The Cretaceous period is one of the major divisions of the geologic timescale, reaching from the end of the Jurassic period, about 146 million years ago (Ma), to the beginning of the Paleocene epoch of the Tertiary period (65.5 Ma). The end of the Cretaceous also defines the boundary between the Mesozoic and Cenozoic eras. Cretaceous - Name and dating. As with other older geologic periods, the rock beds that define the Cretaceous are well identified, but the exact dates of the pe ...

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Cretaceous - Name and dating Cretaceous - Divisions Cretaceous - Paleogeography Cretaceous - Flora Cretaceous - Fauna
Cretaceous - Land animals Cretaceous - Marine animals Cretaceous - Extinction
Cretaceous - References and further reading

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Cretaceous - Land animals. On land, mammals were a small and still relatively minor component of the fauna. The fauna was dominated by archosaurian reptiles, especially dinosaurs, which were at their most diverse. Pterosaurs were common in the early and middle Cretaceous, but as the Cretaceous proceeded faced growing competition from the adaptive radiation of birds, and by the end of the period only two h ...

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Cretaceous, Cretaceous - Name and dating, Cretaceous - Divisions, Cretaceous - Paleogeography, Cretaceous - Flora, Cretaceous - Fauna, Cretaceous - Land animals, Cretaceous - Marine animals, Cretaceous - Extinction, Cretaceous - References and further reading

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The Cretaceous-Tertiary (K-T or KT) extinction event, also known as the KT boundary, was a period of massive extinction of species, about 65.5 million years ago. It corresponds to the end of the Cretaceous Period and the beginning of the Tertiary Period. (K is the traditional abbreviation for the Cretaceous period. Cretaceous comes from the Latin for chalk, creta. The K comes from the German word for chalk kreide, or possibly Greek kreta. The K is used so as ...

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Cretaceous-Tertiary extinction event - Casualties of the extinction Cretaceous-Tertiary extinction event - Theories
Cretaceous-Tertiary extinction event - Alvarez hypothesis Cretaceous-Tertiary extinction event - Chicxulub crater Cretaceous-Tertiary extinction event - Deccan traps Cretaceous-Tertiary extinction event - Multiple impact event Cretaceous-Tertiary extinction event - Supernova hypothesis
Cretaceous-Tertiary extinction event - Further skepticism Cretaceous-Tertiary extinction event - Other mass extinctions

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An anoxic event occurs when the Earth's oceans become completely depleted of O2 below the surface levels. Anoxic event - Occurrence. Anoxic events occur only during periods of very warm climate characterised by high levels of CO2, usually above 1800 ppmv, and mean surface temperatures of around 22 ° C (Quaternary levels are 280 ppmv and 13 ° C). Thus, anoxic events have been concentrated in the Paleogene, Cretaceous and Jurassic, when numoerous ones have been documented ...

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Anoxic event - Occurrence Anoxic event - Major anoxic events in the Cretaceous Anoxic event - Mechanism Anoxic event - Consequences

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The Cenozoic Era (sen-oh-ZOH-ik; sometimes Caenozoic Era in the United Kingdom) meaning "new life" (Greek kaino = new + zoikos = life) is the most recent of the four classic geological eras. It covers the 65.5 million years since the Cretaceous-Tertiary extinction event at the end of the Cretaceous that marked the demise of the last dinosaurs and the end of the Mesozoic Era. The Cenozoic era is ongoing. The Cenozoic is divided into two periods, the Palaeogene and Neogene, and they are in turn divided into e ...

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Cenozoic - References and further reading

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A wide range of organisms became extinct at the end of the Cretaceous period. The most conspicuous, of course, were the dinosaurs. While there is evidence that dinosaur diversity declined in the Late Cretaceous of North America, many species are known from the Hell Creek and Lance Formations of the Late Cretaceous. These include six or seven families of theropods and a similar number of ornithischians. Among the Dinosauria, the only survivors were the birds, but birds suffered heavy losses. A number of diverse groups became extinct, includin ...

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Cretaceous-Tertiary extinction event, Cretaceous-Tertiary extinction event - Casualties of the extinction, Cretaceous-Tertiary extinction event - Theories, Cretaceous-Tertiary extinction event - Alvarez hypothesis, Cretaceous-Tertiary extinction event - Chicxulub crater, Cretaceous-Tertiary extinction event - Deccan traps, Cretaceous-Tertiary extinction event - Multiple impact event, Cretaceous-Tertiary extinction event - Supernova hypothesis, Cretaceous-Tertiary extinction event - Further skepticism, Cretaceous-Tertiary extinction event - Other mass extinctions

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Conservation status: Fossil The Ceratopsia (the name is Greek for "horned face") are a group of herbivorous, beaked dinosaurs which thrived in North America and Asia during the Cretaceous. They include the bipedal Psittacosauridae, (some of which bore elaborate, porcupine-like spines), and the quadrupedal Protoceratopsidae and Ceratopsidae, characterized by horns and frills. The frills may have begun as sites for muscle attachment, to ...

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Agathis Araucaria Wollemia The Araucariaceae are a very ancient family of conifers. They achieved maximum diversity in the Jurassic and Cretaceous periods, when they existed almost worldwide. At the end of the Cretaceous, when dinosaurs became extinct, so too did the Araucariaceae in the northern hemisphere. There are three genera with 41 species alive today, Agathis, Araucaria and Wollemia, all derived from the Antarctic flora and distributed largely in the southern hemisphere. By ...

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Coeluridae is a family of generally small, carnivorous dinosaurs from the Jurassic and Cretaceous periods. For many years, any small Jurassic or Cretaceous theropod that did not belong to one of the more specialized families recognized at the time was classified with the coelurids, creating a confusing array of "coelurid" theropods that were not closely related. Some dinosaurs mistakenly assigned to Coeluridae in the past include Stenonychosaurus (a troodontid) and Microvenator (a close relative of oviraptorids).

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The Barremian faunal stage was a period of geological time between 117 Ma and 113 Ma (million years ago). It is considered to be of the lower Cretaceous period. Other related archivesCretaceous, Ma, faunal stage

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The Western Interior Seaway, also called the Cretaceous Seaway and the North American Inland Sea, was a huge inland sea that split the continent of North America into two halves during most of the early and mid-Cretaceous period. The Seaway was created as the Pacific and North American tectonic plates collided, causing the Rocky Mountains to form in western North America. With high eustatic sea levels obtaining worldwide during the Cretaceous, cold water from the Arctic Ocean in the north and warm water from the G ...

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Albian (French Albion, from Alba = Aube in France) Albian is a stage of the Cretaceous period. Albian is a term proposed in 1842 by A. d'Orbigny for that stage of the Cretaceous system which comes above (later) the Aptian and below (before) the Cenomanian (Pal. France. Cret. ii.). Approximate time range is 112.0 ± 1.0 Ma to 99.6 ± 0.9 Ma (million years ago). The following representatives of the Albian stage are worthy of notice: the gaize and phosphatic beds of Argonne and Bray in France; the Flammenmergel of North Germany; the lignites of Iltrillas in Spain; the Upper Sandstones of Nubia, ...

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Cycadeoidaceae Williamsoniaceae Bennettitales is an order of seed plants in the anthophyte clade that first appeared in the Triassic period and became extinct toward the end of the Cretaceous. It comprises two groups, cycadeoids, which had stout trunks and bisporangiate strobili (cones serving as their reproductive structures), and relatives of Williamsonia and Williamsoniella, which had slender, branching trunks a ...

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Conservation status: Fossil A. huinculensis Argentinosaurus was a herbivorous sauropod dinosaur that is quite possibly the largest, heaviest land animal that ever lived. It developed on the island continent of South America during the Cretaceous period, after all of its more familiar Laurasian Jurassic kin — like Apatosaurus — had long disappeared. Argentinosaurus - Description. Not much of Argentinosaurus has been recovered: ...

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Argentinosaurus - Description Argentinosaurus - Classification and history

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Conservation status: Fossil Ankylosauridae Nodosauridae The Ankylosauria, less formally known as the ankylosaurians, were a group of ornithischian ("bird-hipped") dinosaurs that lived in the late Cretaceous period. They are characterised by bony plates, which protected them against predators. There have been found on every continent except Africa. The first dinosaur ever discovered in Antarctica w ...

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In the geologic timescale, Valanginian is a stage of the Lower Cretaceous epoch. It spanned between 140.2 Ma and 136.4 Ma (million years ago). The Valanginian stage succeeds the Berriasian stage of the Lower Cretaceous and precedes the Hauterivian stage of the Lower Cretaceous. Other related archivesBerriasian, Hauterivian, Lower Cretaceous, Ma, geologic timescale, stage

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In the geologic timescale, Berriasian is a stage of the Lower Cretaceous epoch. It spanned between 145.5 Ma and 140.2 Ma (million years ago). The Berriasian stage succeeds the Tithonian stage of the Upper Jurassic epoch and precedes the Valanginian stage of the Lower Cretaceous epoch. Other related archivesLower Cretaceous, Ma, Tithonian, Upper Jurassic, Valanginian, epoch, geologic timescale, stage

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The Cimolodonta are a taxon of extinct mammals that lived from the Cretaceous to the Eocene. They were some of the more derived members of the extinct order Multituberculata. They probably lived something of a rodent-like existence until their ecological niche was assumed by true rodents. The more basal multituberculates are found in a different suborder, "Plagiaulacida". Cimolodonta is apparently a natural (monophyletic) suborder. Remains have been identified from across the Northern Hemisphere. The taxon is recognized as the ...

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The Cenomanian (also known as Woodbinian) is the first stage of the Late Cretaceous Epoch. It spans the time between 99.6 ± 0.9 Ma and 93.5 ± 0.8 Ma (million years ago). Other related archivesEpoch, Late Cretaceous, Ma, stage

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