171 relations: Africa, Alaska, Alkenone, Alps, Ancient Greek, Antarctic Circumpolar Current, Antarctic ice sheet, Antarctica, Archipelago, Arctic, Arctic Ocean, Arecaceae, Asia, Atlantic Ocean, Atmosphere of Earth, Australia, Axial tilt, Azolla, Azolla event, Baltic amber, Baltic Sea, Bartonian, Basilosaurus, Bat, Bibionidae, Bird, Bolca, Bolide, Bouldnor Formation, Carbon, Carbon dioxide, Carbon-12, Carbon-13, Carcharhiniformes, Cenozoic, Charles Lyell, Chesapeake Bay impact crater, Clathrate compound, Coal, Continent, Crocodile, Cupressaceae, Dawn, Deciduous, Decomposition, Denmark, Desert, Drake Passage, Egypt, Elephant, ..., Ellesmere Island, Eocene, Eocene Thermal Maximum 2, Eocene–Oligocene extinction event, Eurasia, Europe, Even-toed ungulate, Evergreen, Extinction event, Fauna, Fish, Flora, Fold (geology), Foraminifera, Forest, Fossil, Fur Formation, Geologic time scale, Geological period, Geology of the Himalaya, Global Boundary Stratotype Section and Point, Global warming potential, Green River Formation, Greenhouse gas, Greenland, Hand, Heat, Himalayas, Hoof, Hydrogen, India, Insular dwarfism, Isle of Wight, Isotope, Isotopes of carbon, Isotopes of oxygen, Lagerstätte, Lake, Laurasia, Leg, List of fossil sites, London Clay, Lutetian, Marsupial, Massignano, Mediterranean Sea, Mesonychid, Mesonyx, Messel pit, Metasequoia glyptostroboides, Methane, Methane clathrate, Mountain formation, Mud, New York City, North America, Northern Europe, Ocean, Ocean gyre, Odd-toed ungulate, Oligocene, Online Etymology Dictionary, Orbital eccentricity, Orogeny, Paleocene, Paleocene–Eocene Thermal Maximum, Paleogene, Paris Basin, Patagonia, Petroleum, Plain, Planet, Plate tectonics, Plecia, Poaceae, Polar stratospheric cloud, Popigai crater, Precession, Predation, Priabonian, Primate, Proboscidea, Proxy (climate), Pythonidae, Rainforest, River, Rock (geology), Rodent, Savanna, Sea ice, Seafloor spreading, Season, Sirenia, Snake, South America, South Asia, Southeast Asia, Southeastern United States, Southern Ocean, Stratum, Subtropics, Supercontinent, Swamp, Temperature, Tethys Ocean, Titanoboa, Tooth, Tropical rainforest, Tundra, Turtle, Umbria, Ungulate, United Arab Emirates, Upwelling, Volcanism, Wadi El Hitan, Water, Weathering, Whale, William Whewell, Ypresian. Expand index (121 more) » « Shrink index
Africa is the world's second largest and second most-populous continent (behind Asia in both categories).
Alaska (Alax̂sxax̂) is a U.S. state located in the northwest extremity of North America.
Alkenones are long-chain unsaturated methyl and ethyl n-ketones produced by a few phytoplankton species of the class Prymnesiophyceae.
The Alps (Alpes; Alpen; Alpi; Alps; Alpe) are the highest and most extensive mountain range system that lies entirely in Europe,The Caucasus Mountains are higher, and the Urals longer, but both lie partly in Asia.
The Ancient Greek language includes the forms of Greek used in ancient Greece and the ancient world from around the 9th century BC to the 6th century AD.
The Antarctic Circumpolar Current (ACC) is an ocean current that flows clockwise from west to east around Antarctica.
The Antarctic ice sheet is one of the two polar ice caps of the Earth.
Antarctica is Earth's southernmost continent.
An archipelago, sometimes called an island group or island chain, is a chain, cluster or collection of islands, or sometimes a sea containing a small number of scattered islands.
The Arctic is a polar region located at the northernmost part of Earth.
The Arctic Ocean is the smallest and shallowest of the world's five major oceans.
The Arecaceae are a botanical family of perennial trees, climbers, shrubs, and acaules commonly known as palm trees (owing to historical usage, the family is alternatively called Palmae).
Asia is Earth's largest and most populous continent, located primarily in the Eastern and Northern Hemispheres.
The Atlantic Ocean is the second largest of the world's oceans with a total area of about.
The atmosphere of Earth is the layer of gases, commonly known as air, that surrounds the planet Earth and is retained by Earth's gravity.
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.
In astronomy, axial tilt, also known as obliquity, is the angle between an object's rotational axis and its orbital axis, or, equivalently, the angle between its equatorial plane and orbital plane.
Azolla (mosquito fern, duckweed fern, fairy moss, water fern) is a genus of seven species of aquatic ferns in the family Salviniaceae.
The Azolla event occurred in the middle Eocene epoch, around, when blooms of the freshwater fern Azolla are thought to have happened in the Arctic Ocean.
The Baltic region is home to the largest known deposit of amber, called Baltic amber or succinite.
The Baltic Sea is a sea of the Atlantic Ocean, enclosed by Scandinavia, Finland, Estonia, Latvia, Lithuania, Russia, Poland, Germany and the North and Central European Plain.
The Bartonian is, in the ICS's geologic time scale, a stage or age in the middle Eocene epoch or series.
Basilosaurus ("king lizard") is a genus of prehistoric cetacean that existed during the Late Eocene, 40 to 35 million years ago (mya).
Bats are mammals of the order Chiroptera; with their forelimbs adapted as wings, they are the only mammals naturally capable of true and sustained flight.
The Bibionidae (March flies and lovebugs) are a family of flies (Diptera).
Birds, also known as Aves, are a group of endothermic vertebrates, characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweight skeleton.
Bolca is a village in the Veneto, on the southern margin of the Italian Alps.
A bolide (French via Latin from the Greek βολίς bolís, "missile") is an extremely bright meteor, especially one that explodes in the atmosphere.
The Bouldnor Formation is a geological formation in the Hampshire Basin of southern England.
Carbon (from carbo "coal") is a chemical element with symbol C and atomic number 6.
Carbon dioxide (chemical formula) is a colorless gas with a density about 60% higher than that of dry air.
Carbon-12 is the more abundant of the two stable isotopes of carbon (Carbon-13 being the other), amounting to 98.93% of the element carbon; its abundance is due to the triple-alpha process by which it is created in stars.
Carbon-13 (13C) is a natural, stable isotope of carbon with a nucleus containing six protons and seven neutrons.
Carcharhiniformes, the ground sharks, with over 270 species, are the largest order of sharks.
The Cenozoic Era meaning "new life", is the current and most recent of the three Phanerozoic geological eras, following the Mesozoic Era and, extending from 66 million years ago to the present day.
Sir Charles Lyell, 1st Baronet, (14 November 1797 – 22 February 1875) was a Scottish geologist who popularised the revolutionary work of James Hutton.
The Chesapeake Bay impact crater was formed by a bolide that impacted the eastern shore of North America about 35.5 ± 0.3 million years ago, in the late Eocene epoch.
A clathrate is a chemical substance consisting of a lattice that traps or contains molecules.
Coal is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers or veins called coal beds or coal seams.
A continent is one of several very large landmasses of the world.
Crocodiles (subfamily Crocodylinae) or true crocodiles are large aquatic reptiles that live throughout the tropics in Africa, Asia, the Americas and Australia.
Cupressaceae is a conifer family, the cypress family, with worldwide distribution.
Dawn, from an Old English verb dagian: "to become day", is the time that marks the beginning of twilight before sunrise.
In the fields of horticulture and botany, the term deciduous (/dɪˈsɪdʒuəs/) means "falling off at maturity" and "tending to fall off", in reference to trees and shrubs that seasonally shed leaves, usually in the autumn; to the shedding of petals, after flowering; and to the shedding of ripe fruit.
Decomposition is the process by which organic substances are broken down into simpler organic matter.
Denmark (Danmark), officially the Kingdom of Denmark,Kongeriget Danmark,.
A desert is a barren area of landscape where little precipitation occurs and consequently living conditions are hostile for plant and animal life.
The Drake Passage or Mar de Hoces—Sea of Hoces—is the body of water between South America's Cape Horn and the South Shetland Islands of Antarctica.
Egypt (مِصر, مَصر, Khēmi), officially the Arab Republic of Egypt, is a transcontinental country spanning the northeast corner of Africa and southwest corner of Asia by a land bridge formed by the Sinai Peninsula.
Elephants are large mammals of the family Elephantidae and the order Proboscidea.
Ellesmere Island (Inuit: Umingmak Nuna, meaning "land of muskoxen"; Île d'Ellesmere) is part of the Qikiqtaaluk Region in the Canadian territory of Nunavut.
The Eocene Epoch, lasting from, is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era.
Eocene Thermal Maximum 2 (ETM-2), also called H-1 or the Elmo (Eocene Layer of Mysterious Origin) event, was a transient period of global warming that occurred approximately 53.7 million years ago (Ma).
The transition between the end of the Eocene and the beginning of the Oligocene is marked by large-scale extinction and floral and faunal turnover (although minor in comparison to the largest mass extinctions).
Eurasia is a combined continental landmass of Europe and Asia.
Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere.
The even-toed ungulates (Artiodactyla) are ungulates (hoofed animals) whose weight is borne equally by the third and fourth toes.
In botany, an evergreen is a plant that has leaves throughout the year, always green.
An extinction event (also known as a mass extinction or biotic crisis) is a widespread and rapid decrease in the biodiversity on Earth.
Fauna is all of the animal life of any particular region or time.
Fish are gill-bearing aquatic craniate animals that lack limbs with digits.
Flora is the plant life occurring in a particular region or time, generally the naturally occurring or indigenous—native plant life.
A geological fold occurs when one or a stack of originally flat and planar surfaces, such as sedimentary strata, are bent or curved as a result of permanent deformation.
Foraminifera (Latin for "hole bearers"; informally called "forams") are members of a phylum or class of amoeboid protists characterized by streaming granular ectoplasm for catching food and other uses; and commonly an external shell (called a "test") of diverse forms and materials.
A forest is a large area dominated by trees.
A fossil (from Classical Latin fossilis; literally, "obtained by digging") is any preserved remains, impression, or trace of any once-living thing from a past geological age.
The Fur Formation is a marine geological formation of Ypresian (Lower Eocene Epoch, c. 56.0-54.5 Ma) age which crops out in the Limfjord region of Denmark from Silstrup via Mors and Fur to Ertebølle, and can be seen in many cliffs and quarries in the area.
The geologic time scale (GTS) is a system of chronological dating that relates geological strata (stratigraphy) to time.
A geological period is one of several subdivisions of geologic time enabling cross-referencing of rocks and geologic events from place to place.
The geology of the Himalaya is a record of the most dramatic and visible creations of modern plate tectonic forces.
A Global Boundary Stratotype Section and Point, abbreviated GSSP, is an internationally agreed upon reference point on a stratigraphic section which defines the lower boundary of a stage on the geologic time scale.
Global warming potential (GWP) is a relative measure of how much heat a greenhouse gas traps in the atmosphere.
The Green River Formation is an Eocene geologic formation that records the sedimentation in a group of intermountain lakes in three basins along the present-day Green River in Colorado, Wyoming, and Utah.
A greenhouse gas is a gas in an atmosphere that absorbs and emits radiant energy within the thermal infrared range.
Greenland (Kalaallit Nunaat,; Grønland) is an autonomous constituent country within the Kingdom of Denmark between the Arctic and Atlantic Oceans, east of the Canadian Arctic Archipelago.
A hand is a prehensile, multi-fingered appendage located at the end of the forearm or forelimb of primates such as humans, chimpanzees, monkeys, and lemurs.
In thermodynamics, heat is energy transferred from one system to another as a result of thermal interactions.
The Himalayas, or Himalaya, form a mountain range in Asia separating the plains of the Indian subcontinent from the Tibetan Plateau.
A hoof, plural hooves or hoofs, is the tip of a toe of an ungulate mammal, strengthened by a thick, horny, keratin covering.
Hydrogen is a chemical element with symbol H and atomic number 1.
India (IAST), also called the Republic of India (IAST), is a country in South Asia.
Insular dwarfism, a form of phyletic dwarfism, is the process and condition of large animals evolving or having a reduced body size when their population's range is limited to a small environment, primarily islands.
The Isle of Wight (also referred to informally as The Island or abbreviated to IOW) is a county and the largest and second-most populous island in England.
Isotopes are variants of a particular chemical element which differ in neutron number.
Carbon (6C) has 15 known isotopes, from 8C to 22C, of which 12C and 13C are stable.
There are three known stable isotopes of oxygen (8O): 16O, 17O, and 18O.
A Lagerstätte (from Lager 'storage, lair' Stätte 'place'; plural Lagerstätten) is a sedimentary deposit that exhibits extraordinary fossils with exceptional preservation—sometimes including preserved soft tissues.
A lake is an area filled with water, localized in a basin, that is surrounded by land, apart from any river or other outlet that serves to feed or drain the lake.
Laurasia was the more northern of two supercontinents (the other being Gondwana) that formed part of the Pangaea supercontinent around (Mya).
A leg is a weight bearing and locomotive anatomical structure, usually having a columnar shape.
This list of fossil sites is a worldwide list of localities known well for the presence of fossils.
The London Clay Formation is a marine geological formation of Ypresian (early Eocene Epoch, c. 56–49 Ma) age which crops out in the southeast of England.
The Lutetian is, in the geologic timescale, a stage or age in the Eocene.
Marsupials are any members of the mammalian infraclass Marsupialia.
Massignano is a comune (municipality) in the Province of Ascoli Piceno in the Italian region Marche, located about southeast of Ancona and about northeast of Ascoli Piceno.
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 Southern Europe and Anatolia, on the south by North Africa and on the east by the Levant.
Mesonychia ("middle claws") is an extinct taxon of small- to large-sized carnivorous ungulates related to the cetartiodactyls.
Mesonyx ("middle claw") is a genus of extinct, superficially wolf-like mesonychid mesonychian mammal: fossils of the various species are found in Early to Late Eocene-age strata in the United States and Early Eocene-aged strata in China, 51.8—51.7 Ma (AEO).
The Messel Pit (Grube Messel) is a disused quarry near the village of Messel, (Landkreis Darmstadt-Dieburg, Hesse) about southeast of Frankfurt am Main, Germany.
Metasequoia glyptostroboides, the dawn redwood, is a fast-growing, endangered deciduous conifer, the sole living species of the genus Metasequoia, one of three species in the subfamily Sequoioideae.
Methane is a chemical compound with the chemical formula (one atom of carbon and four atoms of hydrogen).
Methane clathrate (CH4·5.75H2O) or (4CH4·23H2O), also called methane hydrate, hydromethane, methane ice, fire ice, natural gas hydrate, or gas hydrate, is a solid clathrate compound (more specifically, a clathrate hydrate) in which a large amount of methane is trapped within a crystal structure of water, forming a solid similar to ice.
Mountain formation refers to the geological processes that underlie the formation of mountains.
Mud is a liquid or semi-liquid mixture of water and any combination of different kinds of soil (loam, silt, and clay).
The City of New York, often called New York City (NYC) or simply New York, is the most populous city in the United States.
North America is a continent entirely within the Northern Hemisphere and almost all within the Western Hemisphere; it is also considered by some to be a northern subcontinent of the Americas.
Northern Europe is the general term for the geographical region in Europe that is approximately north of the southern coast of the Baltic Sea.
An ocean (the sea of classical antiquity) is a body of saline water that composes much of a planet's hydrosphere.
In oceanography, a gyre is any large system of circulating ocean currents, particularly those involved with large wind movements.
Members of the order Perissodactyla, also known as odd-toed ungulates, are mammals characterized by an odd number of toes and by hindgut fermentation with somewhat simple stomachs.
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 the exact dates of the start and end of the epoch are slightly uncertain.
The Online Etymology Dictionary is a free online dictionary written and compiled by Douglas Harper that describes the origins of English-language words.
The orbital eccentricity of an astronomical object is a parameter that determines the amount by which its orbit around another body deviates from a perfect circle.
An orogeny is an event that leads to a large structural deformation of the Earth's lithosphere (crust and uppermost mantle) due to the interaction between plate tectonics.
The Paleocene or Palaeocene, the "old recent", is a geological epoch that lasted from about.
The Paleocene–Eocene Thermal Maximum (PETM), alternatively (ETM1), and formerly known as the "Initial Eocene" or "" was a time period with more than 8 °C warmer global average temperature than today.
The Paleogene (also spelled Palaeogene or Palæogene; informally Lower Tertiary or Early Tertiary) is a geologic period and system that spans 43 million years from the end of the Cretaceous Period million years ago (Mya) to the beginning of the Neogene Period Mya.
The Paris Basin is one of the major geological regions of France having developed since the Triassic on a basement formed by the Variscan orogeny.
Patagonia is a sparsely populated region located at the southern end of South America, shared by Argentina and Chile.
Petroleum is a naturally occurring, yellow-to-black liquid found in geological formations beneath the Earth's surface.
In geography, a plain is a flat, sweeping landmass that generally does not change much in elevation.
A planet is an astronomical body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared its neighbouring region of planetesimals.
Plate tectonics (from the Late Latin tectonicus, from the τεκτονικός "pertaining to building") is a scientific theory describing the large-scale motion of seven large plates and the movements of a larger number of smaller plates of the Earth's lithosphere, since tectonic processes began on Earth between 3 and 3.5 billion years ago.
Plecia is a genus of March flies (Bibionidae).
Poaceae or Gramineae is a large and nearly ubiquitous family of monocotyledonous flowering plants known as grasses, commonly referred to collectively as grass.
Polar stratospheric clouds (PSCs), also known as nacreous clouds (from nacre, or mother of pearl, due to its iridescence), are clouds in the winter polar stratosphere at altitudes of.
The Popigai crater (or astrobleme) in Siberia, Russia is tied with the Manicouagan Crater as the fourth largest verified impact crater on Earth.
Precession is a change in the orientation of the rotational axis of a rotating body.
Predation is a biological interaction where a predator (a hunting animal) kills and eats its prey (the organism that is attacked).
The Priabonian is, in the ICS's geologic timescale, the latest age or the upper stage of the Eocene epoch or series.
A primate is a mammal of the order Primates (Latin: "prime, first rank").
The Proboscidea (from the Greek προβοσκίς and the Latin proboscis) are a taxonomic order of afrotherian mammals containing one living family, Elephantidae, and several extinct families.
In the study of past climates ("paleoclimatology"), climate proxies are preserved physical characteristics of the past that stand in for direct meteorological measurements and enable scientists to reconstruct the climatic conditions over a longer fraction of the Earth's history.
The Pythonidae, commonly known simply as pythons, from the Greek word python (πυθων), are a family of nonvenomous snakes found in Africa, Asia, and Australia.
Rainforests are forests characterized by high rainfall, with annual rainfall in the case of tropical rainforests between, and definitions varying by region for temperate rainforests.
A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake or another river.
Rock or stone is a natural substance, a solid aggregate of one or more minerals or mineraloids.
Rodents (from Latin rodere, "to gnaw") are mammals of the order Rodentia, which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws.
A savanna or savannah is a mixed woodland grassland ecosystem characterised by the trees being sufficiently widely spaced so that the canopy does not close.
Sea ice arises as seawater freezes.
Seafloor spreading is a process that occurs at mid-ocean ridges, where new oceanic crust is formed through volcanic activity and then gradually moves away from the ridge.
A season is a division of the year marked by changes in weather, ecology, and amount of daylight.
The Sirenia, commonly referred to as sea cows or sirenians, are an order of fully aquatic, herbivorous mammals that inhabit swamps, rivers, estuaries, marine wetlands, and coastal marine waters.
Snakes are elongated, legless, carnivorous reptiles of the suborder Serpentes.
South America is a continent in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere.
South Asia or Southern Asia (also known as the Indian subcontinent) is a term used to represent the southern region of the Asian continent, which comprises the sub-Himalayan SAARC countries and, for some authorities, adjoining countries to the west and east.
Southeast Asia or Southeastern Asia is a subregion of Asia, consisting of the countries that are geographically south of China, east of India, west of New Guinea and north of Australia.
The Southeastern United States (Sureste de Estados Unidos, Sud-Est des États-Unis) is the eastern portion of the Southern United States, and the southern portion of the Eastern United States.
The Southern Ocean, also known as the Antarctic Ocean or the Austral Ocean, comprises the southernmost waters of the World Ocean, generally taken to be south of 60° S latitude and encircling Antarctica.
In geology and related fields, a stratum (plural: strata) is a layer of sedimentary rock or soil, or igneous rock that were formed at the Earth's surface, with internally consistent characteristics that distinguish it from other layers.
The subtropics are geographic and climate zones located roughly between the tropics at latitude 23.5° (the Tropic of Cancer and Tropic of Capricorn) and temperate zones (normally referring to latitudes 35–66.5°) north and south of the Equator.
In geology, a supercontinent is the assembly of most or all of Earth's continental blocks or cratons to form a single large landmass.
A swamp is a wetland that is forested.
Temperature is a physical quantity expressing hot and cold.
The Tethys Ocean (Ancient Greek: Τηθύς), Tethys Sea or Neotethys was an ocean during much of the Mesozoic Era located between the ancient continents of Gondwana and Laurasia, before the opening of the Indian and Atlantic oceans during the Cretaceous Period.
Titanoboa, is an extinct genus of snakes that is known to have lived in present-day La Guajira in northeastern Colombia.
A tooth (plural teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food.
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 equatorial evergreen rainforest.
In physical geography, tundra is a type of biome where the tree growth is hindered by low temperatures and short growing seasons.
Turtles are diapsids of the order Testudines (or Chelonii) characterized by a special bony or cartilaginous shell developed from their ribs and acting as a shield.
Umbria is a region of central Italy.
Ungulates (pronounced) are any members of a diverse group of primarily large mammals that includes odd-toed ungulates such as horses and rhinoceroses, and even-toed ungulates such as cattle, pigs, giraffes, camels, deer, and hippopotami.
The United Arab Emirates (UAE; دولة الإمارات العربية المتحدة), sometimes simply called the Emirates (الإمارات), is a federal absolute monarchy sovereign state in Western Asia at the southeast end of the Arabian Peninsula on the Persian Gulf, bordering Oman to the east and Saudi Arabia to the south, as well as sharing maritime borders with Qatar to the west and Iran to the north.
Upwelling is an oceanographic phenomenon that involves wind-driven motion of dense, cooler, and usually nutrient-rich water towards the ocean surface, replacing the warmer, usually nutrient-depleted surface water.
Volcanism is the phenomenon of eruption of molten rock (magma) onto the surface of the Earth or a solid-surface planet or moon, where lava, pyroclastics and volcanic gases erupt through a break in the surface called a vent.
Wadi Al-Hitan, (وادي الحيتان, "Whale Valley") is a paleontological site in the Faiyum Governorate of Egypt, some 150 km southwest of Cairo.
Water is a transparent, tasteless, odorless, and nearly colorless chemical substance that is the main constituent of Earth's streams, lakes, and oceans, and the fluids of most living organisms.
Weathering is the breaking down of rocks, soil, and minerals as well as wood and artificial materials through contact with the Earth's atmosphere, water, and biological organisms.
Whales are a widely distributed and diverse group of fully aquatic placental marine mammals.
William Whewell (24 May 1794 – 6 March 1866) was an English polymath, scientist, Anglican priest, philosopher, theologian, and historian of science.
In the geologic timescale the Ypresian is the oldest age or lowest stratigraphic stage of the Eocene.