Cretaceous period 145. 5 - 65. 5 million years ago ↓ PЄ Є O S D C P T J K PG N
Mean atmospheric O2 content over period duration	ca. The Precambrian ( Pre-Cambrian) is an informal name for the supereon comprising the eons of the Geologic timescale that came before the current The Cambrian is a geologic period and system that began about Ma (million years ago at the end of the Proterozoic eon and ended about Ma with The Ordovician is a geologic period and system, the second of six of the Paleozoic era, and covers the time between 488 The Silurian is a geologic period and system that extends from the end of the Ordovician period about 443 The Devonian is a geologic period and system of the Paleozoic era spanning from to  million years ago. The Carboniferous is a geologic period and system that extends from the end of the Devonian period about 359 The Permian is a geologic period and system that extends from 299 The Triassic is a geologic period and system that extends from about 251 to 199 Ma (million years ago The Jurassic is a geologic period and system that extends from about Ma (million years ago to  Ma that is from the end of the Triassic to the beginning The Paleogene (alternatively Palaeogene) is a geologic period and system that began 65 The Neogene is a geologic period and system starting 2303 ± 0 Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the 30 Vol %[1] (150 % of modern level)
Mean atmospheric CO2 content over period duration	ca. Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single 1700 ppm[2] (6 times pre-industrial level)
Mean surface temperature over period duration	ca. "Parts-per" notation is used especially in Science and Engineering, to denote Ratios (relative proportions in measured quantities particularly 18°C [3] (4°C above modern level)
Key events in the Cretaceous view • discuss • edit -140 — – -130 — – -120 — – -110 — – -100 — – -90 — – -80 — – -70 — – Maastrichtian Campanian Santonian Coniacian Turonian Cenomanian Albian Aptian Barremian Hauterivian Valanginian Berriasian Jurassic Paleogene             C r e t a c e o u s  Mesozoic  Cenozoic An approximate timescale of key Cretaceous events. The Maastrichtian is the last stage of the Cretaceous period, and therefore of the Mesozoic era. The Campanian is a stage on the Geologic time scale occurring from 83 The Santonian is a Faunal stage of the Late Cretaceous Epoch. The Coniacian is a stage of the Late Cretaceous Epoch. It spans the time between 89 The Turonian is a stage of the Late Cretaceous Epoch. It spans the time between 93 |-|The Cenomanian age (also known as Woodbinian by the [[ICS]] is the first or earliest or oldest Geochronological "geologic age" Albian ( French Albion, from Alba = Aube in France) is a stage of the Cretaceous period. Aptian stage is a Faunal stage of the Early Cretaceous epoch in the Geologic timescale, that extends from 125 The Barremian Faunal stage was a period of geological time between 130 The Hauterivian is a stage of the Early Cretaceous Epoch. It spans the time between 136 In the Geologic timescale, Valanginian is a stage of the Early Cretaceous epoch. In the Geologic timescale, Berriasian is a stage of the Early Cretaceous epoch, and the first of the entire Cretaceous period The Jurassic is a geologic period and system that extends from about Ma (million years ago to  Ma that is from the end of the Triassic to the beginning The Paleogene (alternatively Palaeogene) is a geologic period and system that began 65 The Mesozoic Era is one of three geologic eras of the Phanerozoic eon. The Cenozoic (also Caenozoic or Cainozoic) Era (ˌsiːnəˈzoʊɪk/ /ˌsɛn- (meaning "new life" ( Greek ( kainos) "new" Axis scale: millions of years ago.

The Cretaceous (pronounced /kriːˈteɪʃəs/, usually abbreviated 'K' for its German translation "Kreide") is a geological period, reaching from the end of the Jurassic Period, (145.5 ± 4 million years ago (Ma) to the beginning of the Paleocene Period, 65.5 ± 0. The Jurassic is a geologic period and system that extends from about Ma (million years ago to  Ma that is from the end of the Triassic to the beginning The Paleocene or Palaeocene, "early dawn of the recent" is a geologic epoch that lasted from 65 3 Ma. It is the youngest geological period of the Mesozoic, and at 80 million years long, the longest period of the Phanerozoic. The Mesozoic Era is one of three geologic eras of the Phanerozoic eon. The Phanerozoic (occasionally Phanaerozoic) Eon is the current eon in the Geologic timescale, and the one during which abundant animal life has existed The end of the Cretaceous defines the boundary between the Mesozoic and Cenozoic eras. The Cenozoic (also Caenozoic or Cainozoic) Era (ˌsiːnəˈzoʊɪk/ /ˌsɛn- (meaning "new life" ( Greek ( kainos) "new"

The Cretaceous (from Latin creta meaning 'chalk' ^[4]) as a separate period was first defined by a Belgian geologist Jean d'Omalius d'Halloy in 1822, using strata in the Paris Basin^[5] and named for the extensive beds of chalk (calcium carbonate deposited by the shells of marine invertebrates, principally coccoliths), found in the upper Cretaceous of continental Europe and the British Isles (including the White Cliffs of Dover). Latin ( lingua Latīna, laˈtiːna is an Italic language, historically spoken in Latium and Ancient Rome. Chalk (ʧɔːk is a soft white porous Sedimentary rock, a form of Limestone composed of the Mineral Calcite. Jean Baptiste Julien d'Omalius d'Halloy (1783-1875 was a Belgian Geologist. In Geology and related fields a stratum (plural strata) is a layer of rock or Soil with internally consistent characteristics that distinguishes The Paris Basin is one of the major geological regions of France having developed since the Triassic on a basement formed by the Variscan orogeny. Calcium carbonate is a Chemical compound with the Chemical formula Ca[[Carbon C]] O 3 An invertebrate is an Animal lacking a Vertebral column. The group includes 98% of all animal Species — all animals except those in the Chordate Coccoliths are individual plates of Calcium carbonate formed by Coccolithophores (single-celled algae such as Emiliania huxleyi The British Isles (Irish variously Na hOileáin Bhriotanacha, Oileáin Iarthair Eorpa, Éire agus an Bhreatain Mhór; Ellanyn Goaldagh Eileanan The white cliffs of Dover are Cliffs which form part of the British coastline facing the Strait of Dover and France.

Dating

As with other older geologic periods, the rock beds that define the Cretaceous are well identified but the exact dates of the period's start and end are uncertain by a few million years. No great extinction or burst of diversity separated the Cretaceous from the Jurassic. In Biology and Ecology, extinction is the cessation of existence of a Species or group of taxa. However, the end of the period is most sharply defined, being placed at an iridium-rich layer found worldwide that is believed to be associated with the Chicxulub impact crater in Yucatan and the Gulf of Mexico. Iridium (ɪˈrɪdiəm is a Chemical element that has the symbol Ir and Atomic number 77 The Chicxulub Crater (tʃikʃuˈlub is an ancient Impact crater buried underneath the Yucatán Peninsula in Mexico. Yucatán is one of the 31 states of Mexico, located on the north of the Yucatán Peninsula. The Gulf of Mexico ( Spanish: Golfo de México) is the ninth largest Body of water in the world This layer has been tightly dated at 65. 5 Ma. This bolide collision is probably responsible for the major, extensively-studied Cretaceous–Tertiary extinction event. The Cretaceous–Tertiary extinction event, which occurred approximately ( Ma) was a large-scale mass extinction of animal and plant species in a geologically

Divisions

The Cretaceous is usually separated into Early and Late Cretaceous Epochs. The Early Cretaceous ( timestratigraphic name or the Lower Cretaceous ( logstratigraphic name is the earlier of the two major divisions of the Cretaceous Late Cretaceous (100mya - 65mya refers to the second half of the Cretaceous Period, named after the famous white Chalk cliffs of southern England The geologic time scale is a chronologic schema (or idealized Model) relating Stratigraphy to time that is used by Geologists and other The faunal stages from youngest to oldest are listed below; time is referred to as early or late, and the corresponding rocks are referred to as lower or upper:

Paleogeography

During the Cretaceous, the late Paleozoic - early Mesozoic supercontinent of Pangaea completed its breakup into present day continents, although their positions were substantially different at the time. The Paleozoic or Palaeozoic Era (from the Greek palaio (παλαιο "old" and zoe (ζωη "life" meaning "ancient life" In Geology, a supercontinent is a Landmass comprising more than one Continental core or Craton. Pangaea, Pangæa or Pangea (pænˈdʒiːə from παν pan, meaning entire, and Γαῖα Gaea, meaning Earth in A continent is one of several large Landmasses on Earth. They are generally identified by Convention rather than any strict criteria with seven regions As the Atlantic Ocean widened, the convergent-margin orogenies that had begun during the Jurassic continued in the North American Cordillera, as the Nevadan orogeny was followed by the Sevier and Laramide orogenies. Orogeny (Greek for "mountain generating" is the process of natural Mountain building and may be studied as a tectonic structural event as a geographical event and The American cordillera consists of an essentially continuous sequence of Mountain ranges that form the western "backbone" of North America, Central The Nevadan Orogeny was a major Mountain building event that took place along the western edge of ancient North America between the Mid to Late Jurassic The Sevier orogeny was a mountain-building event that affected western North America from Canada to the north to Mexico to the south The Laramide orogeny was a period of Mountain building in western North America, which started in the Late Cretaceous, 70 to 80 million years ago and ended

Geography of the US in the Late Cretaceous Period

Though Gondwana was still intact in the beginning of the Cretaceous, it broke up as South America, Antarctica and Australia rifted away from Africa (though India and Madagascar remained attached to each other); thus, the South Atlantic and Indian Oceans were newly formed. Gondwana (ɡɒnˈdwɑːnə originally Gondwanaland) was a southern Supercontinent that existed about 500 to 200 Ma ago South America is a Continent of the Americas, situated entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a For a topic outline on this subject see List of basic Australia topics. India, officially the Republic of India (भारत गणराज्य inc-Latn Bhārat Gaṇarājya; see also other Indian languages) is a country Madagascar, or Republic of Madagascar (older name Malagasy Republic) is an Island nation in the Indian Ocean off the southeastern The Indian Ocean is the third largest of the world's Oceanic divisions covering about 20% of the water on the Earth 's surface Such active rifting lifted great undersea mountain chains along the welts, raising eustatic sea levels worldwide. Mean sea level (MSL is the average (mean height of the Sea, with reference to a suitable reference surface To the north of Africa the Tethys Sea continued to narrow. The Tethys Ocean was a Mesozoic era Ocean that existed between the continents of Gondwana and Laurasia before the opening of the Indian Broad shallow seas advanced across central North America (the Western Interior Seaway) and Europe, then receded late in the period, leaving thick marine deposits sandwiched between coal beds. The Western Interior Seaway, also called the Cretaceous Seaway, the Niobraran Sea, and the North American Inland Sea, was a huge inland Sea At the peak of the Cretaceous transgression, one-third of Earth's present land area was submerged. A transgression is a geologic event during which Sea level rises relative to the land and the shoreline moves toward higher ground resulting in flooding ^[6]

The Cretaceous is justly famous for its chalk; indeed, more chalk formed in the Cretaceous than in any other period in the Phanerozoic. Chalk (ʧɔːk is a soft white porous Sedimentary rock, a form of Limestone composed of the Mineral Calcite. The Phanerozoic (occasionally Phanaerozoic) Eon is the current eon in the Geologic timescale, and the one during which abundant animal life has existed ^[7] Mid-ocean ridge activity — or rather, the circulation of seawater through the enlarged ridges — enriched the oceans in calcium; this made the oceans more saturated, as well as increased the bioavailability of the element for calcareous nanoplankton. A mid-ocean ridge or mid-oceanic ridge is an underwater Mountain range typically having a valley known as a Rift running along its axis formed by Coccolithophores (also called coccolithophorids) are single-celled Algae, Protists and Phytoplankton belonging to the Division ^[8] These widespread carbonates and other sedimentary deposits make the Cretaceous rock record especially fine. In Chemistry, a carbonate is a salt or Ester of Carbonic acid. Sedimentary rock is one of the three main rock types (the others being igneous and Metamorphic rock) Famous formations from North America include the rich marine fossils of Kansas's Smoky Hill Chalk Member and the terrestrial fauna of the late Cretaceous Hell Creek Formation. Kansas ( is a Midwestern state in the central region of the United States of America, an area often referred to as the American " The Hell Creek Formation is an intensely-studied division of Upper Cretaceous to lower Paleocene rocks in North America named for exposures studied along Hell Other important Cretaceous exposures occur in Europe (e. g. , the Weald) and China (the Yixian Formation). The Weald (wɪəld is the name given to a physiographic area in south-east England situated between the parallel Chalk Escarpments of the North China ( Wade-Giles ( Mandarin) Chung¹kuo² is a cultural region, an ancient Civilization, and depending on perspective a National The Yixian Formation is a Geological formation in Jinzhou, Liaoning, People's Republic of China, that stems from the Early Cretaceous In the area that is now India, massive lava beds called the Deccan Traps were erupted in the very late Cretaceous and early Paleocene. The Deccan Traps are a Large igneous province located on the Deccan Plateau of west-central India (between 17-24N 73-74E and one of the largest Volcanic

Climate

The Berriasian epoch showed a cooling trend that had been seen in the last epoch of the Jurassic. In the Geologic timescale, Berriasian is a stage of the Early Cretaceous epoch, and the first of the entire Cretaceous period There is evidence that snowfalls were common in the higher latitudes and the tropics became wetter than during the Triassic and Jurassic^[9]. Glaciation was however restricted to alpine glaciers on some high-latitude mountains, though seasonal snow may have existed further south. "Glacial" and "Glaciation" redirect here For the geological periods see Glacial period. Latitude, usually denoted symbolically by the Greek letter phi ( Φ) gives the location of a place on Earth (or other planetary body north or south of the

After the end of the Berriasian, however, temperatures increased again, and these conditions were almost constant until the end of the period^[10]. This trend was due to intense volcanic activity which produced large quantities of carbon dioxide. Plate tectonics and hotspots Divergent plate boundaries At the Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single The development of a number of mantle plumes across the widening mid-ocean ridges further pushed sea levels up, so that large areas of the continental crust were covered with shallow seas. A mantle plume is an upwelling of abnormally hot rock within the Earth's mantle. A mid-ocean ridge or mid-oceanic ridge is an underwater Mountain range typically having a valley known as a Rift running along its axis formed by The Tethys Sea connecting the tropical oceans east to west also helped in warming the global climate. The Tethys Ocean was a Mesozoic era Ocean that existed between the continents of Gondwana and Laurasia before the opening of the Indian Warm-adapted plant fossils are known from localities as far north as Alaska and Greenland, while dinosaur fossils have been found within 15 degrees of the Cretaceous south pole. Paleobotany, also spelled as palaeobotany (from the Greek words paleon = old and " Botany " study of plants is the branch of Alaska ( Аляска Alyaska) is a state in the United States of America, in the northwest of the North American continent Greenland (Kalaallit Nunaat meaning "Land of the Greenlanders" Grønland is a self-governing Danish Province located between the The South Pole, also known as the Geographic South Pole or Terrestrial South Pole, is the southernmost point on the surface of the Earth. ^[11]

A very gentle temperature gradient from the equator to the poles meant weaker global winds, contributing to less upwelling and more stagnant oceans than today. In atmospheric sciences ( Meteorology, Climatology and related fields the temperature gradient (typically of air, more generally of any Fluid The equator (sometimes referred to colloquially as "the Line") is the intersection of the Earth 's surface with the plane perpendicular to the Upwelling is an oceanographic phenomenon that involves wind-driven motion of dense cooler and usually nutrient-rich water towards the ocean surface replacing the warmer An ocean (from Greek, ''Okeanos'' (Oceanus) is a major body of saline water, and a principal component of the Hydrosphere. This is evidenced by widespread black shale deposition and frequent anoxic events. Shale (also called mudstone) is a fine-grained Sedimentary rock whose original constituents were Clay minerals or Muds It is characterized by Oceanic anoxic events or Anoxic events occur when the Earth 's Oceans become completely depleted of oxygen (O2 below the surface levels ^[12] Sediment cores show that tropical sea surface temperatures may have briefly been as warm as 42 °C (107 °F), 17 °C (31 °F) warmer than at present, and that they averaged around 37 °C (99 °F). Meanwhile deep ocean temperatures were as much as 15 to 20 °C (27 to 36 °F) higher than today's. ^[13][14]

Further information: Cool tropics paradox

Life

Plants

Flowering plants (angiosperms) spread during this period, although they did not become predominant until the Campanian stage near the end of the epoch. The cool tropics paradox refers to an apparent difference between modelled estimates of tropical Temperatures during warm ice-free periods of the Cretaceous The flowering plants or angiosperms ( Angiospermae or Magnoliophyta) are the most widespread group The Campanian is a stage on the Geologic time scale occurring from 83 Their evolution was aided by the appearance of bees; in fact angiosperms and insects are a good example of coevolution. Bees are flying Insects closely related to Wasps and Ants Bees are a Monophyletic lineage within the superfamily Apoidea In a broad sense biological co-evolution is "the change of a biological object triggered by the change of a related object" The first representatives of many leafy trees, including figs, planes and magnolias, appeared in the Cretaceous. Ficus is a Genus of about 850 Species of woody Trees Shrubs Vines Epiphytes and hemi-epiphytes in the family Platanus is a small genus of Trees native to the Northern Hemisphere. Magnolia is a large Genus of about 210 Flowering plant Species in the subclass Magnolioideae of the family At the same time, some earlier Mesozoic gymnosperms like Conifers continued to thrive; pehuéns (Monkey Puzzle trees, Araucaria) and other conifers being notably plentiful and widespread, although other gymnosperm taxa like Bennettitales died out before the end of the period. Gymnosperm (Gymnospermae are a group of Spermatophyte seed-bearing Plants with Ovules on the edge or blade of an open Sporophyll, which are Araucaria is a Genus of Evergreen coniferous Trees in the family Araucariaceae. Bennettitales (the cycadeoids) is an extinct order of seed plants that first appeared in the Triassic period and became extinct toward

Terrestrial fauna

Tyrannosaurus rex, one of the largest land predators of all time lived during the late Cretaceous. Tyrannosaurus ( or, meaning 'tyrant lizard' is a Genus of Theropod Dinosaur.

A pterosaur, Anhanguera piscator

On land, mammals were a small and still relatively minor component of the fauna. For other meanings see Pterodactyl (disambiguation. Pterosaurs (ˈtɛrəsɔr from the Greek πτερόσαυρος pterosauros Anhanguera (meaning "old devil" is a genus of pterodactyloid Pterosaur known from the Lower- Cretaceous ( Aptian) Santana Formation Mammals ( class Mammalia) are a class of Vertebrate Animals characterized by the presence of Sweat glands, including sweat glands Fauna is all of the Animal life of any particular region or time The fauna was dominated by archosaurian reptiles, especially dinosaurs, which were at their most diverse. Archosaurs ( Greek for 'ruling lizards' are a group of Diapsid Reptiles represented by Modern birds and Crocodilians This group also Reptiles, or members of the class Reptilia are air-breathing Cold-blooded Vertebrates that have skin covered in scales as opposed to hair or feathers Pterosaurs were common in the early and middle Cretaceous, but as the Cretaceous proceeded they faced growing competition from the adaptive radiation of birds, and by the end of the period only two highly specialised families remained. For other meanings see Pterodactyl (disambiguation. Pterosaurs (ˈtɛrəsɔr from the Greek πτερόσαυρος pterosauros An adaptive radiation is a rapid Evolutionary radiation characterized by an increase in the morphological and ecological diversity of a single rapidly diversifying lineage Birds ( class Aves) are bipedal endothermic ( Warm-blooded) Vertebrate animals that lay eggs. In Biological classification, family ( Latin

The Liaoning lagerstätte (Chaomidianzi formation) in China provides a glimpse of life in the Early Cretaceous, where preserved remains of numerous types of small dinosaurs, birds, and mammals have been found. ( is a northeastern province of the People's Republic of China. A Lagerstätte ( German; literally place of storage; plural Lagerstätten) is a sedimentary deposit that exhibits extraordinary fossil The coelurosaur dinosaurs found there represent types of the group maniraptora, which is transitional between dinosaurs and birds, and are notable for the presence of hair-like feathers. For the prehistoric gliding reptile see Coelurosauravus. Coelurosauria (sɨˌljʊərəˈsɔriə is defined as the clade containing all Theropod Maniraptora ("hand snatchers" is a Clade of Coelurosaurian Dinosaurs which includes the Birds and the dinosaurs that were more closely Feathers are one of the epidermal growths that form the distinctive outer covering or Plumage, on Birds They are considered the most complex integumentary structures

During the Cretaceous, insects began to diversify, and the oldest known ants, termites and some lepidopterans, akin to butterflies and moths, appeared. Insects ( Class Insecta) are a major group of Arthropods and the most diverse group of Animals on the Earth with over a million described Ants are social Insects of the family Formicidae and along with the related families of Wasps and Bees belong to the order The termites are a group of Social Insects usually classified at the taxonomic rank of order Isoptera (but see also taxonomy Lepidoptera is an order of Insect that includes Moths and butterflies. A butterfly is an Insect of the order Lepidoptera. Like all Lepidoptera butterflies are notable for their unusual life cycle with a Aphids, grasshoppers, and gall wasps appeared. Grasshoppers are Insects of the suborder Caelifera in the order Orthoptera. Gall wasps (Cynipidae also called Gallflies are a family of the order Hymenoptera and are classified with the Apocrita suborder of wasps in the superfamily

Marine fauna

In the seas, rays, modern sharks and teleosts became common. Batoidea is a Superorder of cartilaginous fish containing more than 500 described species in thirteen families Sharks ( Superorder Selachimorpha) are a type of Fish with a full cartilaginous Skeleton and a highly streamlined body Teleostei is one of three infraclasses in class Actinopterygii, the ray-finned fishes Marine reptiles included ichthyosaurs in the early and middle of the Cretaceous, plesiosaurs throughout the entire period, and mosasaurs in the Late Cretaceous. Ichthyosaurs ( Greek for 'fish lizard' - ιχθυς / ichthyos meaning 'fish' and σαυρος / sauros meaning 'lizard' were giant Plesiosaurs (ˈpliːziəˌsɔɹ ( Greek: plesios/πλησιος meaning 'near' or 'close to' and sauros/σαυρος meaning Mosasaurs (from Latin Mosa meaning the ' Meuse river ' in the Netherlands and Greek sauros meaning 'lizard' were serpentine marine

Baculites, a genus of straight-shelled form of ammonite, flourished in the seas. Baculites ("walking stick rock" is a Genus of extinct marine animals in the Phylum Mollusca and Class Ammonites are an extinct group of marine animals of the subclass Ammonoidea in the class Cephalopoda phylum The Hesperornithiformes were flightless, marine diving birds that swam like grebes. Hesperornithes is an extinct and highly specialized Clade of Cretaceous toothed Birds Hesperornithine birds apparently limited to former aquatic habitats Grebes are members of the Podicipediformes order, a widely distributed order of freshwater diving birds some of which visit the sea when migrating Globotruncanid Foraminifera and echinoderms such as sea urchins and starfish (sea stars) thrived. The Foraminifera, ("Hole Bearers" or forams for short are a large group of Amoeboid Protists with reticulating Pseudopods fine Echinoderms (Phylum Echinodermata) are a phylum of marine Animals (including Sea stars) Starfish (also called sea stars) are any Echinoderms belonging to the class Asteroidea. The first radiation of the diatoms (generally siliceous, rather than calcareous) in the oceans occurred during the Cretaceous; freshwater diatoms did not appear until the Miocene. Diatoms ( Greek: (dia = "through" + (temnein = "to cut" i The Chemical compound silicon dioxide, also known as silica or silox (from the Latin " Silex " is an Oxide Calcareous refers to a Sediment, Sedimentary rock, or Soil type which is formed from or contains a high proportion of Calcium carbonate in the The Miocene is a geological epoch of the Neogene period and extends from about 23 The Cretaceous was also an important interval in the evolution of bioerosion, the production of borings and scrapings in rocks, hardgrounds and shells (Taylor and Wilson, 2003). Bioerosion describes the Erosion of hard ocean substrates by living organisms by a number of mechanisms Carbonate hardgrounds are surfaces of synsedimentarily cemented carbonate layers that have been exposed on the seafloor (Wilson and Palmer 1992

Extinction

Main article: Cretaceous–Tertiary extinction event

There was a progressive decline in biodiversity during the Maastrichtian stage of the Cretaceous Period prior to the suggested ecological crisis induced by events at the K-T boundary. The Cretaceous–Tertiary extinction event, which occurred approximately ( Ma) was a large-scale mass extinction of animal and plant species in a geologically Biodiversity is the variation of Life forms within a given Ecosystem, Biome or for the entire Earth. An ecological crisis occurs when the environment of a Species or a Population changes in a way that destabilizes its continued survival The K-T boundary is a geological signature usually a thin band dated to 65 Furthermore, biodiversity required a substantial amount of time to recover from the K-T event, despite the probable existence of an abundance of vacant ecological niches. In Ecology, a niche (pronounced nich nēsh or nish A shorthand definition of niche is how an organism makes a living ^[15]

Despite the severity of this boundary event, there was significant variability in the rate of extinction between and within different clades. A clade is a taxonomic group comprising a single Common ancestor and all the descendants of that ancestor Species which depended on photosynthesis declined or became extinct because of the reduction in solar energy reaching the earth's surface due to atmospheric particles blocking the sunlight. Photosynthesis is a Metabolic pathway that converts Light Energy into Chemical energy. Solar energy is the Light and radiant heat from the Sun that powers Earth 's Climate and Weather and sustains Life As is the case today, photosynthesizing organisms, such as phytoplankton and land plants, formed the primary part of the food chain in the late Cretaceous. Phytoplankton are the Autotrophic component of the Plankton community Plants are living Organisms belonging to the kingdom Plantae. Food chains, also called food networks and/or trophic networks, describe the feeding relationships between species within an Ecosystem. Evidence suggests that herbivorous animals, which depended on plants and plankton as their food, died out as their food sources became scarce; consequently, top predators such as Tyrannosaurus rex also perished. Herbivory is a form of Predation in which an Organism, known as a herbivore, consumes principally Autotrophs ref name=Campbell>Campbell Tyrannosaurus ( or, meaning 'tyrant lizard' is a Genus of Theropod Dinosaur. ^[16]

Coccolithophorids and molluscs, including ammonites, rudists, freshwater snails and mussels, as well as organisms whose food chain included these shell builders, became extinct or suffered heavy losses. Coccolithophores (also called coccolithophorids) are single-celled Algae, Protists and Phytoplankton belonging to the Division Molluscs are animals belonging to the phylum Mollusca. There are around 250000 extant Species within the phylum with an estimated 70000 Ammonites are an extinct group of marine animals of the subclass Ammonoidea in the class Cephalopoda phylum Rudists are a group of bizarrely shaped marine Heterodont Bivalves that arose during the Jurassic, and became so diverse during the The word snail is a Common name that can be used for almost all members of the Molluscan class Gastropoda which have coiled shells in the The common name mussel is used for members of several different families of Clams or Bivalve Molluscs, from both saltwater and freshwater habitats Food chains, also called food networks and/or trophic networks, describe the feeding relationships between species within an Ecosystem. For example, it is thought that ammonites were the principal food of mosasaurs, a group of giant marine reptiles that became extinct at the boundary. Mosasaurs (from Latin Mosa meaning the ' Meuse river ' in the Netherlands and Greek sauros meaning 'lizard' were serpentine marine ^[17]

Omnivores, insectivores and carrion-eaters survived the extinction event, perhaps because of the increased availability of their food sources. Omnivores (from Latin omne all everything vorare to devour are species that eat both Plants and Animals as their primary An insectivore is a type of carnivore with a diet that consists chiefly of Insects and similar small creatures Carrion (from the Latin caro, meaning meat refers to the carcass of a dead animal At the end of the Cretaceous there seem to have been no purely herbivorous or carnivorous mammals. A carnivore (ˈkɑrnɪvɔər meaning 'meat eater' ( Latin carne meaning 'flesh' and vorare meaning 'to devour' is any animal with a diet consisting Mammals ( class Mammalia) are a class of Vertebrate Animals characterized by the presence of Sweat glands, including sweat glands Mammals and birds which survived the extinction fed on insects, larvae, worms, and snails, which in turn fed on dead plant and animal matter. Insects ( Class Insecta) are a major group of Arthropods and the most diverse group of Animals on the Earth with over a million described A larva ( Latin; plural larvae) is a juvenile form of Animal with indirect development, undergoing Metamorphosis (for example A worm is a common name given to a diverse group of invertebrate animals that have a long soft body and no legs Scientists theorise that these organisms survived the collapse of plant-based food chains because they fed on detritus. In Biology, detritus is non-living particulate organic material (as opposed to dissolved organic material ^[18][15][19]

In stream communities, few groups of animals became extinct. A stream is a body of Water with a current, confined within a bed and stream-banks A biocoenosis (alternatively biocoenose or biocenose) termed by Karl Möbius in 1877 describes all the interacting Organisms living together Stream communities rely less on food from living plants and more on detritus that washes in from land. This particular ecological niche buffered them from extinction. ^[20] Similar, but more complex patterns have been found in the oceans. Extinction was more severe among animals living in the water column, than among animals living on or in the sea floor. Any water in the sea that is not close to the bottom is in the pelagic zone. Animals in the water column are almost entirely dependent on primary production from living phytoplankton, while animals living on or in the ocean floor feed on detritus or can switch to detritus feeding. See also Primary production (economics Primary production is the production of Organic compounds from atmospheric or aquatic Carbon dioxide, "Ocean Floor" redirects here For the 2001 song by Audio Adrenaline, see Lift (Audio Adrenaline album. ^[15]

The largest air-breathing survivors of the event, crocodilians and champsosaurs, were semi-aquatic and had access to detritus. Crocodilia is an order of large Reptiles that appeared about 84 million years ago in the late Cretaceous Period ( Campanian stage Choristodera is an order of semi-aquatic Diapsid Reptiles which ranged from the Middle Jurassic, or possibly Late Triassic, to Modern crocodilians can live as scavengers and can survive for months without food, and their young are small, grow slowly, and feed largely on invertebrates and dead organisms or fragments of organisms for their first few years. These characteristics have been linked to crocodilian survival at the end of the Cretaceous. ^[18]

Numerous borings in a Cretaceous cobble, Faringdon, England; these are excellent examples of fossil bioerosion. Bioerosion describes the Erosion of hard ocean substrates by living organisms by a number of mechanisms

Cretaceous hardground from Texas with encrusting oysters and borings. Carbonate hardgrounds are surfaces of synsedimentarily cemented carbonate layers that have been exposed on the seafloor (Wilson and Palmer 1992 Texas ( is a state geographically located in the South Central United States and is also known as the Lone Star State. The common name oyster is used for a number of different groups of Bivalve Mollusks most of which live in marine habitats or Brackish water. The scale bar is 1. 0 cm.

See also

• Chalk Formation
• List of fossil sites (with link directory)
• Western Interior Seaway

References

• Kashiyama, Yuichiro; Nanako O. The Chalk Formations of Europe are thick deposits of Chalk, a soft porous white Limestone, deposited in a marine environment during the upper Cretaceous This is a worldwide list of important and/or well-known localities where Fossils have been found The Western Interior Seaway, also called the Cretaceous Seaway, the Niobraran Sea, and the North American Inland Sea, was a huge inland Sea Ogawa, Junichiro Kuroda, Motoo Shiro, Shinya Nomoto, Ryuji Tada, Hiroshi Kitazato, Naohiko Ohkouchi (2008-05). "Diazotrophic cyanobacteria as the major photoautotrophs during mid-Cretaceous oceanic anoxic events: Nitrogen and carbon isotopic evidence from sedimentary porphyrin". Organic Geochemistry 39 (5): 532-549. doi:10.1016/j.orggeochem.2007.11.010. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.  
• Neal L Larson, Steven D Jorgensen, Robert A Farrar and Peter L Larson. Ammonites and the other Cephalopods of the Pierre Seaway. Geoscience Press, 1997.
• Ogg, Jim; June, 2004, Overview of Global Boundary Stratotype Sections and Points (GSSP's) http://www.stratigraphy.org/gssp.htm Accessed April 30, 2006.
• Ovechkina, M. N. and Alekseev, A. S. 2005. Quantitative changes of calcareous nannoflora in the Saratov region (Russian Platform) during the late Maastrichtian warming event. Journal of Iberian Geology 31 (1): 149-165. PDF
• Rasnitsyn, A.P. and Quicke, D. Alexandr (Alex P Rasnitsyn (born 24 September 1936 in Moscow) is one of the world's leading experts in Palaeoentomology. L. J. (2002). History of Insects. Kluwer Academic Publishers. Springer Science+Business Media or Springer (ˈʃpʁɪŋɐ is a worldwide Publishing company based in Germany, which publishes textbooks academic ISBN 1-4020-0026-X.   — detailed coverage of various aspects of the evolutionary history of the insects.
• Skinner, Brian J. , and Stephen C. Porter. The Dynamic Earth: An Introduction to Physical Geology. 3rd ed. New York: John Wiley & Sons, Inc. , 1995. ISBN 0-471-60618-9}
• Stanley, Steven M. Earth System History. New York: W. H. Freeman and Company, 1999. ISBN 0-7167-2882-6
• Taylor, P. D. and Wilson, M. A. , 2003. Palaeoecology and evolution of marine hard substrate communities. Earth-Science Reviews 62: 1-103. [1]

Notes

External links

• UCMP Berkeley Cretaceous page
• Bioerosion website at The College of Wooster