The Eocene ( [See:
]
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Letter from William Whewell to Charles Lyell dated 31 January 1831 in:
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From p. 55: "The period next antecedent we shall call Eocene, from ήως, aurora, and χαινος, recens, because the extremely small proportion of living species contained in these strata, indicates what may be considered the first commencement, or dawn, of the existing state of the animate creation."
The Eocene spans the time from the end of the Paleocene Epoch to the beginning of the Oligocene Epoch. The start of the Eocene is marked by a brief period in which the concentration of the carbon isotope 13C in the atmosphere was exceptionally low in comparison with the more common isotope 12C. The average temperature of Earth at the beginning of the Eocene was about 27 degrees Celsius.[The extinction of the Hantkeninidae, a planktonic family of foraminifera became generally accepted as marking the Eocene-Oligocene boundary; in 1998 Massignano in Umbria, central Italy, was designated the Global Boundary Stratotype Section and Point (GSSP).] though their exact dates are slightly uncertain.
Etymology
The term "Eocene" is derived from
Ancient Greek Ἠώς (
Ēṓs) meaning "Dawn", and καινός
kainos meaning "new" or "recent", as the epoch saw the dawn of recent, or modern, life.
Scottish geologist Charles Lyell (ignoring the Quaternary) divided the Tertiary Epoch into the Eocene, Miocene, Pliocene, and New Pliocene (Holocene) Periods in 1833.
Geology
Boundaries
The Eocene is a dynamic epoch that represents global climatic transitions between two climatic extremes, transitioning from the hot house to the cold house. The beginning of the Eocene is marked by the Paleocene–Eocene Thermal Maximum, a short period of intense warming and ocean acidification brought about by the release of carbon en masse into the atmosphere and ocean systems,
[ which led to a mass extinction of 30–50% of benthic foraminifera (single-celled species which are used as of the health of a marine ecosystem)—one of the largest in the Cenozoic.]
The middle Eocene was characterized by the shift towards a cooler climate at the end of the Early Eocene Climatic Optimum, around 47.8 Ma, which was briefly interrupted by another warming event, the Middle Eocene Climatic Optimum.
The end of the Eocene was also marked by the Eocene–Oligocene extinction event, also known as the Grande Coupure.
Stratigraphy
The Eocene is conventionally divided into early (56–47.8 Ma), middle (47.8–38 Ma), and late (38–33.9 Ma) subdivisions.
The Western North American floras of the Eocene were divided into four floral "stages" by Jack Wolfe (1968) based on work with the Puget Group fossils of King County, Washington. The four stages, Franklinian, Fultonian, Ravenian, and Kummerian covered the Early Eocene through early Oligocene, and three of the four were given informal early/late substages. Wolfe tentatively deemed the Franklinian as Early Eocene, the Fultonian as Middle Eocene, the Ravenian as Late, and the Kummerian as Early Oligocene.
Palaeogeography and tectonics
During the Eocene, the continued to plate tectonics toward their present positions. At the beginning of the period, Australia and Antarctica remained connected, and warm equatorial currents may have mixed with colder Antarctic waters, distributing the heat around the planet and keeping global temperatures high. When Australia split from the southern continent around 45 Ma, the warm equatorial currents were routed away from Antarctica. An isolated cold water channel developed between the two continents.
The northern supercontinent of Laurasia began to fragment, as Europe, Greenland and North America drifted apart.
In western North America, the Laramide Orogeny came to an end in the Eocene, and compression was replaced with crustal extension that ultimately gave rise to the Basin and Range Province.
At about 35 Ma, an asteroid impact on the eastern coast of North America formed the Chesapeake Bay impact crater.
The Tethys Sea finally closed with the collision of Africa and Eurasia,
Eurasia was separated in three different landmasses 50 Ma; Western Europe, Balkanatolia and Asia. About 40 Ma, Balkanatolia and Asia were connected, while Europe was connected 34 Ma.
Indian Plate collided with Asia, folding to initiate formation of the .
Climate
The Eocene Epoch contained a wide variety of climate conditions that includes the warmest climate in the
Cenozoic Era, and arguably the warmest time interval since the Permian-Triassic mass extinction and Early Triassic, and ends in an icehouse climate.
The evolution of the Eocene climate began with warming after the end of the Paleocene–Eocene Thermal Maximum (PETM) at 56 Ma to a maximum during the Eocene Optimum at around 49 Ma. During this period of time, little to no ice was present on Earth with a smaller difference in temperature from the equator to the poles.
Because of this the maximum sea level was 150 meters higher than current levels.
Following the maximum was a descent into an icehouse climate from the Eocene Optimum to the Eocene–Oligocene transition at 34 Ma. During this decrease, ice began to reappear at the poles, and the Eocene–Oligocene transition is the period of time when the Antarctic ice sheet began to rapidly expand.
Early Eocene
Greenhouse gases, in particular
carbon dioxide and
methane, played a significant role during the Eocene in controlling the surface temperature. The end of the PETM was met with very large sequestration of carbon dioxide into the forms of methane clathrate,
coal, and
crude oil at the bottom of the
Arctic Ocean, that reduced the atmospheric carbon dioxide.
[ This event was similar in magnitude to the massive release of greenhouse gasses at the beginning of the PETM, and it is hypothesized that the sequestration was mainly due to organic carbon burial and weathering of silicates. For the early Eocene there is much discussion on how much carbon dioxide was in the atmosphere. This is due to numerous proxies representing different atmospheric carbon dioxide content. For example, diverse geochemical and paleontological proxies indicate that at the maximum of global warmth the atmospheric carbon dioxide values were at 700–900 ppm,][ while model simulations suggest a concentration of 1,680 ppm fits best with deep sea, sea surface, and near-surface air temperatures of the time.][ This large influx of carbon dioxide could be attributed to volcanic out-gassing due to North Atlantic rifting or oxidation of methane stored in large reservoirs deposited from the PETM event in the sea floor or wetland environments.][ For contrast, today the carbon dioxide levels are at 400 ppm or 0.04%.
]
During the early Eocene, methane was another greenhouse gas that had a drastic effect on the climate. Methane has 30 times more of a warming effect than carbon dioxide on a 100-year scale (i.e., methane has a global warming potential of 29.8±11).[ The atmospheric methane concentration today is 0.000179% or 1.79 ppmv. As a result of the warmer climate and the sea level rise associated with the early Eocene, more wetlands, more forests, and more coal deposits would have been available for methane release. If we compare the early Eocene production of methane to current levels of atmospheric methane, the early Eocene would have produced triple the amount of methane. The warm temperatures during the early Eocene could have increased methane production rates, and methane that is released into the atmosphere would in turn warm the troposphere, cool the stratosphere, and produce water vapor and carbon dioxide through oxidation. Biogenic production of methane produces carbon dioxide and water vapor along with the methane, as well as yielding infrared radiation. The breakdown of methane in an atmosphere containing oxygen produces carbon monoxide, water vapor and infrared radiation. The carbon monoxide is not stable, so it eventually becomes carbon dioxide and in doing so releases yet more infrared radiation. Water vapor traps more infrared than does carbon dioxide. At about the beginning of the Eocene Epoch (55.8–33.9 Ma) the amount of oxygen in the Earth's atmosphere more or less doubled.]
During the warming in the early Eocene between 55 and 52 Ma, there were a series of short-term changes of carbon isotope composition in the ocean.
Equable climate problem
One of the unique features of the Eocene's climate as mentioned before was the equable and homogeneous climate that existed in the early parts of the Eocene. A multitude of proxies support the presence of a warmer equable climate being present during this period of time. A few of these proxies include the presence of fossils native to warm climates, such as , located in the higher latitudes,[ the presence in the high latitudes of frost-intolerant flora such as palm trees which cannot survive during sustained freezes,][ and fossils of snakes found in the tropics that would require much higher average temperatures to sustain them.][ TEX86 BAYSPAR measurements indicate extremely high sea surface temperatures of to at low latitudes,][ With these bottom water temperatures, temperatures in areas where deep water forms near the poles are unable to be much cooler than the bottom water temperatures.
]
An issue arises, however, when trying to model the Eocene and reproduce the results that are found with the proxy data.[ Using all different ranges of greenhouse gasses that occurred during the early Eocene, models were unable to produce the warming that was found at the poles and the reduced seasonality that occurs with winters at the poles being substantially warmer. The models, while accurately predicting the tropics, tend to produce significantly cooler temperatures of up to colder than the actual determined temperature at the poles.][ This error has been classified as the "equable climate problem". To solve this problem, the solution would involve finding a process to warm the poles without warming the tropics. Some hypotheses and tests which attempt to find the process are listed below.
]
Large lakes
Due to the nature of water as opposed to land, less temperature variability would be present if a large body of water is also present. In an attempt to try to mitigate the cooling polar temperatures, large lakes were proposed to mitigate seasonal climate changes.[ To replicate this case, a lake was inserted into North America and a climate model was run using varying carbon dioxide levels. The model runs concluded that while the lake did reduce the seasonality of the region greater than just an increase in carbon dioxide, the addition of a large lake was unable to reduce the seasonality to the levels shown by the floral and faunal data.
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Ocean heat transport
The transport of heat from the tropics to the poles, much like how ocean heat transport functions in modern times, was considered a possibility for the increased temperature and reduced seasonality for the poles.[ With the increased sea surface temperatures and the increased temperature of the deep ocean water during the early Eocene, one common hypothesis was that due to these increases there would be a greater transport of heat from the tropics to the poles. Simulating these differences, the models produced lower heat transport due to the lower temperature gradients and were unsuccessful in producing an equable climate from only ocean heat transport.
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Orbital parameters
While typically seen as a control on ice growth and seasonality, the orbital parameters were theorized as a possible control on continental temperatures and seasonality. Simulating the Eocene by using an ice free planet, eccentricity, obliquity, and precession were modified in different model runs to determine all the possible different scenarios that could occur and their effects on temperature. One particular case led to warmer winters and cooler summer by up to 30% in the North American continent, and it reduced the seasonal variation of temperature by up to 75%. While orbital parameters did not produce the warming at the poles, the parameters did show a great effect on seasonality and needed to be considered.[
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Polar stratospheric clouds
Another method considered for producing the warm polar temperatures were polar stratospheric clouds.[ Polar stratospheric clouds are clouds that occur in the lower stratosphere at very low temperatures. Polar stratospheric clouds have a great impact on radiative forcing. Due to their minimal albedo properties and their optical thickness, polar stratospheric clouds act similar to a greenhouse gas and trap outgoing longwave radiation. Different types of polar stratospheric clouds occur in the atmosphere: polar stratospheric clouds that are created due to interactions with nitric or sulfuric acid and water (Type I) or polar stratospheric clouds that are created with only water ice (Type II).
]
Methane is an important factor in the creation of the primary Type II polar stratospheric clouds that were created in the early Eocene.[ Since water vapor is the only supporting substance used in Type II polar stratospheric clouds, the presence of water vapor in the lower stratosphere is necessary where in most situations the presence of water vapor in the lower stratosphere is rare. When methane is oxidized, a significant amount of water vapor is released. Another requirement for polar stratospheric clouds is cold temperatures to ensure condensation and cloud production. Polar stratospheric cloud production, since it requires the cold temperatures, is usually limited to nighttime and winter conditions. With this combination of wetter and colder conditions in the lower stratosphere, polar stratospheric clouds could have formed over wide areas in Polar Regions.
]
To test the polar stratospheric clouds effects on the Eocene climate, models were run comparing the effects of polar stratospheric clouds at the poles to an increase in atmospheric carbon dioxide.[ The polar stratospheric clouds had a warming effect on the poles, increasing temperatures by up to 20 °C in the winter months. A multitude of feedbacks also occurred in the models due to the polar stratospheric clouds' presence. Any ice growth was slowed immensely and would lead to any present ice melting. Only the poles were affected with the change in temperature and the tropics were unaffected, which with an increase in atmospheric carbon dioxide would also cause the tropics to increase in temperature. Due to the warming of the troposphere from the increased greenhouse effect of the polar stratospheric clouds, the stratosphere would cool and would potentially increase the amount of polar stratospheric clouds.
]
While the polar stratospheric clouds could explain the reduction of the equator to pole temperature gradient and the increased temperatures at the poles during the early Eocene, there are a few drawbacks to maintaining polar stratospheric clouds for an extended period of time. Separate model runs were used to determine the sustainability of the polar stratospheric clouds.[ It was determined that in order to maintain the lower stratospheric water vapor, methane would need to be continually released and sustained. In addition, the amounts of ice and condensation nuclei would need to be high in order for the polar stratospheric cloud to sustain itself and eventually expand.
]
Middle Eocene
The Eocene is not only known for containing the warmest period during the Cenozoic; it also marked the decline into an icehouse climate and the rapid expansion of the Antarctic ice sheet. The transition from a warming climate into a cooling climate began at around 49 Ma. Isotopes of carbon and oxygen indicate a shift to a global cooling climate.[ The cause of the cooling has been attributed to a significant decrease of >2,000 ppm in atmospheric carbon dioxide concentrations.][ One proposed cause of the reduction in carbon dioxide during the warming to cooling transition was the azolla event. With the equable climate during the early Eocene, warm temperatures in the arctic allowed for the growth of azolla, which is a floating aquatic fern, on the Arctic Ocean. The significantly high amounts of carbon dioxide also acted to facilitate azolla blooms across the Arctic Ocean. Compared to current carbon dioxide levels, these azolla grew rapidly in the enhanced carbon dioxide levels found in the early Eocene.][ The isolation of the Arctic Ocean, evidenced by euxinia that occurred at this time,][ The azolla event could have led to a draw down of atmospheric carbon dioxide of up to 470 ppm. Assuming the carbon dioxide concentrations were at 900 ppmv prior to the Azolla Event they would have dropped to 430 ppmv, or 30 ppmv more than they are today, after the Azolla Event.][ This cooling trend at the end of the EECO has also been proposed to have been caused by increased siliceous plankton productivity and marine carbon burial, which also helped draw carbon dioxide out of the atmosphere.][ Cooling after this event, part of a trend known as the Middle-Late Eocene Cooling (MLEC),][ Many regions of the world became more arid and cold over the course of the stage, such as the Fushun Basin.][ In East Asia, lake level changes were in sync with global sea level changes over the course of the MLEC.]
Global cooling continued until there was a major reversal from cooling to warming in the Bartonian. This warming event, signifying a sudden and temporary reversal of the cooling conditions, is known as the Middle Eocene Climatic Optimum (MECO).[ A similar shift in carbon isotopes is known from the Northern Hemisphere in the Scaglia Limestones of Italy.][ A sharp increase in atmospheric carbon dioxide was observed with a maximum of 4,000 ppm: the highest amount of atmospheric carbon dioxide detected during the Eocene.][ Other studies suggest a more modest rise in carbon dioxide levels.][ Recent studies have mentioned, however, that the removal of the ocean between Asia and India could have released significant amounts of carbon dioxide.][ Another hypothesis still implicates a diminished negative feedback of silicate weathering as a result of continental rocks having become less weatherable during the warm Early and Middle Eocene, allowing volcanically released carbon dioxide to persist in the atmosphere for longer.][
]
Late Eocene
At the end of the MECO, the MLEC resumed.[ Cooling and the carbon dioxide drawdown continued through the late Eocene and into the Eocene–Oligocene transition around 34 Ma.][ The end of the Eocene and beginning of the Oligocene is marked with the massive expansion of area of the Antarctic ice sheet that was a major step into the icehouse climate.][ Multiple proxies, such as oxygen isotopes and , indicate that at the Eocene–Oligocene transition, the atmospheric carbon dioxide concentration had decreased to around 750–800 ppm, approximately twice that of present levels.][ Along with the decrease of atmospheric carbon dioxide reducing the global temperature, orbital factors in ice creation can be seen with 100,000-year and 400,000-year fluctuations in benthic oxygen isotope records.][ Another major contribution to the expansion of the ice sheet was the creation of the Antarctic Circumpolar Current.][ The creation of the Antarctic circumpolar current would isolate the cold water around the Antarctic, which would reduce heat transport to the Antarctic][ along with creating that result in the upwelling of colder bottom waters.][ The issue with this hypothesis of the consideration of this being a factor for the Eocene-Oligocene transition is the timing of the creation of the circulation is uncertain.][ For Drake Passage, sediments indicate the opening occurred ~41 Ma while tectonics indicate that this occurred ~32 Ma. Solar activity did not change significantly during the greenhouse-icehouse transition across the Eocene-Oligocene boundary.]
Flora
During the early-middle Eocene, forests covered most of the Earth including the poles. Tropical forests extended across much of modern Africa, South America, Central America, India, South-east Asia and China. Paratropical forests grew over North America, Europe and Russia, with broad-leafed evergreen and broad-leafed deciduous forests at higher latitudes.
Polar forests were quite extensive. and even preserved remains of trees such as Cupressaceae and Metasequoia from the Eocene have been found on Ellesmere Island in the Arctic. Even at that time, Ellesmere Island was only a few degrees in latitude further south than it is today. Fossils of subtropical and even tropical trees and plants from the Eocene also have been found in Greenland and Alaska. Tropical rainforests grew as far north as northern North America and Europe.
were growing as far north as Alaska and northern Europe during the early Eocene, although they became less abundant as the climate cooled.
The earliest definitive Eucalyptus fossils were dated from 51.9 Ma, and were found in the Laguna del Hunco deposit in Chubut province in Argentina.
Cooling began mid-period, and by the end of the Eocene continental interiors had begun to dry, with forests thinning considerably in some areas. The newly evolved grasses began to expand during the climatic cooling and drying following the extreme warmth of the EECO, with subhumid Savanna being known from South America since the Middle Eocene.
The cooling also brought changes. Deciduous trees, better able to cope with large temperature changes, began to overtake evergreen tropical species. By the end of the period, deciduous forests covered large parts of the northern continents, including North America, Eurasia and the Arctic, and rainforests held on only in equatorial South America, Africa, India and Australia.
Antarctica began the Eocene fringed with a warm temperate to sub-tropical rainforest. Pollen found in Prydz Bay from the Eocene suggest taiga forest existed there.
File:Nuphar carlquistii seeds 01b.jpg| Nuphar seeds, Nymphaeaceae, Ypresian
File:Iodes sp. seed, Icacinaceae, London Clay pyrite fossil, by Omar Hoftun.png| Iodes tree seed, Icacinaceae, London Clay
File:Mastixia sp. seed, Nyssaceae, London Clay pyrite fossil, by Omar Hoftun.jpg| Mastixia tree seed, Nyssaceae, London Clay
File:Ocotea sp. fruit, Lauraceae, London Clay pyrite fossil, by Omar Hoftun.png| Ocotea tree seed, Lauraceae, London clay
File:Macginitiea wyomingensis Houston Museum of Natural Science - DSC01946.jpg| Macginitiea leaf, Platanaceae, Clarno Formation, Oregon
File:Eocene fossil flower, Clare Family Florissant Fossil Quarry, Florissant, Colorado, USA - 20100807.jpg|Flower, Florissant Formation, Colorado
Fauna
During the Eocene, plants and marine faunas became quite modern. Many modern bird orders first appeared in the Eocene. The Eocene oceans were warm and teeming with fish and other sea life.
Vertebrates
Mammals
The oldest known of most of the modern mammal orders appear within a Uintan. At the beginning of the Eocene, several new mammal groups arrived in North America. These modern mammals, like , perissodactyls, and , had features like long, thin , feet, and capable of grasping, as well as differentiated teeth adapted for chewing. Insular dwarfism forms reigned. All the members of the new mammal orders were small, under 10 kg; based on comparisons of tooth size, Eocene mammals were only 60% of the size of the primitive Palaeocene mammals that preceded them. They were also smaller than the mammals that followed them. It is assumed that the hot Eocene temperatures favored smaller animals that were better able to manage the heat.[Abigail R. D’Ambrosia et al. (2017) Repetitive mammalian dwarfing during ancient greenhouse warming events.Sci. Adv.3,e1601430.DOI:10.1126/sciadv.1601430][Katherina B. Searing et al
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Rodents were widespread. East Asian rodent faunas declined in diversity when they shifted from ctenodactyloid-dominant to cricetid–dipodid-dominant after the MECO.
Both groups of modern (hoofed animals) became prevalent because of a major radiation between Europe and North America, along with carnivorous ungulates like Mesonyx. Early forms of many other modern mammalian orders appeared, including (most notably the Eohippus), , Proboscidea (elephants), primates, and . Older primitive forms of mammals declined in variety and importance. Important Eocene land fauna fossil remains have been found in western North America, Europe, Patagonia, Egypt, and southeast Asia. Marine fauna are best known from South Asia and the southeast United States.
After the Paleocene–Eocene Thermal Maximum, members of the Equoidea arose in North America and Europe, giving rise to some of the earliest such as Sifrhippus and basal European equoids such as the palaeothere Hyracotherium.
Established large-sized mammals of the Eocene include the Uintatherium, Arsinoitherium, and brontotheres, in which the former two, unlike the latter, did not belong to ungulates but groups that became extinct shortly after their establishments.
Large terrestrial mammalian predators had already existed since the Paleocene, but new forms now arose like Hyaenodon and Daphoenus (the earliest lineage of a once-successful predatory family known as bear dogs). Entelodonts meanwhile established themselves as some of the largest omnivores. The first nimravids, including Dinictis, established themselves as amongst the first feliforms to appear. Their groups became highly successful and continued to live past the Eocene.
Basilosaurus is a well-known Eocene whale, but whales as a group had become very diverse during the Eocene, which is when the major transitions from being terrestrial to fully aquatic in occurred. The first were evolving at this time, and would eventually evolve into the extant and .
File:Dinoceras mirabile Marsh MNHN.jpg|Cast of skull of Uintatherium anceps, a dinoceratan
File:Andrewsarchus09DB.jpg|Reconstruction of Andrewsarchus, an artiodactyl
File:Basilosaurus isis fossil, Nantes History Museum 03.jpg| Basilosaurus, a whale
File:Pakicetus Canada.jpg| Pakicetus, an amphibious cetacean
File:Moeritherium lyonsi (fossil mammal) (Eocene) (32167459460).jpg| Moeritherium, a basal proboscidean
File:Brontotherium skull IMG 4441.jpg| Megacerops, a brontotheriid
File:Hyracodon nebraskensis.jpg| Hyracodon, a perissodactyl
File:Leptictidium auderiense skeleton.JPG| Leptictidium, a small mammal, likely bipedal
File:Peratherium skull.jpg| Peratherium, a herpetotheriid
File:Hesperocyon skull Smithsonian.jpg| Hesperocyon, a canid
Birds
Eocene birds include some enigmatic groups with resemblances to modern forms, some of which continued from the Paleocene. Bird taxa of the Eocene include carnivorous , such as Messelasturidae, Halcyornithidae, large flightless forms such as Gastornis and Eleutherornis,
Many Eocene birds in Central Europe evolved tuberculate vertebrae as an adaptation against predation, with flightless birds facing low predation pressure during this time as a result.
File:Primobucco mcgrewi USNM PAL 336284 img1.jpg| Primobucco, an early relative of the Coraciidae
File:Pseudocrypturus Smithsonian fossil.jpg| Pseudocrypturus, Early Eocene, Wyoming
File:Diatrymaskeleton.JPG| Gastornis, a flightless bird
Fishes
Fishes, both Chondrichthyes such as sharks and rays, and Osteichthyes (bony fishes), are abundant in the London Clay.
File:Carcharocles sokolowi teeth.png|Teeth of Otodus sokolovi, an otodontid shark
File:Xiphodolamia.jpg|Teeth of Xiphodolamia. a mackerel shark, London Clay
File:Heliobatis radians with two Knightia eocaena (3bce1f6e-f693-43d1-aa0f-67ba7fc50895).tif| Heliobatis and Knightia
File:FOS655.jpg|Eel, cf. Echelus branchialis, collected by Louis Agassiz
File:FOS794.jpg|Vertebrae of a Lamniformes shark, London Clay, Isle of Sheppey
Reptiles
Reptile fossils from this time, such as fossils of pythons and , are abundant.
File:Turtle with crocodile bite marks, Eocene, Green River Formation, Kemmerer, Lincoln County, Wyoming, USA - Houston Museum of Natural Science - DSC02006.JPG| Hummelichelys with crocodile bite marks
File:Borealosuchus wilsoni (15529256785).jpg| Borealosuchus, a crocodyliform
Molluscs
File:Cerithium giganteum, snails, Middle Eocene, Verona, Italy - Houston Museum of Natural Science - DSC01968.jpg| Cerithium shells
Arthropods
Several rich fossil insect faunas are known from the Eocene, notably the Baltic amber found mainly along the south coast of the Baltic Sea,
File:Harpactocarinus punctulatus, crab, Eocene, Rialo Formation, Monte Baldo Quarry, Verona, Italy - Houston Museum of Natural Science - DSC01954.JPG| Harpactocarcinus, a crab
File:Palaeoncoderes eocenicus L. PITON et N. THEOBALD 1937 Holotype.jpg| Palaeoncoderes, a beetle
Other phyla
File:Echinolampas ovalis M Eocene Civrac-en-Médoc France.JPG| Echinolampas, a sea urchin
Microbes
Calcareous nannoplankton were a prominent feature of Eocene marine ecosystems.
See also
Notes
Further reading
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Ogg, Jim; June, 2004, Overview of Global Boundary Stratotype Sections and Points (GSSP's) Global Stratotype Sections and Points Accessed April 30, 2006.
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Stanley, Steven M. Earth System History. New York: W.H. Freeman and Company, 1999.
External links
