Portal:Cretaceous

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The Cretaceous Portal

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Introduction

The Cretaceous ( /krɪˈt.ʃəs/, krih-TAY-shəs) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic era, as well as the longest. At nearly 80 million years, it is the longest geological period of the entire Phanerozoic. The name is derived from the Latin creta, " chalk", which is abundant in the latter half of the period. It is usually abbreviated K, for its German translation Kreide.

The Cretaceous was a period with a relatively warm climate, resulting in high eustatic sea levels that created numerous shallow inland seas. These oceans and seas were populated with now- extinct marine reptiles, ammonites, and rudists, while dinosaurs continued to dominate on land. The world was ice free, and forests extended to the poles. During this time, new groups of mammals and birds appeared. During the Early Cretaceous, flowering plants appeared and began to rapidly diversify, becoming the dominant group of plants across the Earth by the end of the Cretaceous, coincident with the decline and extinction of previously widespread gymnosperm groups. ( Full article...)

Selected article on the Cretaceous world and its legacies

Skull of Carnotaurus sastrei.
Carnotaurus is a genus of large theropod dinosaur that lived in South America during the Late Cretaceous period, between about 72 and 70 million years ago. The only species is Carnotaurus sastrei. Known from a single well-preserved skeleton, it is one of the best-understood theropods from the Southern Hemisphere. The skeleton, found in 1984, was uncovered in the Chubut Province of Argentina from rocks of the La Colonia Formation. Carnotaurus is a derived member of the Abelisauridae, a group of large theropods that occupied the large predatorial niche in the southern Landmasses of Gondwana during the late Cretaceous.

Carnotaurus was a lightly built, bipedal predator, measuring 8 to 9 m (26 to 30 ft) in length and weighing at least 1 metric ton (0.98 long tons; 1.1 short tons). The skeleton is preserved with extensive skin impressions, showing a mosaic of small, non-overlapping scales. The mosaic was interrupted by large bumps that lined the sides of the animal, and there are no hints of feathers. The distinctive horns and the muscular neck may have been used in fighting conspecifics. The feeding habits of Carnotaurus remain unclear: some studies suggest the animal was able to hunt down very large prey such as sauropods, while other studies find it preyed mainly on relatively small animals. Carnotaurus was well adapted for running and was possibly one of the fastest large theropods. ( see more...)

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Fossil of the Late Cretaceous ammonoid Pachydiscus duelmensis

A fossil shell of the pachydiscid ammonoid Pachydiscus duelmensis. The shell dates back to the Campanian age (72.1–83.6 million years ago) of the Late Cretaceous epoch and is about 20 cm in diameter. It was collected near Dülmen, Germany and is exhibited in the Museum für Naturkunde in Berlin.
Photo credit: H. Zell

Selected article on the Cretaceous in human science, culture or economics

Photograph of Edward Drinker Cope
Edward Drinker Cope (July 28, 1840 – April 12, 1897) was an American paleontologist and comparative anatomist, as well as a noted herpetologist and ichthyologist. Cope distinguished himself as a child prodigy, publishing his first scientific paper at the age of nineteen. Cope later married and moved from Philadelphia to Haddonfield, New Jersey, although Cope would maintain a residence and museum in Philadelphia in his later years.

Cope had little formal scientific training, and he eschewed a teaching position for field work. He made regular trips to the American West prospecting in the 1870s and 1880s, often as a member of United States Geological Survey teams. A personal feud between Cope and paleontologist Othniel Charles Marsh led to a period of intense fossil-finding competition now known as the Bone Wars. Cope's financial fortunes soured after failed mining ventures in the 1880s. He experienced a resurgence in his career toward the end of his life before dying in 1897.

Cope's scientific pursuits nearly bankrupted him, but his contributions helped to define the field of American paleontology. He was a prodigious writer, with 1,400 papers published over his lifetime, although his rivals would debate the accuracy of his rapidly published works. He discovered, described, and named more than 1,000 vertebrate species including hundreds of fishes and dozens of dinosaurs. His proposals on the origin of mammalian molars and for the gradual enlargement of mammalian species over geologic time (" Cope's Law") are notable among his theoretical contributions. ( see more...)

Geochronology

Epochs - Early Cretaceous - Late Cretaceous
Stages - Berriasian - Valanginian - Hauterivian - Barremian - Aptian - Albian - Cenomanian - Turonian - Coniacian - Santonian - Campanian - Maastrichtian
Events - Cambrian–Ordovician extinction event - Great Ordovician Biodiversification Event - Taconic orogeny - Late Ordovician glaciation - Alice Springs Orogeny - Ordovician–Silurian extinction event

Landmasses - Baltica - Gondwana - Laurentia - Siberia
Bodies of water - Iapetus Ocean - Khanty Ocean - Proto-Tethys Ocean - Rheic Ocean - Tornquist Sea - Ural Ocean
Animals - Articulate brachiopods - Bryozoans - Cornulitids - Crinoids - Cystoids - Gastropods - Graptolites - Jawed fishes - Nautiloids - Ostracoderms - Rugose corals - Star fishes - Tabulate corals - Tentaculitids - Trilobites
Trace fossils - Petroxestes - Trypanites
Plants - Marchantiophyta

Fossil sites - Beecher's Trilobite Bed - Walcott–Rust quarry
Stratigraphic units - Chazy Formation - Fezouata formation - Holston Formation - Kope Formation - Potsdam Sandstone - St. Peter Sandstone

Researchers - Charles Emerson Beecher - Charles Lapworth - Charles Doolittle Walcott
Culture - Animal Armageddon - List of creatures in the Walking with... series - Sea Monsters

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