Oligocene Epoch
The Oligocene period is the geologic epoch related to the Paleogene period this extends from about 33.9 million to 23 million years. Like other older geologic periods, the rocks which define the epoch are truly identified but these exact dates of the start and end of the epoch are a little uncertain.
The name Oligocene originated in the year 1854 by a palaeontology must have named Heinrich Ernst Beyrich. His name comes from the Ancient which refers to the extant forms of mollusks. This period is preceded by Eocene Epoch which is then followed by the Miocene Epoch. While Oligocene is the third and also final epoch of the Paleogene Period.
Oligocene Period
Oligocene Period is the third and last major worldwide division of the Paleogene Period which is 65.5 million to about 23 million years ago. This is the interval between 33.9 million to 23 million years ago. The Oligocene Epoch is here subdivided into two ages, we present their corresponding rock stages as well:
The Rupelian Age
The Chattian Age.
This is being followed by the Eocene Epoch and was succeeded by the Miocene Epoch, while the first epoch was the Neogene period. The term used ‘Oligocene’ is being derived from Greek which actually means the “epoch of the few recent forms,” this is being referred to as the sparseness of the number of these modern animals which originated during that time.
In the western part of Europe, the beginning of the Oligocene period was marked by the invasion of the sea which was brought with it by the new mollusks which is a prominent characteristic of the epoch. The marine conditions did not exist in this period for long, however, the brackish and freshwater conditions soon prevailed during this time.
Oligocene Animals
The earliest forms of amphicyonids, canids, tayassuidae, camels, protoceratops, and the anthracotheres showed in this time. Birds like Caprimulgiformes who have gaping mouths to catch the insects also appeared in this period. Diurnal raptors like the falcons, hawks, and eagles with seven to ten families of rodents also originated during the Oligocene Period.
Aluvarus praeimperialis is a type of bony fish, which is extinct, they are known from headless fossil specimens that are found in the Elam Formation.
Oligocene Climate
Oligocene cherished a climate that appeared to have been of a temperate type, there were many regions that enjoyed the subtropical climatic conditions in this region. The grasslands also expanded and the forested regions dwindled in this time. Here the tropical vegetation flourished along the borders of the Sea named Tethyan. Then existed warm, swampy conditions. This specific type of condition prevailed over much of Germany and had extensive deposits of lignite coal.
Oligocene Epoch Animals
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Another prominent group of Oligocene was the marine organisms – foraminiferans, protists. This group was quite similar to amoebas but they bore a complex, and a general calcareous test, or the shell. The prominent foraminiferans were known as the nummulites which were large, lens-shaped foraminiferans. The other marine form is essentially quite modern in approach.
The terrestrial consists of the invertebrate life where abundant and diverse vegetation grew. The deposits of the lake and stream on the Isle of Wight in England also contain the remains, often well preserved. The Baltic and many other forms of Oligocene insects that includes butterflies, bees, ants, and spiders live here in amber.
Oligocene Fossils
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The climatic change occurred approximately 34 million years ago in Africa and not in Asia. More specifically said, the climate marking of the Eocene-Oligocene Transition (this occurred about 34 million years ago) which could have acted as an evolution filter, this allows different types of primates to evolve in the land of Africa while compared to Asia. The ensuing dominance of the subset of primates was known as anthropoids which were located in the African regions, this must-have led to the evolution of humans in this part according to a paper in Science. Even though the early fossils were found in Asia, the actual evolutions of human beings occurred in Africa.
Oligocene Mammals
The Oligocene period marked the advent of large gigantic mammals. Rhinoceroses also reached great heights similar to the animal called Paraceratherium. Dogs and cats were land carnivores animals while dogs and cats were the primary land carnivores and the whales were carnivores at sea. The mammals during the Oligocene period were “Micro-mammals" who experienced a period of diversification. This period was also characterized by free change of animals among the northern continents, as this was seen by the similarity of invertebrate faunas.
Oligocene Plants
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Grasses were the plants that first grew near the water margins in the Eocene after which they became more common in the open habitats. In Northern America the flora also consisted of a mixture of subtropical elements, among others popular were - cashews and lychee trees, also there thrived temperate trees as well such as roses, beech, and pine.Oligocene Epoch Animals
FAQs on Oligocene
1. What is the Oligocene Epoch in the context of Earth's geological history?
The Oligocene Epoch is a significant division of the geologic timescale that occurred from approximately 33.9 to 23 million years ago. It is the third and final epoch of the Paleogene Period within the Cenozoic Era, positioned between the warmer Eocene Epoch and the succeeding Miocene Epoch. The name 'Oligocene' means 'few new things,' referring to the relatively small number of new modern mammal species that appeared compared to the Eocene.
2. What were the major climatic changes that defined the Oligocene Epoch?
The Oligocene was primarily characterized by a significant global cooling trend. This period saw the formation and expansion of the Antarctic ice sheet, which led to a substantial drop in sea levels. As a result, tropical and subtropical forests, which were widespread in the preceding Eocene, began to decline and were replaced by more temperate deciduous forests and vast, open grasslands, especially in the Northern Hemisphere.
3. What types of animals were prominent during the Oligocene?
The Oligocene saw a major diversification of mammals, which began to resemble their modern forms. Key animal groups included:
- Grazing Mammals: The spread of grasslands favoured the evolution of early horses, camels, and rhinos.
- Early Carnivores: Ancestors of modern dogs (canids) and cats (felids) became more common.
- Creodonts and Oreodonts: Archaic groups of carnivores and herbivorous 'ruminating hogs' were still present but began to be replaced by more modern forms.
- Marine Life: Early forms of modern whales, such as toothed whales (odontocetes), and sharks evolved and diversified.
4. What makes the Oligocene Epoch a critical transitional period in Earth's history?
The Oligocene is considered a critical transitional period because it acts as a bridge between the archaic, tropical world of the Eocene and the more modern-looking ecosystems of the Miocene. The shift from a 'greenhouse' to an 'icehouse' climate triggered fundamental changes in flora and fauna. This forced a major evolutionary shift from animals adapted to forests to those suited for open plains and grasslands, setting the stage for the evolution of many modern mammal lineages.
5. How did the expansion of grasslands during the Oligocene influence animal evolution?
The global expansion of grasslands created new ecosystems and evolutionary pressures. This directly influenced animal evolution in several ways:
- Dietary Changes: Animals developed tougher, high-crowned teeth to cope with abrasive grasses.
- Locomotion: Life on open plains favoured the evolution of longer legs for running, both for predators to hunt and for prey to escape.
- Social Behaviour: Herding behaviour became an effective defence mechanism for grazing animals in open environments.
6. What important geological events occurred during the Oligocene Epoch?
Significant geological events during the Oligocene reshaped the planet's geography and climate. Key events include the continued separation of continents, most notably Australia and South America drifting away from Antarctica. This created the Antarctic Circumpolar Current, which isolated Antarctica and was a major driver of its glaciation. Additionally, major mountain-building events (orogenies), such as the continued uplift of the Alps and the Rocky Mountains, were active during this epoch.
7. What led to the end of the Oligocene Epoch?
The end of the Oligocene Epoch around 23 million years ago was not marked by a single mass extinction event but rather a gradual transition into the Miocene Epoch. The primary drivers were continued long-term climate fluctuations and the resulting ecological competition. As new, more adaptable species of grazers, browsers, and predators evolved and spread, they outcompeted many of the remaining archaic Oligocene fauna, leading to a turnover in dominant species and the start of a new geological epoch.
