 Ma) * Arikareean (30.6 to 20.6 Ma) South American Land Mammal Ages * Montehermosan (6.8 to 4.0 Ma) *
Huayquerian The Huayquerian ( es, Huayqueriense) age is a period of geologic time (9.0–6.8 Ma) within the Late Miocene epoch of the Neogene, used more specifically within the SALMA classification. It follows the Mayoan The Mayoan ( es, Mayoense) age is a ...
(9.0 to 6.8 Ma) * Mayoan (11.8 to 9.0 Ma) * Laventan (13.8 to 11.8 Ma) *
Colloncuran The Colloncuran ( es, Colloncurense) age is a period of geologic time (15.5–13.8 Ma) within the Middle Miocene epoch of the Neogene, used more specifically within the SALMA classification in South America. It follows the Friasian and precedes ...
(15.5 to 13.8 Ma) *
Friasian The Friasian age is a period of geologic time (16.3–15.5 Ma) within the Early Miocene epoch of the Neogene, used more specifically within the SALMA classification of South America. It follows the Santacrucian and precedes the Colloncuran age. ...
(16.3 to 15.5 Ma) *
Santacrucian The Santacrucian age is a period of geologic time (17.5 – 16.3 Mya (unit), Ma) within the Early Miocene epoch of the Neogene, used more specifically with South American land mammal age, SALMA classification in South America. It follows the Colhue ...
(17.5 to 16.3 Ma) *
Colhuehuapian The Colhuehuapian age is a period of geologic time (21.0–17.5 Ma) within the Early Miocene epoch of the Neogene, used more specifically within the SALMA classification in South America. It follows the Deseadan and precedes the Santacrucian age. ...
(21.0 to 17.5 Ma)


Paleogeography

Continents continued to
drift Drift or Drifts may refer to: Geography * Drift or ford (crossing) of a river * Drift, Kentucky, unincorporated community in the United States * In Cornwall, England: ** Drift, Cornwall, village ** Drift Reservoir, associated with the village ...
toward their present positions. Of the modern geologic features, only the land bridge between
South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the sou ...
and
North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and th ...
was absent, although South America was approaching the western
subduction zone Subduction is a geological process in which the oceanic lithosphere is recycled into the Earth's mantle at convergent boundaries. Where the oceanic lithosphere of a tectonic plate converges with the less dense lithosphere of a second plate, the ...
in the
Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the conti ...
, causing both the rise of the
Andes The Andes, Andes Mountains or Andean Mountains (; ) are the longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range is long, wide (widest between 18°S – 20°S ...
and a southward extension of the Meso-American peninsula. Mountain building took place in western
North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and th ...
,
Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...
, and
East Asia East Asia is the eastern region of Asia, which is defined in both geographical and ethno-cultural terms. The modern states of East Asia include China, Japan, Mongolia, North Korea, South Korea, and Taiwan. China, North Korea, South Korea ...
. Both continental and marine Miocene deposits are common worldwide with marine outcrops common near modern shorelines. Well studied continental exposures occur in the North American
Great Plains The Great Plains (french: Grandes Plaines), sometimes simply "the Plains", is a broad expanse of flatland in North America. It is located west of the Mississippi River and east of the Rocky Mountains, much of it covered in prairie, steppe, a ...
and in
Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the List of South American countries by area, second-largest ...
. The global trend was towards increasing aridity caused primarily by global cooling reducing the ability of the atmosphere to absorb moisture, particularly after 7 to 8 million years ago. Uplift of
East Africa East Africa, Eastern Africa, or East of Africa, is the eastern subregion of the African continent. In the United Nations Statistics Division scheme of geographic regions, 10-11-(16*) territories make up Eastern Africa: Due to the historica ...
in the late Miocene was partly responsible for the shrinking of
tropical rain forest Tropical rainforests are rainforests that occur in areas of tropical rainforest climate in which there is no dry season – all months have an average precipitation of at least 60 mm – and may also be referred to as ''lowland equatori ...
s in that region, and
Australia Australia, officially the Commonwealth of Australia, is a sovereign country comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands. With an area of , Australia is the largest country by ...
got drier as it entered a zone of low rainfall in the Late Miocene.


Eurasia

India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area, the List of countries and dependencies by population, second-most populous ...
continued to collide with
Asia Asia (, ) is one of the world's most notable geographical regions, which is either considered a continent in its own right or a subcontinent of Eurasia, which shares the continental landmass of Afro-Eurasia with Africa. Asia covers an are ...
, creating dramatic new
mountain range A mountain range or hill range is a series of mountains or hills arranged in a line and connected by high ground. A mountain system or mountain belt is a group of mountain ranges with similarity in form, structure, and alignment that have ari ...
s as well as uplifting the Tibetan Plateau, which resulted in the aridification of the Asian interior. At the beginning of the Miocene, the northern margin of the Arabian plate, then part of the African landmass, collided with Eurasia; as a result, the Tethys seaway continued to shrink and then disappeared as
Africa Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...
collided with
Eurasia Eurasia (, ) is the largest continental area on Earth, comprising all of Europe and Asia. Primarily in the Northern and Eastern Hemispheres, it spans from the British Isles and the Iberian Peninsula in the west to the Japanese archipelag ...
in the Turkish
Arabian The Arabian Peninsula, (; ar, شِبْهُ الْجَزِيرَةِ الْعَرَبِيَّة, , "Arabian Peninsula" or , , "Island of the Arabs") or Arabia, is a peninsula of Western Asia, situated northeast of Africa on the Arabian Plat ...
region between 19 and 12 Ma. This severed the connection between the Indian Ocean and the Mediterranean Sea and formed the present land connection between Afro-Arabia and Eurasia. The subsequent uplift of mountains in the western
Mediterranean The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western and Southern Europe and Anatolia, on the south by North Africa, and on ...
region and a global fall in sea levels combined to cause a temporary drying up of the Mediterranean Sea (known as the
Messinian salinity crisis The Messinian salinity crisis (MSC), also referred to as the Messinian event, and in its latest stage as the Lago Mare event, was a geological event during which the Mediterranean Sea went into a cycle of partial or nearly complete desiccation (d ...
) near the end of the Miocene.


South America

During the
Oligocene The Oligocene ( ) is a geologic epoch of the Paleogene Period and extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that define the epoch are well identified but t ...
and Early Miocene, the coast of northern Brazil, Colombia, south-central Peru, central Chile and large swathes of inland
Patagonia Patagonia () refers to a geographical region that encompasses the southern end of South America, governed by Argentina and Chile. The region comprises the southern section of the Andes Mountains with lakes, fjords, temperate rainforests, and g ...
were subject to a
marine transgression A marine transgression is a geologic event during which sea level rises relative to the land and the shoreline moves toward higher ground, which results in flooding. Transgressions can be caused by the land sinking or by the ocean basins filling ...
. The transgressions in the west coast of South America are thought to be caused by a regional phenomenon while the steadily rising central segment of the Andes represents an exception. While there are numerous registers of Oligo-Miocene transgressions around the world it is doubtful that these correlate. It is thought that the Oligo-Miocene transgression in
Patagonia Patagonia () refers to a geographical region that encompasses the southern end of South America, governed by Argentina and Chile. The region comprises the southern section of the Andes Mountains with lakes, fjords, temperate rainforests, and g ...
could have temporarily linked the Pacific and Atlantic Oceans, as inferred from the findings of marine invertebrate fossils of both Atlantic and Pacific affinity in
La Cascada Formation La Cascada Formation a sedimentary formation near Futaleufú in the western Patagonian Andes of southern Chile. Lithologies vary from sandstone, siltstone and conglomerate. The sediment that now forms the rock deposited during the Oligocene and ...
. Connection would have occurred through narrow epicontinental seaways that formed channels in a dissected topography. The
Antarctic Plate The Antarctic Plate is a tectonic plate containing the continent of Antarctica, the Kerguelen Plateau, and some remote islands in the Southern Ocean and other surrounding oceans. After breakup from Gondwana (the southern part of the superconti ...
started to subduct beneath South America 14 million years ago in the Miocene, forming the
Chile Triple Junction The Chile Triple Junction (or Chile Margin Triple Junction) is a geologic triple junction located on the seafloor of the Pacific Ocean off Taitao and Tres Montes Peninsula on the southern coast of Chile. Here three tectonic plates meet: the South ...
. At first the Antarctic Plate subducted only in the southernmost tip of Patagonia, meaning that the Chile Triple Junction lay near the
Strait of Magellan The Strait of Magellan (), also called the Straits of Magellan, is a navigable sea route in southern Chile separating mainland South America to the north and Tierra del Fuego to the south. The strait is considered the most important natural ...
. As the southern part of
Nazca Plate The Nazca Plate or Nasca Plate, named after the Nazca region of southern Peru, is an oceanic tectonic plate in the eastern Pacific Ocean basin off the west coast of South America. The ongoing subduction, along the Peru–Chile Trench, of the N ...
and the
Chile Rise The Chile Ridge, also known as the Chile Rise, is a submarine oceanic ridge formed by the divergent plate boundary between the Nazca Plate and the Antarctic Plate. It extends from the triple junction of the Nazca, Pacific, and Antarctic plates ...
became consumed by subduction the more northerly regions of the Antarctic Plate begun to subduct beneath Patagonia so that the Chile Triple Junction advanced to the north over time. The asthenospheric window associated to the triple junction disturbed previous patterns of
mantle convection Mantle convection is the very slow creeping motion of Earth's solid silicate mantle as convection currents carrying heat from the interior to the planet's surface. The Earth's surface lithosphere rides atop the asthenosphere and the two form ...
beneath Patagonia inducing an uplift of ca. 1 km that reversed the Oligocene–Miocene transgression. As the southern Andes rose in the Middle Miocene (14–12 million years ago) the resulting
rain shadow A rain shadow is an area of significantly reduced rainfall behind a mountainous region, on the side facing away from prevailing winds, known as its leeward side. Evaporated moisture from water bodies (such as oceans and large lakes) is ca ...
originated the Patagonian Desert to the east.


Climate

Climates remained moderately warm, although the slow global cooling that eventually led to the
Pleistocene The Pleistocene ( , often referred to as the ''Ice age'') is the geological Epoch (geology), epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fina ...
glaciation A glacial period (alternatively glacial or glaciation) is an interval of time (thousands of years) within an ice age that is marked by colder temperatures and glacier advances. Interglacials, on the other hand, are periods of warmer climate bet ...
s continued. Although a long-term cooling trend was well underway, there is evidence of a warm period during the Miocene when the global climate rivalled that of the
Oligocene The Oligocene ( ) is a geologic epoch of the Paleogene Period and extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that define the epoch are well identified but t ...
. The Miocene warming began 21 million years ago and continued until 14 million years ago, when global temperatures took a sharp drop—the
Middle Miocene Climate Transition The term Middle Miocene disruption, alternatively the Middle Miocene extinction or Middle Miocene extinction peak, refers to a wave of extinctions of terrestrial and aquatic life forms that occurred around the middle of the Miocene, roughly 14 mill ...
(MMCT). By 7 to 8 million years ago, temperatures dropped sharply once again, most likely as a result of a decline in atmospheric carbon dioxide and a drop in the amplitude of Earth's obliquity, and the
Antarctic ice sheet The Antarctic ice sheet is one of the two polar ice caps of Earth. It covers about 98% of the Antarctic continent and is the largest single mass of ice on Earth, with an average thickness of over 2 kilometers. It covers an area of almost and ...
was already approaching its present-day size and thickness.
Greenland Greenland ( kl, Kalaallit Nunaat, ; da, Grønland, ) is an island country in North America that is part of the Kingdom of Denmark. It is located between the Arctic and Atlantic oceans, east of the Canadian Arctic Archipelago. Greenland ...
may have begun to have large glaciers as early as 7 to 8 million years ago, although the climate for the most part remained warm enough to support forests there well into the Pliocene. At the terminus of the Miocene, global temperatures rose once again as the amplitude of Earth's obliquity increased.


Life

Life during the Miocene Epoch was mostly supported by the two newly formed
biome A biome () is a biogeographical unit consisting of a biological community that has formed in response to the physical environment in which they are found and a shared regional climate. Biomes may span more than one continent. Biome is a broader ...
s, kelp forests and grasslands. Grasslands allow for more grazers, such as
horse The horse (''Equus ferus caballus'') is a domesticated, one-toed, hoofed mammal. It belongs to the taxonomic family Equidae and is one of two extant subspecies of ''Equus ferus''. The horse has evolved over the past 45 to 55 million yea ...
s,
rhinoceros A rhinoceros (; ; ), commonly abbreviated to rhino, is a member of any of the five extant species (or numerous extinct species) of odd-toed ungulates in the family Rhinocerotidae. (It can also refer to a member of any of the extinct specie ...
es, and hippos. Ninety-five percent of modern plants existed by the end of this epoch. Modern bony fish genera were established.


Flora

The
coevolution In biology, coevolution occurs when two or more species reciprocally affect each other's evolution through the process of natural selection. The term sometimes is used for two traits in the same species affecting each other's evolution, as well ...
of gritty, fibrous, fire-tolerant
grasses Poaceae () or Gramineae () is a large and nearly ubiquitous family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos and the grasses of natural grassland and species cultivated in lawns ...
and long-legged gregarious
ungulate Ungulates ( ) are members of the diverse clade Ungulata which primarily consists of large mammals with hooves. These include odd-toed ungulates such as horses, rhinoceroses, and tapirs; and even-toed ungulates such as cattle, pigs, giraffes, ...
s with high-crowned teeth, led to a major expansion of grass-grazer ecosystems, with roaming herds of large,
swift Swift or SWIFT most commonly refers to: * SWIFT, an international organization facilitating transactions between banks ** SWIFT code * Swift (programming language) * Swift (bird), a family of birds It may also refer to: Organizations * SWIFT, ...
grazers pursued by predators across broad sweeps of open
grassland A grassland is an area where the vegetation is dominated by grasses ( Poaceae). However, sedge ( Cyperaceae) and rush ( Juncaceae) can also be found along with variable proportions of legumes, like clover, and other herbs. Grasslands occur na ...
s, 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 Albedo (; ) is the measure of the diffuse reflection of solar radiation out of the total solar radiation and measured on a scale from 0, corresponding to a black body that absorbs all incident radiation, to 1, corresponding to a body that refle ...
and lower
evapotranspiration Evapotranspiration (ET) is the combined processes by which water moves from the earth’s surface into the atmosphere. It covers both water evaporation (movement of water to the air directly from soil, canopies, and water bodies) and transp ...
of grassland, contributed to a cooler, drier climate. C4 grasses, which are able to assimilate
carbon dioxide Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is t ...
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.
Cycad Cycads are seed plants that typically have a stout and woody (ligneous) trunk with a crown of large, hard, stiff, evergreen and (usually) pinnate leaves. The species are dioecious, that is, individual plants of a species are either male o ...
s between 11.5 and 5 million years ago began to rediversify after previous declines in variety due to climatic changes, and thus modern cycads are not a good model for a "living fossil".
Eucalyptus ''Eucalyptus'' () is a genus of over seven hundred species of flowering trees, shrubs or mallees in the myrtle family, Myrtaceae. Along with several other genera in the tribe Eucalypteae, including '' Corymbia'', they are commonly known as ...
fossil leaves occur in the Miocene of
New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island coun ...
, where the genus is not native today, but have been introduced from
Australia Australia, officially the Commonwealth of Australia, is a sovereign country comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands. With an area of , Australia is the largest country by ...
.


Fauna

Both marine and continental
fauna Fauna is all of the animal life present in a particular region or time. The corresponding term for plants is '' flora'', and for fungi, it is '' funga''. Flora, fauna, funga and other forms of life are collectively referred to as '' biota''. ...
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 equids. 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 canids,
bear Bears are carnivoran mammals of the family Ursidae. They are classified as caniforms, or doglike carnivorans. Although only eight species of bears are extant, they are widespread, appearing in a wide variety of habitats throughout the No ...
s,
red pandas The red panda (''Ailurus fulgens''), also known as the lesser panda, is a small mammal native to the eastern Himalayas and southwestern China. It has dense reddish-brown fur with a black belly and legs, white-lined ears, a mostly white muzzle ...
,
procyonids Procyonidae is a New World family of the order Carnivora. It comprises the raccoons, ringtails, cacomistles, coatis, kinkajous, olingos, and olinguitos. Procyonids inhabit a wide range of environments and are generally omnivorous. Characteri ...
,
equids Equidae (sometimes known as the horse family) is the taxonomic family of horses and related animals, including the extant horses, asses, and zebras, and many other species known only from fossils. All extant species are in the genus '' Equus' ...
,
beaver Beavers are large, semiaquatic rodents in the genus ''Castor'' native to the temperate Northern Hemisphere. There are two extant species: the North American beaver (''Castor canadensis'') and the Eurasian beaver (''C. fiber''). Beavers a ...
s,
deer Deer or true deer are hoofed ruminant mammals forming the family Cervidae. The two main groups of deer are the Cervinae, including the muntjac, the elk (wapiti), the red deer, and the fallow deer; and the Capreolinae, including the re ...
, camelids, and
whale Whales are a widely distributed and diverse group of fully aquatic placental marine mammals. As an informal and colloquial grouping, they correspond to large members of the infraorder Cetacea, i.e. all cetaceans apart from dolphins and ...
s, along with now extinct groups like borophagine canids, certain
gomphothere Gomphotheres are any members of the diverse, extinct taxonomic family Gomphotheriidae. Gomphotheres were elephant-like proboscideans, but do not belong to the family Elephantidae. They were widespread across Afro-Eurasia and North America dur ...
s, three-toed horses, and hornless rhinos like '' Teleoceras'' and '' Aphelops''. Islands began to form between South and North America in the Late Miocene, allowing ground sloths like '' Thinobadistes'' to island-hop to North America. The expansion of silica-rich C4 grasses led to worldwide extinctions of herbivorous species without high-crowned teeth. Mustelids diversified into their largest forms as terrestrial predators like '' Ekorus'', ''
Eomellivora ''Eomellivora'' is an extinct genus of prehistoric mustelids, closely related to the honey badger, known from Eurasia and North America, and tentatively Africa. It was one of the biggest mustelids ever known, bigger and more hypercarnivorous than ...
'', and ''
Megalictis ''Megalictis'' is an extinct genus of large predatory mustelids that existed in North America during the " cat gap" from the Late Arikareean (Ar4) in the Miocene epoch. It is thought to have resembled a huge ferret, with a body mass of up to . H ...
'' and bunodont otters like '' Enhydriodon'' and ''Sivaonyx'' appeared. Unequivocally recognizable
dabbling duck The Anatinae are a subfamily of the family Anatidae (swans, geese and ducks). Its surviving members are the dabbling ducks, which feed mainly at the surface rather than by diving. The other members of the Anatinae are the extinct moa-nalo, a yo ...
s,
plover Plovers ( , ) are a widely distributed group of wading birds belonging to the subfamily Charadriinae. Description There are about 66 species in the subfamily, most of them called "plover" or "dotterel". The closely related lapwing subf ...
s,
typical owl The true owls or typical owls (family Strigidae) are one of the two generally accepted families of owls, the other being the barn owls (Tytonidae). This large family comprises 230 living or recently extinct species in 24 genera. The typical ow ...
s, cockatoos and
crow A crow is a bird of the genus '' Corvus'', or more broadly a synonym for all of ''Corvus''. Crows are generally black in colour. The word "crow" is used as part of the common name of many species. The related term "raven" is not pinned scientifica ...
s appear during the Miocene. By the epoch's end, all or almost all modern bird groups 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, rather than too equivocal in character. Marine birds reached their highest diversity ever in the course of this epoch. The youngest representatives of
Choristodera Choristodera (from the Greek χωριστός ''chōristos'' + δέρη ''dérē'', 'separated neck') is an extinct order of semiaquatic diapsid reptiles that ranged from the Middle Jurassic, or possibly Triassic, to the late Miocene (168 to ...
, an extinct order of aquatic reptiles that first appeared in the
Middle Jurassic The Middle Jurassic is the second Epoch (geology), epoch of the Jurassic Period (geology), Period. It lasted from about 174.1 to 163.5 million years ago. Fossils of land-dwelling animals, such as dinosaurs, from the Middle Jurassic are relatively ...
, are known from the Miocene of Europe, belonging to the genus '' Lazarussuchus,'' which had been the only known surviving genus of the group since the beginning of the Eocene. The last known representatives of the archaic primitive mammal order
Meridiolestida Meridiolestida is an extinct clade of mammals known from the Cretaceous and Cenozoic of South America and possibly Antarctica. They represented the dominant group of mammals in South America during the Late Cretaceous. Meridiolestidans were morph ...
, which dominated South America during the Late Cretaceous, are known from the Miocene of Patagonia, represented by the mole-like '' Necrolestes.'' The youngest known representatives of metatherians (marsupial relatives) in the Northern Hemisphere landmasses (Asia, North America and Europe) and Africa are known from the Miocene, including the North American herpetotheriid ''
Herpetotherium ''Herpetotherium'' is an extinct genus of metatherian mammal, belonging to the possibly paraphyletic family Herpetotheriidae. Native to North America from the Eocene to Early Miocene, fossils have been found in California, Oregon, Texas, Florida ...
'', the European herpetotheriid '' Amphiperatherium,'' the peradectids '' Siamoperadectes'' and '' Sinoperadectes'' from Asia, and the possible herpetotheriid '' Morotodon'' from the late Early Miocene of Uganda. Approximately 100 species of apes lived during this time, ranging throughout Africa, Asia and Europe and varying widely in size, diet, and anatomy. Due to scanty fossil evidence it is unclear which ape or apes contributed to the modern
hominid The Hominidae (), whose members are known as the great apes or hominids (), are a taxonomic family of primates that includes eight extant species in four genera: '' Pongo'' (the Bornean, Sumatran and Tapanuli orangutan); ''Gorilla'' (the east ...
clade, but molecular evidence indicates this ape lived between 18 and 13 million years ago. The first
hominins The Hominini form a taxonomic tribe of the subfamily Homininae ("hominines"). Hominini includes the extant genera ''Homo'' (humans) and '' Pan'' (chimpanzees and bonobos) and in standard usage excludes the genus ''Gorilla'' (gorillas). The t ...
(
bipedal Bipedalism is a form of terrestrial locomotion where an organism moves by means of its two rear limbs or legs. An animal or machine that usually moves in a bipedal manner is known as a biped , meaning 'two feet' (from Latin ''bis'' 'double' ...
apes of the human lineage) appeared in Africa at the very end of the Miocene, including ''
Sahelanthropus ''Sahelanthropus tchadensis'' is an extinct species of the Homininae (African apes) dated to about , during the Miocene epoch. The species, and its genus ''Sahelanthropus'', was announced in 2002, based mainly on a partial cranium, nicknamed '' ...
'', ''
Orrorin ''Orrorin tugenensis'' is a postulated early species of Homininae, estimated at and discovered in 2000. It is not confirmed how ''Orrorin'' is related to modern humans. Its discovery was used to argue against the hypothesis that australopithecin ...
'', and an early form of ''
Ardipithecus ''Ardipithecus'' is a genus of an extinct hominine that lived during the Late Miocene and Early Pliocene epochs in the Afar Depression, Ethiopia. Originally described as one of the earliest ancestors of humans after they diverged from the chimp ...
'' ('' A. kadabba'') The chimpanzee–human divergence is thought to have occurred at this time. The expansion of grasslands in North America also led to an explosive radiation among snakes. Previously, snakes were a minor component of the North American fauna, but during the Miocene, the number of species and their prevalence increased dramatically with the first appearances of
vipers The Viperidae (vipers) are a family of snakes found in most parts of the world, except for Antarctica, Australia, Hawaii, Madagascar, and various other isolated islands. They are venomous and have long (relative to non-vipers), hinged fangs tha ...
and
elapids Elapidae (, commonly known as elapids ; grc, ἔλλοψ ''éllops'' "sea-fish") is a family of snakes characterized by their permanently erect fangs at the front of the mouth. Most elapids are venomous, with the exception of the genus Emydocep ...
in North America and the significant diversification of
Colubridae Colubridae (, commonly known as colubrids , from la, coluber, 'snake') is a family of snakes. With 249 genera, it is the largest snake family. The earliest species of the family date back to the Oligocene epoch. Colubrid snakes are found on ever ...
(including the origin of many modern genera such as ''
Nerodia ''Nerodia'' is a genus of nonvenomous colubrid snakes commonly referred to as water snakes due to their aquatic behavior. The genus includes nine species, all native to North America. Description ''Nerodia'' species vary greatly, but all are ...
'', '' Lampropeltis'', ''
Pituophis ''Pituophis'' is a genus of nonvenomous colubrid snakes, commonly referred to as gopher snakes, pine snakes, and bullsnakes, which are endemic to North America. Geographic range Species and subspecies within the genus ''Pituophis'' are found ...
'' and ''
Pantherophis ''Pantherophis'' is a genus of nonvenomous colubrid snakes endemic to central and eastern regions of North America. It consists of the North American ratsnakes, the foxsnakes, and the cornsnakes. The genus, which contains 10 recognized spec ...
''). In the oceans,
brown algae Brown algae (singular: alga), comprising the class Phaeophyceae, are a large group of multicellular algae, including many seaweeds located in colder waters within the Northern Hemisphere. Brown algae are the major seaweeds of the temperate and po ...
, called
kelp Kelps are large brown algae seaweeds that make up the order Laminariales. There are about 30 different genera. Despite its appearance, kelp is not a plant - it is a heterokont, a completely unrelated group of organisms. Kelp grows in "underwa ...
, proliferated, supporting new species of sea life, including
otter Otters are carnivorous mammals in the subfamily Lutrinae. The 13 extant otter species are all semiaquatic, aquatic, or marine, with diets based on fish and invertebrates. Lutrinae is a branch of the Mustelidae family, which also includes wea ...
s,
fish Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of li ...
and various
invertebrate Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate ...
s.
Cetaceans Cetacea (; , ) is an infraorder of aquatic mammals that includes whales, dolphins, and porpoises. Key characteristics are their fully aquatic lifestyle, streamlined body shape, often large size and exclusively carnivorous diet. They propel them ...
attained their greatest diversity during the Miocene, with over 20 recognized genera of
baleen whale Baleen whales (systematic name Mysticeti), also known as whalebone whales, are a parvorder of carnivorous marine mammals of the infraorder Cetacea (whales, dolphins and porpoises) which use keratinaceous baleen plates (or "whalebone") in their ...
s in comparison to only six living genera. This diversification correlates with emergence of gigantic macro-predators such as megatoothed sharks and raptorial
sperm whale The sperm whale or cachalot (''Physeter macrocephalus'') is the largest of the toothed whales and the largest toothed predator. It is the only living member of the genus ''Physeter'' and one of three extant species in the sperm whale famil ...
s. Prominent examples are '' O. megalodon'' and '' L. melvillei''. Other notable large sharks were '' O. chubutensis'', ''Isurus hastalis'', and ''
Hemipristis serra ''Hemipristis serra'' is an extinct species of weasel shark which existed during the Miocene epoch. It was described by Louis Agassiz Jean Louis Rodolphe Agassiz ( ; ) FRS (For) FRSE (May 28, 1807 – December 14, 1873) was a Swiss-born ...
''. Crocodilians also showed signs of diversification during Miocene. The largest form among them was a gigantic
caiman A caiman (also cayman as a variant spelling) is an alligatorid belonging to the subfamily Caimaninae, one of two primary lineages within the Alligatoridae family, the other being alligators. Caimans inhabit Mexico, Central and South America fro ...
''
Purussaurus ''Purussaurus'' is an extinct genus of giant caiman that lived in South America during the Miocene epoch, from the Friasian to the Huayquerian in the SALMA classification. It is known from skull material found in the Brazilian and Peruvian Amazon ...
'' which inhabited South America. Another gigantic form was a false gharial ''
Rhamphosuchus ''Rhamphosuchus'' ("Beak crocodile") is an extinct genus of gavialid crocodylians. It lived during the Pliocene and its fossils have been found in two regions; the Siwalik Hills of Pakistan and India as well as the Sindh region of Pakistan. Its ...
'', which inhabited modern age
India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area, the List of countries and dependencies by population, second-most populous ...
. A strange form, ''
Mourasuchus ''Mourasuchus'' is an extinct genus of giant, aberrant caiman from the Miocene of South America. Its skull has been described as duck-like, being broad, flat, and very elongate, superficially resembling '' Stomatosuchus'' from the Late Cretaceo ...
'' also thrived alongside ''Purussaurus''. This species developed a specialized filter-feeding mechanism, and it likely preyed upon small fauna despite its gigantic size. The youngest members of
Sebecidae Sebecidae is an extinct family of prehistoric terrestrial sebecosuchian crocodylomorphs. The oldest known member of the group is '' Ogresuchus furatus'' known from the Upper Cretaceous (Maastrichtian) Tremp Formation (Spain). Sebecids were diver ...
, a clade of terrestrial crocodylfomes distantly related to modern crocodilians, are known from the Miocene of South America. The last
Desmostylians The Desmostylia (from Greek δεσμά ''desma'', "bundle", and στῦλος ''stylos'', "pillar") are an extinct order of aquatic mammals that existed from the early Oligocene (Rupelian) to the late Miocene (Tortonian) (). Desmostylians are ...
thrived during this period before becoming the only extinct marine mammal order. The
pinniped Pinnipeds (pronounced ), commonly known as seals, are a widely distributed and diverse clade of carnivorous, fin-footed, semiaquatic, mostly marine mammals. They comprise the extant families Odobenidae (whose only living member is the ...
s, which appeared near the end of the Oligocene, became more aquatic. A prominent genus was ''
Allodesmus ''Allodesmus'' is an extinct genus of pinniped from the middle to late Miocene of California and Japan that belongs to the extinct pinniped family Desmatophocidae. Description and biology ''Allodesmus'' measured about long and weighed . '' ...
''. A ferocious
walrus The walrus (''Odobenus rosmarus'') is a large pinniped, flippered marine mammal with a discontinuous distribution about the North Pole in the Arctic Ocean and subarctic seas of the Northern Hemisphere. The walrus is the only living species in ...
, '' Pelagiarctos'' may have preyed upon other species of pinnipeds including ''Allodesmus''. Furthermore,
South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the sou ...
n waters witnessed the arrival of '' Megapiranha paranensis'', which were considerably larger than modern age
piranha A piranha or piraña (, , or ; or , ) is one of a number of freshwater fish in the family Serrasalmidae, or the subfamily Serrasalminae within the tetra family, Characidae in order Characiformes. These fish inhabit South American rivers, ...
s.
New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island coun ...
's Miocene fossil record is particularly rich. Marine deposits showcase a variety of
cetaceans Cetacea (; , ) is an infraorder of aquatic mammals that includes whales, dolphins, and porpoises. Key characteristics are their fully aquatic lifestyle, streamlined body shape, often large size and exclusively carnivorous diet. They propel them ...
and
penguins Penguins (order Sphenisciformes , family Spheniscidae ) are a group of aquatic flightless birds. They live almost exclusively in the Southern Hemisphere: only one species, the Galápagos penguin, is found north of the Equator. Highly adapt ...
, illustrating the evolution of both groups into modern representatives. The early Miocene
Saint Bathans Fauna The St Bathans fauna is found in the lower Bannockburn Formation of the Manuherikia Group of Central Otago, in the South Island of New Zealand. It comprises a suite of fossilised prehistoric animals from the late Early Miocene (Altonian) period, ...
is the only Cenozoic terrestrial fossil record of the landmass, showcasing a wide variety of not only
bird Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweigh ...
species, including early representatives of clades such as moas, kiwis and
adzebill The adzebills, genus ''Aptornis'', were two closely related bird species, the North Island adzebill, (''Aptornis otidiformis''), and the South Island adzebill, (''Aptornis defossor''), of the extinct family Aptornithidae. The family was endemic ...
s, but also a diverse herpetofauna of sphenodontians,
crocodile Crocodiles (family (biology), family Crocodylidae) or true crocodiles are large semiaquatic reptiles that live throughout the tropics in Africa, Asia, the Americas and Australia. The term crocodile is sometimes used even more loosely to inclu ...
s and
turtle Turtles are an order of reptiles known as Testudines, characterized by a special shell developed mainly from their ribs. Modern turtles are divided into two major groups, the Pleurodira (side necked turtles) and Cryptodira (hidden necked tu ...
as well as a rich terrestrial mammal fauna composed of various species of
bats Bats are mammals of the order Chiroptera.''cheir'', "hand" and πτερόν''pteron'', "wing". With their forelimbs adapted as wings, they are the only mammals capable of true and sustained flight. Bats are more agile in flight than most bi ...
and the enigmatic
Saint Bathans Mammal The Saint Bathans mammal is a currently unnamed extinct primitive mammal from the Early Miocene (Altonian) of New Zealand. A member of the Saint Bathans fauna, it is notable for being a late-surviving "archaic" mammal species, neither a placental ...
.


Oceans

There is evidence from oxygen isotopes at
Deep Sea Drilling Program The Deep Sea Drilling Project (DSDP) was an ocean drilling project operated from 1968 to 1983. The program was a success, as evidenced by the data and publications that have resulted from it. The data are now hosted by Texas A&M University, alth ...
sites that ice began to build up in Antarctica about 36 Ma during the
Eocene The Eocene ( ) Epoch is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene' ...
. Further marked decreases in temperature during the
Middle Miocene The Middle Miocene is a sub-epoch of the Miocene Epoch made up of two stages: the Langhian and Serravallian stages. The Middle Miocene is preceded by the Early Miocene. The sub-epoch lasted from 15.97 ± 0.05 Ma to 11.608 ± 0.005 Ma (million y ...
at 15 Ma probably reflect increased ice growth in Antarctica. It can therefore be assumed that East Antarctica had some glaciers during the early to mid Miocene (23–15 Ma). Oceans cooled partly due to the formation of the
Antarctic Circumpolar Current The Antarctic Circumpolar Current (ACC) is an ocean current that flows clockwise (as seen from the South Pole) from west to east around Antarctica. An alternative name for the ACC is the West Wind Drift. The ACC is the dominant circulation feat ...
, and about 15 million years ago the ice cap in the southern hemisphere started to grow to its present form. The Greenland ice cap developed later, in the
Middle Pliocene Middle or The Middle may refer to: * Centre (geometry), the point equally distant from the outer limits. Places * Middle (sheading), a subdivision of the Isle of Man * Middle Bay (disambiguation) * Middle Brook (disambiguation) * Middle Creek ( ...
time, about 3 million years ago.


Middle Miocene disruption

The "Middle Miocene disruption" refers to a wave of
extinction Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...
s of terrestrial and aquatic life forms that occurred following the Miocene Climatic Optimum (18 to 16 Ma), around 14.8 to 14.5 million years ago, during the
Langhian The Langhian is, in the ICS geologic timescale, an age or stage in the middle Miocene Epoch/Series. It spans the time between 15.97 ± 0.05 Ma and 13.65 ± 0.05 Ma (million years ago) during the Middle Miocene.GeoWhen (2007) The Langhian was a ...
Stage of the mid-Miocene. A major and permanent cooling step occurred between 14.8 and 14.1 Ma, associated with increased production of cold Antarctic deep waters and a major growth of the East Antarctic ice sheet. A Middle Miocene δ18O increase, that is, a relative increase in the heavier isotope of oxygen, has been noted in the Pacific, the Southern Ocean and the South Atlantic.


Impact event

A large
impact event An impact event is a collision between astronomical objects causing measurable effects. Impact events have physical consequences and have been found to regularly occur in planetary systems, though the most frequent involve asteroids, comets or me ...
occurred either during the Miocene (23 Ma – 5.3 Ma) or the Pliocene (5.3 Ma – 2.6 Ma). The event formed the Karakul crater (52 km diameter), in
Tajikistan Tajikistan (, ; tg, Тоҷикистон, Tojikiston; russian: Таджикистан, Tadzhikistan), officially the Republic of Tajikistan ( tg, Ҷумҳурии Тоҷикистон, Jumhurii Tojikiston), is a landlocked country in Centr ...
which is estimated to have an age of less than 23 Ma or less than 5 Ma.


See also

*
Geologic time scale The geologic time scale, or geological time scale, (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the process of relating strata to time) and geochrono ...
*
List of fossil sites This list of fossil sites is a worldwide list of localities known well for the presence of fossils. Some entries in this list are notable for a single, unique find, while others are notable for the large number of fossils found there. Many of t ...
* :Miocene animals


References


Further reading

* Cox, C. Barry & Moore, Peter D. (1993): ''Biogeography. An ecological and evolutionary approach'' (5th ed.). Blackwell Scientific Publications, Cambridge. * Ogg, Jim (2004):
Overview of Global Boundary Stratotype Sections and Points (GSSP's)
. Retrieved 2006-04-30.


External links






Miocene Microfossils: 200+ images of Miocene Foraminifera

Human Timeline (Interactive)
Smithsonian,
National Museum of Natural History The National Museum of Natural History is a natural history museum administered by the Smithsonian Institution, located on the National Mall in Washington, D.C., United States. It has free admission and is open 364 days a year. In 2021, with 7 ...
(August 2016). {{Authority control Geological epochs Neogene geochronology