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Portal:Cretaceous

The Cretaceous Portal

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Introduction

The Cretaceous ( /krɪˈtʃəs/, kri-TAY-shəs) is a geologic period and system that spans 79 million years from the end of the Jurassic Period 145 million years ago (mya) to the beginning of the Paleogene Period 66 mya. It is the last period of the Mesozoic Era, and the longest period of the Phanerozoic Eon. The Cretaceous Period is usually abbreviated K, for its German translation Kreide (chalk, creta in Latin).

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. During this time, new groups of mammals and birds, as well as flowering plants, appeared.

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Ordovician bryozoans.
The Bryozoa are a phylum of aquatic invertebrate animals. Typically about 0.5 millimetres (0.020 in) long, they are filter feeders that sieve food particles out of the water using a retractable lophophore, a "crown" of tentacles lined with cilia. Individuals in bryozoan colonies are called zooids, since they are not fully independent animals. All colonies contain autozooids, which are responsible for feeding and excretion. Colonies of some classes have various types of non-feeding specialist zooids. Zooids consist of a cystid that provides the body wall and produces the exoskeleton and a polypide that contains the internal organs and the lophophore or other specialist extensions. Colonies take a variety of forms, including fans, bushes and sheets.

Mineralized skeletons of bryozoans first appear in rocks from Early Ordovician period, making it the last major phylum to appear in the fossil record. This has led researchers to suspect that bryozoans had arisen earlier but were initially unmineralized, and may have differed significantly from fossilized and modern forms. Early fossils are mainly of erect forms, but encrusting forms gradually became dominant. It is uncertain whether the phylum is monophyletic. Bryozoans' evolutionary relationships to other phyla are also unclear, partly because scientists' view of the family tree of animals is mainly influenced by better-known phyla. Both morphological and molecular phylogeny analyses disagree over bryozoans' relationships with entoprocts, about whether bryozoans should be grouped with brachiopods and phoronids in Lophophorata, and whether bryozoans should be considered protostomes or deuterostomes. (see more...)

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Laelaps by Charles R. Knight.

The painting Laelaps by Charles R. Knight depicts two Dryptosaurus fighting.
Photo credit: User:Crotalus horridus

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

Jurassic Park author Michael Crichton.

Jurassic Park is a 1993 American science fiction adventure film directed by Steven Spielberg. It is the first installment of the Jurassic Park franchise. It is based on the 1990 novel of the same name by Michael Crichton, with a screenplay written by Crichton and David Koepp. The film centers on the fictional Isla Nublar, an islet located off Central America's Pacific Coast, near Costa Rica Nicaragua border, where a billionaire philanthropist and a small team of genetic scientists have created a wildlife park of cloned dinosaurs.

Following an extensive $65 million marketing campaign, which included licensing deals with 100 companies, Jurassic Park grossed over $900 million worldwide in its original theatrical run. It surpassed Spielberg's 1982 film E.T. the Extra-Terrestrial to become the highest-grossing film until Titanic (1997). Jurassic Park was well received by critics, who praised its special effects and Spielberg's direction but criticized the script. The film won more than 20 awards (including 3 Academy Awards), mostly for its visual effects. Jurassic Park is considered by many to be one of the greatest films of the 1990s and in some cases of all time, as well as a landmark in the vector of visual effects regarding its computer-generated imagery and animatronics.

Jurassic Park was followed by two sequels, The Lost World: Jurassic Park and Jurassic Park III, both of which were box office successes but received mixed critical responses. A third sequel, Jurassic World, is set for release on June 12, 2015. (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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