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The Cenozoic Portal

Introduction

The Cenozoic (/ˌsiːnəˈzoʊ.ɪk, ˌsɛn-/ SEE-nə-ZOH-ik, SEN-ə-; lit. 'new life') is Earth's current geological era, representing the last 66 million years of Earth's history. It is characterized by the dominance of mammals, birds, conifers, and angiosperms (flowering plants). It is the latest of three geological eras, preceded by the Mesozoic and Paleozoic. The Cenozoic started with the Cretaceous–Paleogene extinction event, when many species, including the non-avian dinosaurs, became extinct in an event attributed by most experts to the impact of a large asteroid or other celestial body, the Chicxulub impactor.

The Cenozoic is also known as the Age of Mammals because the terrestrial animals that dominated both hemispheres were mammals – the eutherians (placentals) in the northern hemisphere and the metatherians (marsupials, now mainly restricted to Australia and to some extent South America) in the southern hemisphere. The extinction of many groups allowed mammals and birds to greatly diversify so that large mammals and birds dominated life on Earth. The continents also moved into their current positions during this era.

The climate during the early Cenozoic was warmer than today, particularly during the Paleocene–Eocene Thermal Maximum. However, the Eocene to Oligocene transition and the Quaternary glaciation dried and cooled Earth. (Full article...)

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Selected article on the Cenozoic world and its legacies

Insects, such as this scorpionfly, have a three-part body: head with large compound eyes and antennae, a thorax with three pairs of legs and often wings, and a segmented abdomen.

Insects (from Latin insectum) are hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (head, thorax and abdomen), three pairs of jointed legs, compound eyes, and a pair of antennae. Insects are the most diverse group of animals, with more than a million described species; they represent more than half of all animal species.

The insect nervous system consists of a brain and a ventral nerve cord. Most insects reproduce by laying eggs. Insects breathe air through a system of paired openings along their sides, connected to small tubes that take air directly to the tissues. The blood therefore does not carry oxygen; it is only partly contained in vessels, and some circulates in an open hemocoel. Insect vision is mainly through their compound eyes, with additional small ocelli. Many insects can hear, using tympanal organs, which may be on the legs or other parts of the body. Their sense of smell is via receptors, usually on the antennae and the mouthparts.

Nearly all insects hatch from eggs. Insect growth is constrained by the inelastic exoskeleton, so development involves a series of molts. The immature stages often differ from the adults in structure, habit and habitat. Groups that undergo four-stage metamorphosis often have a nearly immobile pupa. Insects that undergo three-stage metamorphosis lack a pupa, developing through a series of increasingly adult-like nymphal stages. The higher level relationship of the insects is unclear. Fossilized insects of enormous size have been found from the Paleozoic Era, including giant dragonfly-like insects with wingspans of 55 to 70 cm (22 to 28 in). The most diverse insect groups appear to have coevolved with flowering plants.

Adult insects typically move about by walking and flying; some can swim. Insects are the only invertebrates that can achieve sustained powered flight; insect flight evolved just once. Many insects are at least partly aquatic, and have larvae with gills; in some species, the adults too are aquatic. Some species, such as water striders, can walk on the surface of water. Insects are mostly solitary, but some, such as bees, ants and termites, are social and live in large, well-organized colonies. Others, such as earwigs, provide maternal care, guarding their eggs and young. Insects can communicate with each other in a variety of ways. Male moths can sense the pheromones of female moths over great distances. Other species communicate with sounds: crickets stridulate, or rub their wings together, to attract a mate and repel other males. Lampyrid beetles communicate with light.

Humans regard many insects as pests, especially those that damage crops, and attempt to control them using insecticides and other techniques. Others are parasitic, and may act as vectors of diseases. Insect pollinators are essential to the reproduction of many flowering plants and so to their ecosystems. Many insects are ecologically beneficial as predators of pest insects, while a few provide direct economic benefit. Two species in particular are economically important and were domesticated many centuries ago: silkworms for silk and honey bees for honey. Insects are consumed as food in 80% of the world's nations, by people in roughly 3000 ethnic groups. Human activities are having serious effects on insect biodiversity. (Full article...)

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

A pick axe sitting on a wider, protruding rock. Various sized rock prudences are in the photo; most are a little wider than the pick handle. — Outcrop of Ordovician kukersite oil shale, northern Estonia

Oil shale geology is a branch of geologic sciences which studies the formation and composition of oil shales–fine-grained sedimentary rocks containing significant amounts of kerogen, and belonging to the group of sapropel fuels. Oil shale formation takes place in a number of depositional settings and has considerable compositional variation. Oil shales can be classified by their composition (carbonate minerals such as calcite or detrital minerals such as quartz and clays) or by their depositional environment (large lakes, shallow marine, and lagoon/small lake settings). Much of the organic matter in oil shales is of algal origin, but may also include remains of vascular land plants. Three major type of organic matter (macerals) in oil shale are telalginite, lamalginite, and bituminite. Some oil shale deposits also contain metals which include vanadium, zinc, copper, and uranium.

Most oil shale deposits were formed during Middle Cambrian, Early and Middle Ordovician, Late Devonian, Late Jurassic, and Paleogene times through burial by sedimentary loading on top of the algal swamp deposits, resulting in conversion of the organic matter to kerogen by diagenetic processes. The largest deposits are found in the remains of large lakes such as the deposits of the Green River Formation of Wyoming and Utah, USA. Oil-shale deposits formed in the shallow seas of continental shelves generally are much thinner than large lake basin deposits. (Full article...)

Selected images

Image 1Stegotetrabelodon is an extinct genus of primitive elephant with gomphothere-like anatomical features from the Late Miocene to Early Pliocene of Africa and Eurasia
Image 2Fossil tooth of Hyainailurus, an extinct genus of hyaenodont mammal of the family Hyainailouridae that lived during the Miocene
Image 3Palaeotragus ("ancient goat") is a genus of very large, primitive, okapi-like giraffid from the Miocene of Africa, Eurasia.
Image 4Platybelodon ("flat-spear tusk") was a genus of large herbivorous mammals related to the elephant (order Proboscidea). It lived during the late Miocene Epoch in Asia and the Caucasus.
Image 5Victoriapithecus macinnesi was a primate from middle Miocene central Africa
Image 6Prolibytherium ("Before Libya's Beast") is an extinct climacoceratid artiodactyl ungulate native to Early Miocene North Africa and Pakistan
Image 7Mimoperadectes is an extinct genus of didelphimorph marsupial from the Eocene of North America
Image 8Morotopithecus bishopi is a species of fossil ape discovered in Miocene-age deposits of Moroto, Uganda.
Image 9Indarctos is a genus of mammals of the bear family, Ursidae, endemic to North America, Europe and Asia during the Miocene
Image 10Adcrocuta is an extinct genus of terrestrial carnivore in the family Hyaenidae that lived during the Miocene period
Image 11Deinotherium was a large prehistoric relative of modern-day elephants that appeared in the Middle Miocene and survived until the Early Pleistocene
Image 12Proconsul is an extinct genus of primates that existed from 23 to 25 million years ago during the Miocene epoch