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The Paleogene Portal

Introduction

The Paleogene Period (IPA: /ˈpeɪli.ədʒiːn, -li.oʊ-, ˈpæli-/ PAY-lee-ə-jeen, -⁠lee-oh-, PAL-ee-; also spelled Palaeogene or Palæogene) is a geologic period and system that spans 43 million years from the end of the Cretaceous Period 66 Ma (million years ago) to the beginning of the Neogene Period 23.03 Ma. It is the first period of the Cenozoic Era and is divided into the Paleocene, Eocene, and Oligocene epochs. The earlier term Tertiary Period was used to define the time now covered by the Paleogene Period and subsequent Neogene Period; despite no longer being recognized as a formal stratigraphic term, "Tertiary" still sometimes remains in informal use. Paleogene is often abbreviated "Pg", although the United States Geological Survey uses the abbreviation "Pe" for the Paleogene on the Survey's geologic maps.

During the Paleogene period, mammals continued to diversify from relatively small, simple forms into a large group of diverse animals in the wake of the Cretaceous–Paleogene extinction event that ended the preceding Cretaceous Period. (Full article...)

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Selected article on the Paleogene world and its legacies

A fungus (/ˈfʌŋɡəs/; plural: fungi) is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants and animals. One major difference is that fungal cells have cell walls that contain chitin, unlike the cell walls of plants and some protists, which contain cellulose. These and other differences show that the fungi form a single group of related organisms, named the Eumycota. The discipline of biology devoted to the study of fungi is known as mycology. Genetic studies have shown that fungi are more closely related to animals than to plants.

Abundant worldwide, most fungi are inconspicuous because of the small size of their structures, and their cryptic lifestyles in soil, on dead matter, and as symbionts of plants, animals, or other fungi. They may become noticeable when fruiting, either as mushrooms or molds. Fungi perform an essential role in the decomposition of organic matter and have fundamental roles in nutrient cycling and exchange. However, little is known of the true biodiversity of Kingdom Fungi, which has been estimated at 1.5 million to 5 million species. Phylogenetic studies published in the last decade have helped reshape the classification of Kingdom Fungi, which is divided into one subkingdom, seven phyla, and ten subphyla. A group of all the fungi present in a particular area or geographic region is known as mycobiota. (see more...)

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Did you know?

... that the recently described extinct penguin Inkayacu from the Eocene of Peru is postulated to have had gray and reddish brown feathers, unlike the black and white feathers of living penguins?
... that at just over 18 millimetres (0.71 in), Fibla carpenteri is the largest species of snakefly known from amber?
... that unlike other Eocene crocodilians found in Zamora, Spain, the extinct genus Duerosuchus was primarily a fish eater?
... that Archiinocellia is noted to be the only snakefly fossil genus from British Columbia and one of only two from Canada?
... that a fossil of the extinct monitor lizard Saniwa preserves cartilage, scales, and even a wind pipe?

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Life restoration of Paraceratherium transouralicum.
Image credit: Dmitry Bogdanov

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Selected article on the Paleogene in human science, culture and economics

Evolutionary thought, the conception that species change over time, has roots in antiquity. With the beginnings of biological taxonomy in the late 17th century, a new anti-Aristotelian approach to modern science challenged traditional essentialism. Naturalists began to focus on the variability of species; the emergence of paleontology with the concept of extinction further undermined the static view of nature. In the early 19th century, Jean-Baptiste Lamarck proposed the first fully formed theory of evolution.

In 1858, Charles Darwin and Alfred Russel Wallace published a new evolutionary theory that was explained in detail in Darwin's On the Origin of Species (1859). Unlike Lamarck, Darwin proposedcommon descent and a branching tree of life. The theory was based on the idea of natural selection, and it synthesized a broad range of evidence from animal husbandry, biogeography, geology, morphology, and embryology.

The debate over Darwin's work led to the rapid acceptance of the general concept of evolution, but the specific mechanism he proposed, natural selection, was not widely accepted until it was revived by developments in biology that occurred during the 1920s through the 1940s. Before that time most biologists argued that other factors were responsible for evolution. The synthesis of natural selection with Mendelian genetics during the 1920s and 1930s founded the new discipline of population genetics. Throughout the 1930s and 1940s, population genetics became integrated with other biological fields, resulting in a widely applicable theory of evolution that encompassed much of biology—the modern evolutionary synthesis. (see more...)

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