Cenozoic era epochs

Cenozoic era. In geologic time, the Cenozoic Era, the third era in the Phanerozoic Eon, follows the Mesozoic Era and spans the time between roughly 65 million years ago (mya) and present day. On the geologic time scale, Earth is currently in the Cenozoic Era of the Phanerozoic Eon. The Cenozoic Era contains two geologic time …

Cenozoic era epochs. The Paleocene Epoch/Series is the first of the Cenozoic Era/Erathem. It is the first of five epochs in the Tertiary Period and the first of three in the Paleogene, which is treated either as a period in its own right or as a subdivision of the Tertiary. The Paleocene succeeds the Cretaceous Period/System and precedes the Eocene Epoch.

Which era is divided into periods and epochs? Cenozoic Era The two periods of the Cenozoic Era are the Tertiary and Quaternary. A period is divided into an even smaller unit called an epoch. What is the oldest epoch in the Cenozoic era? Paleogene Period , also spelled Palaeogene Period , oldest of the three stratigraphic …

The Cenozoic Era was initially referred to as the third and fourth periods. These two periods are still called the Tertiary and Quaternary. The Quaternary period is composed of our present epoch (the Holocene) and the Pleistocene. The Tertiary is divided into five epochs – Pliocene, Miocene, Oligocene, Eocene and Paleocene.Oct 30, 2012 · Salix sp. leaf. Liquidambar sp. seed pod. The Paleogene Period* is the first of three periods comprising the Cenozoic Era. The Cenozoic, sometimes known as the "Age of Mammals", as the Mesozoic was the "Age of Reptiles", is known by its Epochs. The Paleogene is composed of the first three of these Epochs, (Paleocene, Eocene, and Oligocene Epochs). 1 de mai. de 2006 ... The Pleistocene epoch is marked by five or more major ice ages, the last of which ended at about 11,000 years ago. At this time, somewhere ...Sep 29, 2023 · Tertiary Period, former official interval of geologic time lasting from approximately 66 million to 2.6 million years ago. It is the traditional name for the first of two periods in the Cenozoic Era (66 million years ago to the present); the second is the Quaternary Period (2.6 million years ago to the present). During the Cenozoic Era, the Paleogene Period is broken up into the Paleocene, Eocene, and Oligocene Epochs. The Neogene Period is broken up into the Miocene and Pliocene Epochs. Each one of these earlier Epochs is marked by important evolutionary and geologic changes that define these bands of time.

The Cenozoic is divided into three periods: the Paleogene, Neogene, and Quaternary; and seven epochs: the Paleocene, Eocene, Oligocene, Miocene, Pliocene, ...The Cenozoic Era is generally divided into three periods; each is further divided into several epochs. The Paleogene Period (66 million to 23 million years ago) is divided into the Paleocene, Eocene, and Oligocene epochs. The Neogene Period (23 million to 2.6 million years ago) contains the Miocene and Pliocene epochs. The succeeding eon is the Phanerozoic, divided into three eras: the Palaeozoic, an era of arthropods, fishes, and the first life on land; the Mesozoic, which spanned the rise, reign, and climactic extinction of the non-avian dinosaurs; and the Cenozoic, which saw the rise of mammals. Recognizable humans emerged at most 2 million years ago, a ...The Giant Mammals of the Eocene, Oligocene, and Miocene Epochs. The Eocene epoch, from 56 to 34 million years ago, witnessed the first plus-sized herbivorous mammals. The success of Coryphodon, a half-ton plant-eater with a tiny, dinosaur-sized brain, can be inferred by its wide distribution across early Eocene North America and …and Cenozoic. Keywords Geological time, Eras, Periods, Precambrian, Palaeozoic, Mesozoic, Cenozoic, Carboniferous, Cambrian , Devonian , Silurian, Quaternary Period, ... twelve periods is further sub-divided into epochs and epoch into ages. It will be observed that the Palaeozoic era begins some 600 million years ago. The ...Cenozoic Era, Third of the major eras of Earth history, and the interval of time during which the continents assumed their modern configurations and geographic positions.The Eocene (IPA: / ˈ iː ə s iː n, ˈ iː oʊ-/ EE-ə-seen, EE-oh-) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period in the modern Cenozoic Era.

To memorize the Epochs of Cenozoic Era: Paleocene, Eocene, Oligocene, Miocene, Pliocene, Pleistocene, Holocene (or Recent): Pretty Eager Old Men Play Poker Hard. Pigeon Egg Omelets Make People Puke Heartily. Put Eggs On My Plate Please Homer. The missing Era: Precambrian.However, the Anthropocene Epoch is an unofficial unit of geologic time, used to describe the most recent period in Earth’s history when human activity started to have a significant impact on the planet’s climate and ecosystems. The word Anthropocene is derived from the Greek words anthropo, for “man,” and cene for “new,” coined and ...The Paleocene, ( IPA: / ˈpæli.əsiːn, - i.oʊ -, ˈpeɪli -/ PAL-ee-ə-seen, -⁠ee-oh-, PAY-lee-) [4] or Palaeocene, is a geological epoch that lasted from about 66 to 56 million years ago (mya). It is the first epoch of the Paleogene Period in the modern Cenozoic Era. The name is a combination of the Ancient Greek παλαιός palaiós ...Aug 29, 2019 · The Precambrian, Paleozoic, Mesozoic, and Cenozoic Eras. The Geologic Time Scale is the history of the Earth broken down into four spans of time marked by various events, such as the emergence of certain species, their evolution, and their extinction, that help distinguish one era from another. Strictly speaking, Precambrian Time is not an ... The Epoch Times is a global media outlet that provides news, opinion, and entertainment from around the world. It is one of the most popular news sources in the world, and its homepage is a great way to stay informed about current events. H...

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Geology Cenozoic era: Facts about climate, animals & plants References By Kim Ann Zimmermann published 9 June 2016 The …The Cenozoic is really the only era divided into epochs because a lot happened in a relatively short amount of time. The Earth cooled drastically and mammals rapidly grew and diversified into all ...Begin with the material that is most likely to fossilize, and finish with the material least likely to fossilize. Label each image with the appropriate relative dating method. Identify the statements that correctly describe the ratio of different stable isotopes of carbon (12C and 13C). - When measured in a tropical paleosol, the ratio of 13C ...The succeeding eon is the Phanerozoic, divided into three eras: the Palaeozoic, an era of arthropods, fishes, and the first life on land; the Mesozoic, which spanned the rise, reign, and climactic extinction of the non-avian dinosaurs; and the Cenozoic, which saw the rise of mammals. Recognizable humans emerged at most 2 million years ago, a ...Quaternary Period, Interval of geologic time, approximately 2.6 million years ago to the present.The Quaternary follows the Neogene Period and is the most recent of the three periods of the Cenozoic Era.The Quaternary is subdivided into the Pleistocene Epoch and the Holocene Epoch and is characterized by major cyclical changes of climate on a …Twitter appears to have officially killed off its legacy blue check marks, one of the last remaining vestiges of the pre-Elon Musk era. Twitter appears to have officially killed off its legacy blue check marks, one of the last remaining ves...

The Quaternary period is the last period of the Cenozoic Era. It is a period known for the many glaciations and glacial retreats. The extinction of huge birds and mammals happened during this period, which left room for the appearance of the human species. The Quaternary period is divided into the Holocene and Pleistocene epochs.quaternary. quat·er·nar·y / ˈkwätərˌnerē / • adj. 1. fourth in order or rank; belonging to the fourth order. 2. (Quaternary) Geol. of, relating to, or denoting the most recent period in the Cenozoic era, following the Tertiary period and comprising the Pleistocene and Holocene epochs (and thus including the present). 3.The Paleogene Period is the first of two periods which make up the Cenozoic Era. ... The Paleogene period, its epochs, the the two Neogene epochs Miocene and ...Although stratigraphers agree upon the names and dates of the Epochs of the Cenozoic, there has historically been considerable disagreement on the Periods of the Cenozoic: American ... Cenozoic is by FAR the best known Era, representing only 1.4 % of Earth History, yet the most commonly encountered rocks on the Earth's surface and on …Beginning 65 million years ago, the Cenozoic’s first of 7 (or possibly 8) epochs was the Paleocene (66-56 Ma). According to the USGS, this 10 million year-long epoch was the time of the diversification of small mammals. As most of the dinosaurs were extinct, new ecological niches opened for the first rodents, primitive primates, and mammalian ...The Cenozoic Era (66 million years ago through today) is the "Age of Mammals." Birds and mammals rose in prominence after the extinction of giant reptiles. Common Cenozoic fossils include cat-like carnivores and early horses, as well as ice age fossils like wooly mammoths. Caves can preserve the remains of ice-age animals that died in them or ...The further subdivision of the eras into 12 "periods" is based on identifiable but less profound changes in life-forms. In the most recent era, the Cenozoic, there is a further subdivision of time into epochs. Follow Nicki on her exploration of the Yemeni island of Socotra to discover one of the most unique-looking places on Earth. Socotra, Yemen's offshore territory gives us a good idea of what Earth looked like before the great Miocene Epoch. T...Africa - Cenozoic, Wildlife, Climate: The Cenozoic, the most recent major interval of geologic time (i.e., the past 66 million years), is commonly divided into the Paleogene, Neogene, and Quaternary periods. The Paleogene and Neogene (about 66 to 2.6 million years ago) are remarkable for their great tectonic movements, which resulted in the Alpine orogeny. During that mountain-building episode ...The Eocene epoch is part of the Tertiary Period in the Cenozoic Era, and lasted from about 54.8 to 33.7 million years ago (mya). The oldest known fossils of most of the modern orders of mammals appear in a brief period during the Early Eocene and all were small, under 10 kg. Both groups of modern ungulates ( Artiodactyla and Perissodactyla ...

Jul 11, 2023 · The group said it had chosen a lake in an Ontario conservation area to represent the start of Anthropocene epoch, ... CENOZOIC ERA 66 million years ago. Dinosaurs appear. 252 million years ago.

Earth Sciences Cenozoic era. The Cenozoic era was the third major epoch of earth's history, beginning approximately 66 million years ago and extending to the present. It was the time interval during which the continents assumed their modern configuration and the different geographical positions they hold to this day, and during which the earth's flora and fauna evolved to the present day. From largest to smallest, this hierarchy includes eons, eras, periods, epochs, and ages. All of these are displayed in the portion of the geologic time scale shown below. Eon: Era: Period: Epoch: Age: Phanerozoic: Cenozoic: Paleogene: ... The Phanerozoic is subdivided into three major divisions: the Cenozoic, Mesozoic, and Paleozoic Eras. The ...Species changed as the epochs of the Cenozoic Era rolled by, with the mammals eventually becoming the largest land animals of the Era, as the dinosaurs had been during the Mesozoic. Flowering plants strongly influenced the evolution of both birds and herbivors throughout the Cenozoic era by providing a rich abundance of food.For the purposes of geology, the “calendar” is the geologic time scale. One way to distinguish and define each segment of time is by the occurrence of major geologic events and the appearance (and disappearance) of significant life-forms, starting with the formation of Earth’s crust followed by the appearance of ever-changing forms of ...Paleogene Period, oldest of the three stratigraphic divisions of the Cenozoic Era spanning the interval between 66 million and 23 million years ago. Paleogene is Greek meaning “ancient-born” and includes the Paleocene (Palaeocene) Epoch (66 million to 56 million years ago), the Eocene Epoch (56Paleogene Period. Learn about the time period that took place 65 to 23 million years ago. At the dawn of the Paleogene—the beginning of the Cenozoic era—dinosaurs, pterosaurs, and giant marine ...Right now, according to the current timeline, we are in — deep breath — the Meghalayan Age of the Holocene Epoch of the Quaternary Period of the Cenozoic Era of the Phanerozoic Eon, and have ...9.Cenozoic Era (65 million years ago to present) The KT Event set the stage for the Cenozoic Era that began 65 million years ago. As the dinosaurs perished at the end of the Cretaceous, the mammals took center stage. It is represented upto present.It is called "Age of Mammals". Even as mammals increased in numbers and diversity, so too did the birds, reptiles, fish, insects, trees, grasses ...The Neogene spans the Miocene and Pliocene epochs, and the Quaternary includes the Pleistocene and Holocene epochs. Geologic processes Cenozoic rocks are extensively developed on all the …

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The last period in the Cenozoic Era was the Quaternary Period that runs from 2.58 million years ago to the present day. During the Pleistocene Epoch. The Holocene Epoch began 11,700 years ago and continues to this day, making it the current epoch of the Quaternary Period of the Cenozoic Era. During most of this time, the climate has been pretty ... That meteorite started a whole new era, scientists propose humans started a new epoch which is a much smaller geologic time period. Geologists measure time in eons, eras, periods, epochs and ages.During the Cenozoic Era, the Paleogene Period is broken up into the Paleocene, Eocene, and Oligocene Epochs. The Neogene Period is broken up into the Miocene and Pliocene Epochs. Each one of these earlier Epochs is marked by important evolutionary and geologic changes that define these bands of time.In turn, epochs are divided into even narrower units of time called ages. For the sake of simplicity, only the epochs of the Paleogene, Neogene, and Quaternary periods are shown on the time scale at the top of this page. It is important to note, however, that all of the periods of the Phanerozoic era are subdivided into the epochs and ages.This article will discuss the Cenozoic era and the epochs within it. We will also discuss the types of animals that evolved and went extinct and how the climate …The Cenozoic Era spans the interval from 66 million years ago to present. It is divided into the Paleogene Period (66–23 million years ago) and Neogene Period (23 million …Geologic time scale Geologic time scale with proportional representation of eons/eonothems and eras/erathems. Cenozoic is abbreviated to Cz. The image also shows some notable events in Earth's history and the general evolution of life. A megannus (Ma) represents one million (10 6) years. The Cenozoic era is divided into three periods: Paleogene period (65-23 million years ago), which consists of the Paleocene, Eocene and Oligocene epochs); Neogene period (23-2.6 million years ago), which includes the Miocene and Pliocene epochs); Quaternary period (2.6 million years ago to the ...The Holocene is part of the Quaternary Period, the most recent division of the Cenozoic Era, which in turn is part of Phanerozoic Eon — which spans from 539 million years ago to the present.We are currently living in the Holocene epoch. The Holocene is a brief flash of time compared to previous epochs and is, in reality, just an interglacial ... ….

Eons are divided into eras, which are further divided into periods, epochs, and ages. Geologic dating is extremely imprecise. For example, although the date listed for the beginning of the Ordovician period is 485 million years ago, it is actually 485.4 with an uncertainty (plus or minus) of 1.9 million years.From hominids, humans evolved in the last 4 million years of the Cenozoic era. 1. The dinosaurs went extinct. Ultimately, the start of the Cenozoic Era was the demise of dinosaurs. After a 6-mile wide asteroid hit Earth 66 million years ago, a dust cloud blocked the sun. It was the Cretaceous–Paleogene (K-Pg) extinction event that wiped out ...Holocene Epoch, younger of the two formally recognized epochs that constitute the Quaternary Period and the latest interval of geologic time, covering approximately the …However, the Anthropocene Epoch is an unofficial unit of geologic time, used to describe the most recent period in Earth’s history when human activity started to have a significant impact on the planet’s climate and ecosystems. The word Anthropocene is derived from the Greek words anthropo, for “man,” and cene for “new,” coined and ...Holocene Epoch, younger of the two formally recognized epochs of the Quaternary Period, covering the most recent 11,700 years of Earth’s history. Holocene sediments cover the largest area of any epoch in the geologic record; the epoch is also coincident with the late and post-Stone Age history of human beings.This marks the start of the Cenozoic Era which continues today. Human-like mammals have only been around for the past 2 million years. However, it has been known that humans have had a greater impact on Earth's history than any other species. #4: A key for your geologic timeline is provided below. When you finish clipping all of your pictures ...The Pleistocene is the last-named epoch of the Cenozoic Era (65 million years ago to the present) and is the first epoch of the Quaternary period, which continues to this day. Climate and Geography The end of the Pleistocene epoch (20,000 to 12,000 years ago) was marked by a global ice age, which led to the extinction of many …The initial epoch of the Paleogene Period and the Cenozoic Era is the Paleocene Epoch, which marks the first subdivision of geologic time after the extinction of the dinosaurs and the end of the Cretaceous Period. In western North America, the uplift of the Rocky Mountains, which started in the Cretaceous, continued throughout the Paleocene.9 de abr. de 2016 ... The Cenozoic Era is sometimes referred to as the Age of Mammals. It was during this stretch of geologic time that the variety of terrestrial ... Cenozoic era epochs, Paleocene Epoch (65-54 mya) The Paleocene epoch marks the beginning of the Cenozoic era and the Tertiary period. Dense forests grow in the warm, damp, and temperate climate., Climate history over the past 500 million years, with the last three major ice ages indicated, Andean-Saharan (450 Ma), Karoo (300 Ma) and Late Cenozoic.A less severe cold period or ice age is shown during the Jurassic-Cretaceous (150 Ma).. There have been five or six major ice ages in the history of Earth over the past 3 billion years. The Late Cenozoic …, The Neogene spans the Miocene and Pliocene epochs, and the Quaternary includes the Pleistocene and Holocene epochs. Geologic processes. Cenozoic rocks are extensively developed on all the continents, particularly on lowland plains, as, for example, the Gulf and Atlantic coastal plains of North America., The climate in the Cenozoic was markedly colder than in the previous Cretaceous. The warming conditions of the prior era produced forests, swamps, and wetlands, ..., Paleocene is the starting Period of the Cenozoic Era and Holocene is the recent one. Cambrian, Ordovician are the Periods of Paleozoic Era not Cenozoic., Pleistocene Epoch, earlier and major of the two epochs of the Quaternary Period of Earth’s history, an epoch during which a succession of glacial and interglacial climatic cycles occurred. It ended 11,700 years ago. It was preceded by the Pliocene Epoch and followed by the Holocene Epoch., The initial epoch of the Paleogene Period and the Cenozoic Era is the Paleocene Epoch, which marks the first subdivision of geologic time after the extinction of the dinosaurs and the end of the Cretaceous Period. In western North America, the uplift of the Rocky Mountains, which started in the Cretaceous, continued throughout the Paleocene., Eons are divided into eras, which are further divided into periods, epochs, and ages. Geologic dating is extremely imprecise. For example, although the date listed for the beginning of the Ordovician period is 485 million years ago, it is actually 485.4 with an uncertainty (plus or minus) of 1.9 million years., divided into Eras which in turn divide into periods, epochs and ages, Largest geological time period...periods of time that total many decades or centuries, Hadean, Archean, Proterozoic, Phanerozoic ... Paleozoic, Mesozoic, Cenozoic, spans millions of years. Epochs. subdivision of geological timescale, shorter than a Period, Longer than an era ..., It is the traditional name for the first of two periods in the Cenozoic Era (66 million years ago to the present); the second is the Quaternary Period (2.6 million years ago to the present)., The Cenozoic Era, the 66.6 million years of earth’s history, holds the evolutionary secrets of all life on earth today. Stacked below the earth’s crust, each layer unfolds stories about the formation of continents, mountains, climatic zones, unimaginable glaciation cycles, the evolution of the mighty Indricotherium, majestic woolly mammoth, and the unbeatable human race from the small ..., The second epoch of the Tertiary Period was referred to as the Eocene Epoch, which spanned the interval between 56 million years and 33.9 million years ago. The early Eocene experienced the highest mean annual temperatures of the Cenozoic Era., During the Cenozoic Era, the Paleogene Period is broken up into the Paleocene, Eocene, and Oligocene Epochs. The Neogene Period is broken up into the Miocene and Pliocene Epochs. Each one of these earlier Epochs is marked by important evolutionary and geologic changes that define these bands of time., Naming of geologic time. 538.8 to 0 million years ago. 538.8. From the Greek words φανερός ( phanerós) meaning 'visible' or 'abundant', and ζωή ( zoē) meaning 'life'., Oct 30, 2012 · Salix sp. leaf. Liquidambar sp. seed pod. The Paleogene Period* is the first of three periods comprising the Cenozoic Era. The Cenozoic, sometimes known as the "Age of Mammals", as the Mesozoic was the "Age of Reptiles", is known by its Epochs. The Paleogene is composed of the first three of these Epochs, (Paleocene, Eocene, and Oligocene Epochs). , Species changed as the epochs of the Cenozoic Era rolled by, with the mammals eventually becoming the largest land animals of the Era, as the dinosaurs had been during the Mesozoic. Flowering plants strongly influenced the evolution of both birds and herbivors throughout the Cenozoic era by providing a rich abundance of food., Paleocene Epoch (65-54 mya) The Paleocene epoch marks the beginning of the Cenozoic era and the Tertiary period. Dense forests grow in the warm, damp, and temperate climate., Jul 11, 2023 · The group said it had chosen a lake in an Ontario conservation area to represent the start of Anthropocene epoch, ... CENOZOIC ERA 66 million years ago. Dinosaurs appear. 252 million years ago. , The primarily defined divisions of time are eons, the Hadean, the Archean, the Proterozoic and the Phanerozoic. The first three of these can be referred to collectively as the Precambrian supereon. Each eon is subsequently divided into eras, which in turn are divided into periods, which are further divided into epochs., An era of geologic time from the beginning of the Tertiary period to the present. Its name is from Greek and means "new life." Quaternary. (1.8 million years ago - Present) The second period of the Cenozoic era. It contains two epochs: the Pleistocene and the Holocene., The second epoch of the Tertiary Period was referred to as the Eocene Epoch, which spanned the interval between 56 million years and 33.9 million years ago. The early Eocene experienced the highest mean annual temperatures of the Cenozoic Era., The oldest of the geological eras is the Eoarchean, which began approximately four billion years ago. The majority of the fossil evidence that we have for primate evolution comes from the Cenozoic era —the current geological era, dating from 65 million year ago (MYA) to the present. The Cenozoic era is divided into a series of epochs., Geologists use epochs to further divide geologic eras and periods. Put the epochs from the Cenozoic Era in chronological order, from the earliest to the most recent. 1. Pliocene 2. Miocene 3. Oligocene 4. Eocene 5. Paleocene. About us. About Quizlet; How Quizlet works; Careers; Advertise with us;, The geological clock: a projection of Earth’s 4,5 Ga history on a clock Author: Woudloper Derivative work: Hardwigg Wikipedia. The Cenozoic Era (also Cænozoic, Caenozoic or Cainozoic; meaning “new life”, from Greek καινός kainos “new”, and ζωή zoe “life”) is the current and most recent of the three Phanerozoic geological eras, following the Mesozoic Era and covering the ..., Progressing from the oldest to the current, the four major eras of Earth’s geological history are Precambrian, Paleozoic, Mesozoic and Cenozoic. The current GTS era, the Cenozoic Era, began 65.5 million years ago., Online exhibits: Geologic time scale: Cenozoic Era Dentary of Viverravus acutus , a small, civet-like Eocene mammal, collected by Malcolm McKenna, Big Horn County, WY, 1950. The Eocene is the second of five epochs in the Tertiary Period — the second of three epochs in the Paleogene — and lasted from about 55.8 to 33.9 million years ago.* , Oct 15, 2023 · This epoch marks the beginning of the Cenozoic era and the tertiary period. The Eocene Epoch (second epoch of the tertiary period) lasted from about 55.8 to 33.9 million years ago. The. Oligocene Epoch (third epoch of the tertiary period) lasted from about 33.9 to 23 million years ago. The Miocene Epoch (fourth epoch of the tertiary period ... , Study with Quizlet and memorize flashcards containing terms like During which of the following do you live? a. The Cenozoic Era b. The Phanerozoic Eon c. The Holocene Epoch d. all of the above, There were so many animals without backbones in the Early Paleozoic that it is often called _____. a. the boneless period b. the vertebrate era c. the …, Cenozoic Era. Following the extinction of the dinosaurs, the Cenozoic ... About: The most recent of all epochs, the Holocene is what we are living in right now., The Cenozoic era, which began 66 million years ago and continues to the present day, has seen the evolution of humans and the development of modern ecosystems. ... From the smallest unit of time, the epoch, to the largest unit, the eon, each division is defined by specific events and changes that took place on Earth. Understanding the …, The Cenozoic Era consists of the following time spans or periods: Paleogene, Neogene, and Quaternary. Paleogene and Neogene were earlier clubbed together as Tertiary, and are still sometimes referred by this name. Paleogene is divided into three epochs – Paleocene, Eocene, Oligocene. Neogene consists of two epochs: Miocene and Pliocene ..., The Cenozoic is divided into three periods: the Paleogene, Neogene, and Quaternary; and seven epochs: the Paleocene, Eocene, Oligocene, Miocene, Pliocene, Pleistocene, and Holocene. The Quaternary Period was officially recognised by the International Commission on Stratigraphy in June 2009. [9], The Eocene epoch is part of the Tertiary Period in the Cenozoic Era, and lasted from about 54.8 to 33.7 million years ago (mya). The oldest known fossils of most of the modern orders of mammals appear in a brief period during the Early Eocene and all were small, under 10 kg. Both groups of modern ungulates ( Artiodactyla and Perissodactyla ...