Cretaceous

The impact of a meteorite or comet is today widely accepted as the main reason for the Cretaceous–Paleogene extinction event.
Drawing of fossil jaws of Mosasaurus hoffmanni, from the Maastrichtian of Dutch Limburg, by Dutch geologist Pieter Harting (1866)
Scipionyx, a theropod dinosaur from the Early Cretaceous of Italy
Map of North America During the Late Cretaceous
A computer-simulated model of surface conditions in Middle Cretaceous, 100 mya, displaying the approximate shoreline and calculated isotherms
Facsimile of a fossil of Archaefructus from the Yixian Formation, China
Derasmosaurus pietraroiae, a rhyncocephalian from the late Early Cretaceous of Italy
Philydrosaurus, a choristodere from the Early Cretaceous of China
Tyrannosaurus rex, one of the largest land predators of all time, lived during the Late Cretaceous
Up to 2 m long and 0.5 m high at the hip, Velociraptor was feathered and roamed the Late Cretaceous
Triceratops, one of the most recognizable genera of the Cretaceous
The azhdarchid Quetzalcoatlus, one of the largest animals to ever fly, lived during the Late Cretaceous
Confuciusornis, a genus of crow-sized birds from the Early Cretaceous
Ichthyornis was a toothed, seabird-like ornithuran from the Late Cretaceous
A scene from the early Cretaceous: a Woolungasaurus is attacked by a Kronosaurus.
Tylosaurus was a large mosasaur, carnivorous marine reptiles that emerged in the late Cretaceous.
Strong-swimming and toothed predatory waterbird Hesperornis roamed late Cretacean oceans.
The ammonite Discoscaphites iris, Owl Creek Formation (Upper Cretaceous), Ripley, Mississippi
A plate with Nematonotus sp., Pseudostacus sp. and a partial Dercetis triqueter, found in Hakel, Lebanon
Cretoxyrhina, one of the largest Cretaceous sharks, attacking a Pteranodon in the Western Interior Seaway

Geological period that lasted from about 145 to 66 million years ago .

- Cretaceous
The impact of a meteorite or comet is today widely accepted as the main reason for the Cretaceous–Paleogene extinction event.

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Dinosaur

Dinosaurs are a diverse group of reptiles of the clade Dinosauria.

Dinosaurs are a diverse group of reptiles of the clade Dinosauria.

Birds are avian dinosaurs, and in phylogenetic taxonomy are included in the group Dinosauria.
Triceratops skeleton, Natural History Museum of Los Angeles County
Labeled diagram of a typical archosaur skull, the skull of Dromaeosaurus
Hip joints and hindlimb postures of: (left to right) typical reptiles (sprawling), dinosaurs and mammals (erect), and rauisuchians (pillar-erect)
William Buckland
Sir Richard Owen's coining of the word dinosaur, at a meeting of the British Association for the Advancement of Science in 1841
Paleontologist Robert T. Bakker with mounted skeleton of a tyrannosaurid (Gorgosaurus libratus)
Scipionyx fossil with intestines, Natural History Museum of Milan
The early dinosaurs Herrerasaurus (large), Eoraptor (small) and a Plateosaurus skull, from the Triassic
The supercontinent Pangaea in the early Mesozoic (around 200 million years ago)
Restoration of six dromaeosaurid theropods: from left to right Microraptor, Velociraptor, Austroraptor, Dromaeosaurus, Utahraptor, and Deinonychus
Restoration of four macronarian sauropods: from left to right Camarasaurus, Brachiosaurus, Giraffatitan, and Euhelopus
Restoration of six ornithopods; far left: Camptosaurus, left: Iguanodon, center background: Shantungosaurus, center foreground: Dryosaurus, right: Corythosaurus, far right (large) Tenontosaurus.
Comparative size of Argentinosaurus to the average human
An adult bee hummingbird, the smallest known dinosaur
A nesting ground of the hadrosaur Maiasaura peeblesorum was discovered in 1978
Restoration of two Centrosaurus apertus engaged in intra-specific combat
Restoration of a striking and unusual visual display in a Lambeosaurus magnicristatus
Nest of a plover (Charadrius)
Fossil interpreted as a nesting oviraptorid Citipati at the American Museum of Natural History. Smaller fossil far right showing inside one of the eggs.
This 1897 restoration of Brontosaurus as an aquatic, tail-dragging animal, by Charles R. Knight, typified early views on dinosaur lifestyles.
Comparison between the air sacs of an abelisaur and a bird
Various feathered non-avian dinosaurs, including Archaeopteryx, Anchiornis, Microraptor and Zhenyuanlong
Pneumatopores on the left ilium of Aerosteon riocoloradensis
The Chicxulub Crater at the tip of the Yucatán Peninsula; the impactor that formed this crater may have caused the dinosaur extinction.
Outdated Iguanodon statues created by Benjamin Waterhouse Hawkins for the Crystal Palace Park in 1853
The battles that may have occurred between Tyrannosaurus and Triceratops are a recurring theme in popular science and dinosaurs' depiction in culture

They became the dominant terrestrial vertebrates after the Triassic–Jurassic extinction event 201.3 mya; their dominance continued throughout the Jurassic and Cretaceous periods.

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Geologic time scale

Representation of time based on the rock record of Earth.

Representation of time based on the rock record of Earth.

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Graphical representation of Earth's history as a spiral
Geologic time scale with proportional representation of eons/eonothems and eras/erathems. Cenozoic is abbreviated to Cz. The image also shows some notable events in Earth's history and the general evolution of life.

For example, the Cretaceous–Paleogene extinction event, marks the lower boundary of the Paleogene System/Period and thus the boundary between the Cretaceous and Paleogene Systems/Periods.

Pterosaur

Pterosaurs ( from Greek pteron and sauros, meaning "wing lizard") were flying reptiles of the extinct clade or order Pterosauria.

Pterosaurs ( from Greek pteron and sauros, meaning "wing lizard") were flying reptiles of the extinct clade or order Pterosauria.

Conical tooth, possibly from Coloborhynchus
Reconstruction of crests: three crested tapegyarids. From top to bottom: Tapejara wellnhoferi, Tupandactylus navigans, Tupandactylus imperator (drawn to scale)
The skull of Thalassodromeus
A neck vertebra of Arambourgiania
The neck of Anhanguera was longer than the torso
The shoulder girdle connected to the notarium
Reconstructed wing planform of Quetzalcoatlus northropi (A) compared to the wandering albatross Diomedea exulans (B) and the Andean condor Vultur gryphus (C). These are not to scale; the wingspan of Q. northropi was more than three times as long as that of the wandering albatross.
Some specimens, such as this Rhamphorhynchus, preserve the membrane structure
Sordes, as depicted here, evidences the possibility that pterosaurs had a cruropatagium – a membrane connecting the legs that, unlike the chiropteran uropatagium, leaves the tail free
An anhanguerid pelvis seen from above, with the right side rotated towards the viewer
Sordes preserved pycnofibers
Jeholopterus
Engraving of the original Pterodactylus antiquus specimen by Egid Verhelst II, 1784
Newman's marsupial pterosaurs
Seeley's dynamical Dimorphodon reconstruction
This drawing of Zhejiangopterus by John Conway exemplifies the "new look" of pterosaurs
The three-dimensionally preserved skull of Anhanguera santanae, from the Santana Formation, Brazil
Life restoration of Sharovipteryx, a gliding "protorosaur" which some controversial studies have posited as a close relative of pterosaurs.
Life restoration of Scleromochlus, an archosauromorph theorized to be related to pterosaurs.
Life restoration of Lagerpeton, lagerpetids share many anatomical and neuroanatomical similarities with pterosaurs.
The skeleton of a pterosaur on display in the Arizona Museum of Natural History in Mesa Arizona.
Diagrams showing breathing motion (top two) and internal air sac system (bottom two)
Pterosaur flight adaptations.
Skeletal reconstruction of a quadrupedally launching Pteranodon longiceps
The probable Azhdarchid trace fossil Haenamichnus uhangriensis.
The fossil trackways show that pterosaurs like Hatzegopteryx were quadrupeds, and some rather efficient terrestrial predators.
Fossil pterodactyloid juvenile from the Solnhofen Limestone
Quetzalcoatlus models in South Bank, created by Mark Witton for the Royal Society's 350th anniversary
Scene from When Dinosaurs Ruled the Earth depicting an outsized Rhamphorhynchus

They existed during most of the Mesozoic: from the Late Triassic to the end of the Cretaceous (228 to 66 million years ago ).

Badlands near Drumheller, Alberta, Canada, where glacial and post-glacial erosion have exposed the K–Pg boundary along with much other sedimentation (the exact boundary is a thin line not obviously visible).

Cretaceous–Paleogene boundary

Geological signature, usually a thin band of rock containing much more iridium than other bands.

Geological signature, usually a thin band of rock containing much more iridium than other bands.

Badlands near Drumheller, Alberta, Canada, where glacial and post-glacial erosion have exposed the K–Pg boundary along with much other sedimentation (the exact boundary is a thin line not obviously visible).
Complex Cretaceous-Paleogene clay layer (gray) in the Geulhemmergroeve tunnels near Geulhem, the Netherlands. Finger is on the actual K–Pg boundary.

The K–Pg boundary marks the end of the Cretaceous Period, the last period of the Mesozoic Era, and marks the beginning of the Paleogene Period, the first period of the Cenozoic Era.

Discoscaphites iris ammonite from the Owl Creek Formation (Upper Cretaceous), Owl Creek, Ripley, Mississippi

Cretaceous–Paleogene extinction event

Sudden mass extinction of three-quarters of the plant and animal species on Earth, approximately 66 million years ago.

Sudden mass extinction of three-quarters of the plant and animal species on Earth, approximately 66 million years ago.

Discoscaphites iris ammonite from the Owl Creek Formation (Upper Cretaceous), Owl Creek, Ripley, Mississippi
Rudist bivalves from the Late Cretaceous of the Omani Mountains, United Arab Emirates. Scale bar is 10 mm.
Kronosaurus Hunt, a rendering by Dmitry Bogdanov in 2008. Large marine reptiles, including plesiosaurians such as these, became extinct at the end of the Cretaceous.
Tyrannosaurus was among the dinosaurs living on Earth before the extinction.
Hell Creek Formation
The K–Pg boundary exposure in Trinidad Lake State Park, in the Raton Basin of Colorado, shows an abrupt change from dark- to light-colored rock.
Radar topography reveals the 180 km-wide ring of the Chicxulub crater.
Artistic impression of the asteroid slamming into tropical, shallow seas of the sulfur-rich Yucatán Peninsula in what is today Southeast Mexico. The aftermath of this immense asteroid collision, which occurred approximately 66 million years ago, is believed to have caused the mass extinction of dinosaurs and many other species on Earth. The impact spewed hundreds of billions of tons of sulfur into the atmosphere, producing a worldwide blackout and freezing temperatures which persisted for at least a decade.
The river bed at the Moody Creek Mine, 7 Mile Creek / Waimatuku, Dunollie, New Zealand contains evidence of a devastating event on terrestrial plant communities at the Cretaceous–Paleogene boundary, confirming the severity and global nature of the event.
An artist's rendering of Thescelosaurus shortly after the K–Pg mass extinction. It survived by burrowing, but would soon die of starvation.

It marked the end of the Cretaceous Period, and with it the Mesozoic era, while heralding the beginning of the Cenozoic era, which continues to this day.

Flowering plant

Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae, commonly called angiosperms.

Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae, commonly called angiosperms.

Chamaenerion angustifolium, also known as fireweed or rosebay willowherb, is a flowering plant in the willowherb family Onagraceae.
Cross-section of a stem of the angiosperm flax:
1. pith, 2. protoxylem, 3. xylem, 4. phloem, 5. sclerenchyma (bast fibre), 6. cortex, 7. epidermis
A collection of flowers forming an inflorescence.
From 1736, an illustration of Linnaean classification
An auxanometer, a device for measuring increase or rate of growth in plants
Monocot (left) and dicot seedlings
Fluffy flowers of Tetradenia riparia (misty plume bush)
Flowers of Malus sylvestris (crab apple)
Flowers and leaves of Senecio angulatus (creeping groundsel)
Two bees on the composite flower head of creeping thistle, Cirsium arvense
Angiosperm life cycle
The fruit of Aesculus hippocastanum, the horse chestnut tree
A poster of twelve different species of flowers of the family Asteraceae
Lupinus pilosus
Bud of a pink rose

Over the course of the Cretaceous, angiosperms explosively diversified, becoming the dominant group of plants across the planet by the end of the period, corresponding with the decline and extinction of previously widespread gymnosperm groups.

Ammonoidea

Ammonoids are a group of extinct marine mollusc animals in the subclass Ammonoidea of the class Cephalopoda.

Ammonoids are a group of extinct marine mollusc animals in the subclass Ammonoidea of the class Cephalopoda.

Ammonite clean cut
Regions of the suture line and variants in suture patterns
An ammonite shell viewed in section, revealing the internal chambers and septa. Large polished examples are prized for both their aesthetic and scientific value.
An ammonitic ammonoid with the body chamber missing, showing the septal surface (especially at right) with its undulating lobes and saddles.
Iridescent ancient ammonite fossil on display at the American Museum of Natural History, New York City, around 2.5 feet in diameter
Asteroceras, a Jurassic ammonite from England
Fossil shell of ammonite Placenticeras whitfieldi showing punctures caused by the bite of a mosasaur, Peabody Museum of Natural History, Yale
Orthosphynctes, a Jurassic ammonite from Portugal
Jeletzkytes, a Cretaceous ammonite from South Dakota, US
A variety of ammonite forms, from Ernst Haeckel's 1904 Kunstformen der Natur (Art Forms of Nature)
Baculites ammonite from the Late Cretaceous of Wyoming, US: The original aragonite of the outer conch and inner septa has dissolved away, leaving this articulated internal mold.
Discoscaphites iris, Owl Creek Formation (Upper Cretaceous), Ripley, Mississippi, US
Heteromorph ammonite Didymoceras stevensoni
A drawing of an aptychus which was mistakenly described as a bivalve and given the name "Trigonellites latus", from the Kimmeridge Clay Formation in England
2 m Parapuzosia seppenradensis cast in Germany
Ammonoidea in Iran
A specimen of Hoploscaphites from the Pierre Shale of South Dakota, US: Much of the original shell, including the nacre, has survived.
An iridescent ammonite from Madagascar
Ammonites in the permanent collection of The Children's Museum of Indianapolis
Goniatites plebeiformis showing Goniatitic suture
Protrachyceras pseudoarchelonus showing Ceratitic suture
Lytoceras sutile showing Ammonitic suture

Ceratitic – lobes have subdivided tips, giving them a saw-toothed appearance and rounded, undivided saddles. This suture pattern is characteristic of Triassic ammonoids and appears again in the Cretaceous "pseudoceratites".

An artistic depiction of the major events in the history of Earth

Early Cretaceous

An artistic depiction of the major events in the history of Earth

The Early Cretaceous (geochronological name) or the Lower Cretaceous (chronostratigraphic name), is the earlier or lower of the two major divisions of the Cretaceous.

Late Cretaceous Map (Turonian)

Late Cretaceous

Late Cretaceous Map (Turonian)
Asteroids of only a few kilometers wide can release the energy of millions of nuclear weapons when colliding with planets (artist's impression).

The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale.

Rudists

Rudist bivalve, Maurens Formation, Upper Cretaceous, southwestern France
Comparison of the pteriomorph Volviceramus grandis (right) and the rudist Durania maxima (left)

Rudists are a group of extinct box-, tube- or ring-shaped marine heterodont bivalves belonging to the order Hippuritida that arose during the Late Jurassic and became so diverse during the Cretaceous that they were major reef-building organisms in the Tethys Ocean, until their complete extinction at the close of the Cretaceous.