Portal:Cretaceous

Topics Culture Geography Health History Mathematics Nature People Philosophy Religion Society Technology The Cretaceous Portal Mounted skeletons at the AMNH. The Cretaceous /krɪˈteɪʃəs/, derived from the Latin "creta" (chalk), usually abbreviated K for its German translation Kreide (chalk), is a geologic period and system from circa 145 ± 4 to 66 ± 0.3 million years (Ma) ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the Cenozoic era. It is the youngest period of the Mesozoic era, and at 80 million years long, the longest period of the Phanerozoic Eon. The end of the Cretaceous defines the boundary between the Mesozoic and Cenozoic eras. In many languages this period is known as "chalk period". The Cretaceous was a period with a relatively warm climate and high eustatic sea level. The oceans and seas were populated with now extinct marine reptiles, ammonites and rudists; and the land by dinosaurs. At the same time, new groups of mammals and birds as well as flowering plants appeared. The Cretaceous ended with one of the largest mass extinctions in Earth history, the K–T extinction, when many species, including non-avian dinosaurs, pterosaurs, and large marine reptiles, disappeared. (see more...) A tunicate is a marine invertebrate animal, a member of the subphylum Tunicata which is part of the Chordata, a phylum which includes all animals with dorsal nerve cords and notochords. Some tunicates live as solitary individuals but others replicate by budding and become colonies, each unit being known as a zooid. They are marine filter feeders with a water-filled, sac-like body structure and two tubular openings, known as siphons, through which they draw in and expel water. During their respiration and feeding they take in water through the incurrent (or inhalant) siphon and expel the filtered water through the excurrent (or exhalant) siphon. Most adult tunicates are sessile and are permanently attached to rocks or other hard surfaces on the ocean floor; others such as salps, doliolids and pyrosomes swim in the pelagic zone of the sea as adults. Various species are commonly known as sea squirts, sea pork, sea liver or sea tulips. The Tunicata first appear in the fossil record in the early Cambrian period. Despite their simple appearance and very different adult form, their close relationship to the vertebrates is shown by the fact that during their mobile larval stage, they possess a notochord or stiffening rod and resemble a tadpole. Their name derives from their unique outer covering or "tunic" which is formed from proteins and carbohydrates and acts as an exoskeleton. In some species it is thin, translucent and gelatinous while in others it is thick, tough and stiff. (see more...) The history of paleontology traces the history of the effort to study the fossil record left behind by ancient life forms. Although fossils had been studied by scholars since ancient times, the nature of fossils and their relationship to life in the past became better understood during the 17th and 18th centuries. At the end of the 18th century the work of Georges Cuvier ended a long running debate about the reality of extinction and led to the emergence of paleontology as a scientific discipline. The first half of the 19th century saw paleontological activity become increasingly well organized. This contributed to a rapid increase in knowledge about the history of life on Earth, and progress towards definition of the geologic time scale. As knowledge of life's history continued to improve, it became increasingly obvious that there had been some kind of successive order to the development of life. After Charles Darwin published Origin of Species in 1859, much of the focus of paleontology shifted to understanding evolutionary paths. The last half of the 19th century saw a tremendous expansion in paleontological activity, especially in North America. The trend continued in the 20th century with additional regions of the Earth being opened to systematic fossil collection, as demonstrated by a series of important discoveries in China near the end of the 20th century. There was also a renewed interest in the Cambrian explosion that saw the development of the body plans of most animal phyla. (see more...) A 95 million year old slab of fossiliferous rock from Hakel, Lebanon measuring 24 cm in width. The specimen prominently preserves a member of the lobster genus Pseudostacus as well as the fish Diplomystus birdii A fragmentary specimen of an additional fish, Dercetis triqueter, is visible in the lower right hand corner of the specimen. Photo credit: Brocken Inaglory File:Cycadeoidea marylandica - National Museum of Natural History - IMG 1978.JPG ... that it is all but impossible to match up species known by leaves with those known by trunks in the prehistoric cycad-like genus Cycadeoidea? ... that a new family of predatory cockroaches, named Manipulatoridae, has been discovered from amber found in the Hukawng Valley of Myanmar? ... that the extinct earwig Toxolabis was preserved with two earwig nymphs? ...that the extinct marine reptile Kaganaias is the only ancient aquatic scaled reptile to be found in Asia? ... that Shantungosuchus, a small, primitive crocodile from the Cretaceous period, was terrestrial instead of aquatic? Template:/box-header 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 Template:/box-footer Template:/box-header Featured Cretaceous articles - Bone Sharps, Cowboys, and Thunder Lizards - Bone Wars - Edward Drinker Cope - Geology of the Capitol Reef area - Geology of the Death Valley area -Geology of the Grand Canyon area - Geology of the Zion and Kolob canyons area Good Cretaceous articles - Chitinozoan - Coal ball - Dimetrodon - History of paleontology - Evolutionary history of life - Ornatifilum - Opabinia - Paleontology- Schinderhannes - Small shelly fauna - Temnospondyli - Tiktaalik - Waptia Template:/box-footer ▼ Cretaceous ► Cretaceous life Here are some tasks awaiting attention: Stubs : Cretaceous stubs Current Cretaceous FACs - none currently Template:/box-footer Time Earth sciences Paleontology Extinct and Endangered Species Paleozoic Triassic Jurassic Cretaceous Cenozoic What are portals? 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