Portal:Mesozoic

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Introduction

The Mesozoic Portal

Diplodocus longus(2).jpg

The Mesozoic Era ( /ˌmɛz.əˈz.ɪk, ˌmɛz.-, ˌmɛs-, ˌm.zə-, -z-, ˌm.sə-, -s-/ mez-ə-ZOH-ik, mez-oh-, mess-, mee-zə-, -⁠zoh-, mee-sə-, -⁠soh-), also called the Age of Reptiles and the Age of Conifers, is the second-to-last era of Earth's geological history, lasting from about 252 to 66 million years ago and comprising the Triassic, Jurassic and Cretaceous Periods. It is characterized by the dominance of archosaurian reptiles, like the dinosaurs; an abundance of conifers and ferns; a hot greenhouse climate; and the tectonic break-up of Pangaea. The Mesozoic is the middle of three eras since complex life evolved: the Paleozoic, the Mesozoic, and the Cenozoic.

The era began in the wake of the Permian–Triassic extinction event, the largest well-documented mass extinction in Earth's history, and ended with the Cretaceous–Paleogene extinction event, another mass extinction whose victims included the non-avian dinosaurs, pterosaurs, mosasaurs, and plesiosaurs. The Mesozoic was a time of significant tectonic, climatic, and evolutionary activity. The era witnessed the gradual rifting of the supercontinent Pangaea into separate landmasses that would move into their current positions during the next era. The climate of the Mesozoic was varied, alternating between warming and cooling periods. Overall, however, the Earth was hotter than it is today. Dinosaurs first appeared in the Mid-Triassic, and became the dominant terrestrial vertebrates in the Late Triassic or Early Jurassic, occupying this position for about 150 or 135 million years until their demise at the end of the Cretaceous. Archaic birds appeared in the Jurassic, having evolved from a branch of theropod dinosaurs, then true toothless birds appeared in the Cretaceous. The first mammals also appeared during the Mesozoic, but would remain small—less than 15 kg (33 lb)—until the Cenozoic. The flowering plants appeared in the early Cretaceous Period and would rapidly diversify throughout the end of the era, replacing conifers and other gymnosperms as the dominant group of plants. (Full article...)

Selected article on the Mesozoic world and its legacies

Skeletal mount of Deinonychus.
Deinonychus is a genus of carnivorous dromaeosaurid coelurosaurian dinosaurs. There is one described species, Deinonychus antirrhopus. This species, which could grow up to 3.4 metres (11 ft) long, lived during the early Cretaceous Period, about 115–108 million years ago (from the mid-Aptian to early Albian stages). Fossils have been recovered from the U.S. states of Montana, Wyoming, and Oklahoma, in rocks of the Cloverly Formation and Antlers Formation, though teeth that may belong to Deinonychus have been found much farther east in Maryland.

Paleontologist John Ostrom's study of Deinonychus in the late 1960s revolutionized the way scientists thought about dinosaurs, leading to the "dinosaur renaissance" and igniting the debate on whether dinosaurs were warm-blooded or cold blooded. Before this, the popular conception of dinosaurs had been one of plodding, reptilian giants. Ostrom noted the small body, sleek, horizontal posture, ratite-like spine, and especially the enlarged raptorial claws on the feet, which suggested an active, agile predator. The etymology "terrible claw" refers to the unusually large, sickle-shaped talon on the second toe of each hind foot. The fossil YPM 5205 preserves a large, strongly curved ungual. Ostrom looked at crocodile and bird claws and reconstructed the claw for YPM 5205 as over 150 millimetres (5.9 in) long.

In both the Cloverly and Antlers formations, Deinonychus remains have been found closely associated with those of the ornithopod Tenontosaurus. Teeth discovered associated with Tenontosaurus specimens imply they were hunted, or at least scavenged upon, by Deinonychus. (see more...)

Selected article on the Mesozoic in human science, culture and economics

Oil shale.
Oil shale geology is a branch of geologic sciences which studies the formation and composition of oil shales–fine-grained sedimentary rocks containing significant amounts of kerogen, and belonging to the group of sapropel fuels. Oil shale formation takes place in a number of depositional settings and has considerable compositional variation. Oil shales can be classified by their composition (carbonate minerals such as calcite or detrital minerals such as quartz and clays) or by their depositional environment (large lakes, shallow marine, and lagoon/small lake settings). Much of the organic matter in oil shale is of algal origin, but may also include remains of vascular land plants. Three major type of organic matter (macerals) in oil shale are telalginite, lamalginite, and bituminite. Some oil-shale deposits also contain metals which include vanadium, zinc, copper, uranium.

Most oil shale deposits were formed during Middle Cambrian, Early and Middle Ordovician, Late Devonian, Late Jurassic, and Paleogene times through burial by sedimentary loading on top of the algal swamp deposits, resulting in conversion of the organic matter to kerogen by diagenetic processes. The largest deposits are found in the remains of large lakes such as the deposits of the Green River Formation of Wyoming and Utah, USA. Oil-shale deposits formed in the shallow seas of continental shelves generally are much thinner than large lake basin deposits. (see more...)

Selected image

Fossil of the Middle Jurassic ammonoid Leioceras opalinum

A fossil shell of the graphoceratid ammonoid Leioceras opalinum. The shell dates back to the Aalenian age (170.3–174.1 million years ago) of the Middle Jurassic epoch and is about 38 mm in diameter. It was collected between Ohmenhausen and Reutlingen, Germany.
Photo credit: H. Zell

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Close up of Tryannosaurus "Sue" Skull at the Field Museum of Natural History in Chicago, IL.

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Topics

Geochronology - Triassic (Early - Middle - Late) - Jurassic (Early - Middle - Late) - Cretaceous (Early - Late)

Mesozoic landmasses - Pangaea - Gondwana - Laurasia - Africa - North America - South America - Antarctica - Asia - Australia - Europe - Appalachia - Laramidia

Major Mesozoic events - Mesozoic Marine Revolution - Carnian Pluvial Event - Triassic-Jurassic extinction event - Toarcian turnover - Cretaceous Terrestrial Revolution - Western Interior Seaway anoxia - Chicxulub impact - Cretaceous-Paleogene extinction event

Triassic biota appearances - Belemnites - Crickets - Dinosaurs - Earwigs - Ichthyosauromorphs - Pseudosuchians - Pterosaurs - Sauropterygians - Testudinates

Jurassic biota appearances - Ammonitids - Ankylosaurs - Avialans - Caecilians - Carnosaurs - Caudates - Ceratopsians - Ceratosaurs - Coelurosaurs - Cryptodires - Dromaeosaurids - Equisetum - Frogs - Horse-flies - Lepidopterans - Lizards - Mammals - Ornithopods - Pterodactyloids - Sauropods - Snakeflies - Stegosaurs - Tyrannosauroids

Cretaceous biota appearances - Abalones - Anglerfishes - Ants - Bees - Catfishes - Copepods - Cormorants - Crocodilians - Flowering plants - Fowls - Geckos - Hadrosauroids - Hermit crabs - Lobsters - Mosasaurs - Ornithomimosaurs - Oviraptorosaurs - Pachycephalosaurs - Requiem sharks - Sea turtles - Snakes - Squids - Stingrays - Therizinosaurs

Fossil sites - Berlin–Ichthyosaur State Park - Petrified Forest National Park - Dinosaur National Monument - Dinosaur Valley State Park

Stratigraphic units - Chinle Formation - Elliot Formation - Ischigualasto Formation - Kimmeridge Clay - Morrison Formation - Oxford Clay Formation - Solnhofen lithographic limestone - Tendaguru Formation - Crato Formation - Dinosaur Park Formation - Djadochta Formation - Hell Creek Formation - Niobrara Formation - Two Medicine Formation - Wessex Formation - Yixian Formation

History - History of paleontology - Timeline of paleontology - Timeline of ankylosaur research - Timeline of ceratopsian research - Timeline of ceratosaur research - Timeline of dromaeosaurid research - Timeline of hadrosaur research - Timeline of ichthyosaur research - Timeline of plesiosaur research - Timeline of stegosaur research - Timeline of tyrannosaur research

Researchers - William Buckland - Edward Drinker Cope - Jack Horner - Othniel Charles Marsh - Gideon Algernon Mantell - John Ostrom - Sir Richard Owen - Harry Govier Seeley - Samuel Wendell Williston

Culture - Treatise on Invertebrate Paleontology - Vertebrate Paleontology - Walking with Dinosaurs - Jurassic Park

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