The Jurassic period (/dʒʊəˈræsɪk/; from Jura Mountains) was a geologic period and system that spanned 56 million years from the end of the Triassic Period 201.3 million years ago (Mya) to the beginning of the Cretaceous Period 145 Mya.[note 1] The Jurassic constitutes the middle period of the Mesozoic Era, also known as the Age of Reptiles. The start of the period was marked by the major Triassic–Jurassic extinction event. Two other extinction events occurred during the period: the Pliensbachian-Toarcian extinction in the Early Jurassic, and the Tithonian event at the end; however, neither event ranks among the "Big Five" mass extinctions.
The Jurassic period is divided into three epochs: Early, Middle, and Late. Similarly, in stratigraphy, the Jurassic is divided into the Lower Jurassic, Middle Jurassic, and Upper Jurassic series of rock formations.
The Jurassic is named after the Jura Mountains within the European Alps, where limestone strata from the period were first identified. By the beginning of the Jurassic, the supercontinent Pangaea had begun rifting into two landmasses: Laurasia to the north, and Gondwana to the south. This created more coastlines and shifted the continental climate from dry to humid, and many of the arid deserts of the Triassic were replaced by lush rainforests.
On land, the fauna transitioned from the Triassic fauna, dominated by both dinosauromorph and crocodylomorph archosaurs, to one dominated by dinosaurs alone. The first birds also appeared during the Jurassic, having evolved from a branch of theropod dinosaurs. Other major events include the appearance of the earliest lizards, and the evolution of therian mammals, including primitive placentals. Crocodilians made the transition from a terrestrial to an aquatic mode of life. The oceans were inhabited by marine reptiles such as ichthyosaurs and plesiosaurs, while pterosaurs were the dominant flying vertebrates.
201.3–145 million years ago
|Mean atmospheric O
2 content over period duration
|c. 26 vol %|
(130 % of modern level)
|Mean atmospheric CO
2 content over period duration
|c. 1950 ppm|
(7 times pre-industrial level)
|Mean surface temperature over period duration||c. 16.5 °C|
(3 °C above modern level)
The chronostratigraphic term "Jurassic" is directly linked to the Jura Mountains, a mountain range mainly following the course of the France–Switzerland border. During a tour of the region in 1795, Alexander von Humboldt recognized the mainly limestone dominated mountain range of the Jura Mountains as a separate formation that had not been included in the established stratigraphic system defined by Abraham Gottlob Werner, and he named it "Jura-Kalkstein" ('Jura limestone') in 1799.
The Jurassic period is divided into three epochs: Early, Middle, and Late. Similarly, in stratigraphy, the Jurassic is divided into the Lower Jurassic, Middle Jurassic, and Upper Jurassic series of rock formations, also known as Lias, Dogger and Malm in Europe. The separation of the term Jurassic into three sections originated with Leopold von Buch. The faunal stages from youngest to oldest are:
|Tithonian||(152.1 ± 4 – 145 ± 4 Mya)|
|Kimmeridgian||(157.3 ± 4 – 152.1 ± 4 Mya)|
|Oxfordian||(163.5 ± 4 – 157.3 ± 4 Mya)|
|Callovian||(166.1 ± 4 – 163.5 ± 4 Mya)|
|Bathonian||(168.3 ± 3.5 – 166.1 ± 4 Mya)|
|Bajocian||(170.3 ± 3 – 168.3 ± 3.5 Mya)|
|Aalenian||(174.1 ± 2 – 170.3 ± 3 Mya)|
|Toarcian||(182.7 ± 1.5 – 174.1 ± 2 Mya)|
|Pliensbachian||(190.8 ± 1.5 – 182.7 ± 1.5 Mya)|
|Sinemurian||(199.3 ± 1 – 190.8 ± 1.5 Mya)|
|Hettangian||(201.3 ± 0.6 – 199.3 ± 1 Mya)|
During the early Jurassic period, the supercontinent Pangaea broke up into the northern supercontinent Laurasia and the southern supercontinent Gondwana; the Gulf of Mexico opened in the new rift between North America and what is now Mexico's Yucatan Peninsula. The Jurassic North Atlantic Ocean was relatively narrow, while the South Atlantic did not open until the following Cretaceous period, when Gondwana itself rifted apart. The Tethys Sea closed, and the Neotethys basin appeared. Climates were warm, with no evidence of a glacier having appeared. As in the Triassic, there was apparently no land over either pole, and no extensive ice caps existed.
The Jurassic geological record is good in western Europe, where extensive marine sequences indicate a time when much of that future landmass was submerged under shallow tropical seas; famous locales include the Jurassic Coast World Heritage Site in southern England and the renowned late Jurassic lagerstätten of Holzmaden and Solnhofen in Germany. In contrast, the North American Jurassic record is the poorest of the Mesozoic, with few outcrops at the surface. Though the epicontinental Sundance Sea left marine deposits in parts of the northern plains of the United States and Canada during the late Jurassic, most exposed sediments from this period are continental, such as the alluvial deposits of the Morrison Formation.
The Jurassic was a time of calcite sea geochemistry in which low-magnesium calcite was the primary inorganic marine precipitate of calcium carbonate. Carbonate hardgrounds were thus very common, along with calcitic ooids, calcitic cements, and invertebrate faunas with dominantly calcitic skeletons (Stanley and Hardie, 1998, 1999).
The first of several massive batholiths were emplaced in the northern American cordillera beginning in the mid-Jurassic, marking the Nevadan orogeny. Important Jurassic exposures are also found in Russia, India, South America, Japan, Australasia and the United Kingdom.
In Africa, Early Jurassic strata are distributed in a similar fashion to Late Triassic beds, with more common outcrops in the south and less common fossil beds which are predominated by tracks to the north. As the Jurassic proceeded, larger and more iconic groups of dinosaurs like sauropods and ornithopods proliferated in Africa. Middle Jurassic strata are neither well represented nor well studied in Africa. Late Jurassic strata are also poorly represented apart from the spectacular Tendaguru fauna in Tanzania. The Late Jurassic life of Tendaguru is very similar to that found in western North America's Morrison Formation.
During the Jurassic period, the primary vertebrates living in the sea were fish and marine reptiles. The latter include ichthyosaurs, which were at the peak of their diversity, plesiosaurs, pliosaurs, and marine crocodiles of the families Teleosauridae and Metriorhynchidae. Numerous turtles could be found in lakes and rivers.
In the invertebrate world, several new groups appeared, including rudists (a reef-forming variety of bivalves) and belemnites. Calcareous sabellids (Glomerula) appeared in the Early Jurassic. The Jurassic also had diverse encrusting and boring (sclerobiont) communities, and it saw a significant rise in the bioerosion of carbonate shells and hardgrounds. Especially common is the ichnogenus (trace fossil) Gastrochaenolites.
During the Jurassic period, about four or five of the twelve clades of planktonic organisms that exist in the fossil record either experienced a massive evolutionary radiation or appeared for the first time.
On land, various archosaurian reptiles remained dominant. The Jurassic was a golden age for the large herbivorous dinosaurs known as the sauropods—Camarasaurus, Apatosaurus, Diplodocus, Brachiosaurus, and many others—that roamed the land late in the period; their foraging grounds were either the prairies of ferns, palm-like cycads and bennettitales, or the higher coniferous growth, according to their adaptations. The smaller Ornithischian herbivore dinosaurs, like stegosaurs and small ornithopods were less predominant, but played important roles. They were preyed upon by large theropods, such as Ceratosaurus, Megalosaurus, Torvosaurus and Allosaurus. All these belong to the 'lizard hipped' or saurischian branch of the dinosaurs. During the Late Jurassic, the first avialans, like Archaeopteryx, evolved from small coelurosaurian dinosaurs. In the air, pterosaurs were common; they ruled the skies, filling many ecological roles now taken by birds, and may have already produced some of the largest flying animals of all time. Within the undergrowth were various types of early mammals, as well as tritylodonts, lizard-like sphenodonts, and early lissamphibians. The rest of the Lissamphibia evolved in this period, introducing the first salamanders and caecilians.
The arid, continental conditions characteristic of the Triassic steadily eased during the Jurassic period, especially at higher latitudes; the warm, humid climate allowed lush jungles to cover much of the landscape. Gymnosperms were relatively diverse during the Jurassic period. The Conifers in particular dominated the flora, as during the Triassic; they were the most diverse group and constituted the majority of large trees.
Extant conifer families that flourished during the Jurassic included the Araucariaceae, Cephalotaxaceae, Pinaceae, Podocarpaceae, Taxaceae and Taxodiaceae. The extinct Mesozoic conifer family Cheirolepidiaceae dominated low latitude vegetation, as did the shrubby Bennettitales. Cycads, similar to palm trees, were also common, as were ginkgos and Dicksoniaceous tree ferns in the forest. Smaller ferns were probably the dominant undergrowth. Caytoniaceous seed ferns were another group of important plants during this time and are thought to have been shrub to small-tree sized. Ginkgo plants were particularly common in the mid- to high northern latitudes. In the Southern Hemisphere, podocarps were especially successful, while Ginkgos and Czekanowskiales were rare.
Si logramos publicar esos nuevos resultados, sería el primer paso para cambiar formalmente la edad del Jurásico-Cretácico. A partir de ahí, la Unión Internacional de la Ciencias Geológicas y la Comisión Internacional de Estratigrafía certificaría o no, depende de los resultados, ese cambio.
Bryce Dallas Howard (born March 2, 1981) is an American actress and director. She is the eldest daughter of actor and director Ron Howard. She attended New York University's Tisch School of the Arts, but left before graduating to take on roles on Broadway. While starring as Rosalind in the play As You Like It, Howard caught the attention of director M. Night Shyamalan, and he cast her in what would be her breakout film, the psychological thriller The Village (2004). She then starred in Shyamalan's fantasy thriller Lady in the Water (2006). Her performance in Kenneth Branagh's 2006 film adaptation of As You Like It earned her a Golden Globe Award nomination. In 2006, she co-wrote and directed the short film Orchids. Howard also appeared as Gwen Stacy in Sam Raimi's superhero film Spider-Man 3 (2007).
Howard became more recognizable to audiences as the vampire Victoria in The Twilight Saga: Eclipse (2010). This project, as well as the action film Terminator Salvation (2009), were financially successful, but garnered mixed reviews from critics. In 2011, she had supporting roles in the films 50/50 and The Help. She gained further international recognition for playing Claire Dearing in the science fiction adventure films Jurassic World (2015) and Jurassic World: Fallen Kingdom (2018), the fourth and fifth installments in the Jurassic Park series, and her most financially successful films to date.Chris Pratt
Christopher Michael Pratt (born June 21, 1979) is an American actor. He rose to prominence for his television roles, particularly as Andy Dwyer in the NBC sitcom Parks and Recreation (2009–2015), for which he received critical acclaim and was nominated for the Critics' Choice Television Award for Best Supporting Actor in a Comedy Series in 2013. He also starred earlier in his career as Bright Abbott in The WB drama series Everwood (2002–2006) and has roles in Wanted (2008), Jennifer's Body (2009), Moneyball (2011), The Five-Year Engagement (2012), Zero Dark Thirty (2013), Delivery Man (2013), and Her (2013).
Pratt achieved leading man status in 2014 after starring in two critically and commercially successful films, Warner Animation Group's The Lego Movie as Emmet Brickowski and Marvel Studios' Guardians of the Galaxy as Star-Lord. In 2015, he starred in Jurassic World, the fourth installment in the Jurassic Park franchise, which was his most financially successful film up until the release of Avengers: Infinity War; he reprised the former role in the sequel Jurassic World: Fallen Kingdom in 2018. In 2015, Time named Pratt one of the 100 most influential people in the world on the annual Time 100 list.Pratt continued his leading man run in 2016 with The Magnificent Seven and Passengers. He reprises his role as Star-Lord in the Marvel Cinematic Universe in Guardians of the Galaxy Vol. 2 (2017), Avengers: Infinity War (2018) and its upcoming sequel, Avengers: Endgame (2019).Cladotheria
Cladotheria is a group (legion) of mammals that includes the ancestor of Dryolestoidea, Peramuridae and Zatheria (living therians plus all of its ancestors).Early Jurassic
The Early Jurassic epoch (in chronostratigraphy corresponding to the Lower Jurassic series) is the earliest of three epochs of the Jurassic period. The Early Jurassic starts immediately after the Triassic-Jurassic extinction event, 201.3 Ma (million years ago), and ends at the start of the Middle Jurassic 174.1 Ma.
Certain rocks of marine origin of this age in Europe are called "Lias" and that name was used for the period, as well, in 19th-century geology. In southern Germany rocks of this age are called Black Jurassic.Eutheria
Eutheria (; from Greek εὐ-, eu- "good" or "right" and θηρίον, thēríon "beast" hence "true beasts") is one of two mammalian clades with extant members that diverged in the Early Cretaceous or perhaps the Late Jurassic. Except for the North American Virginia opossum, which is a metatherian, all post-Miocene mammals indigenous to Europe, Africa, Asia, and North America north of Mexico are eutherians. Extant eutherians, their last common ancestor, and all extinct descendants of that ancestor are members of Placentalia.
Eutherians are distinguished from noneutherians by various phenotypic traits of the feet, ankles, jaws and teeth. All extant eutherians lack epipubic bones, which are present in all other living mammals (marsupials and monotremes). This allows for expansion of the abdomen during pregnancy.The oldest-known eutherian species is Juramaia sinensis, dated at 161 million years ago from the Jurassic in China.Eutheria was named in 1872 by Theodore Gill; in 1880 Thomas Henry Huxley defined it to encompass a more broadly defined group than Placentalia.Jeff Goldblum
Jeffrey Lynn Goldblum (; born October 22, 1952) is an American actor and musician. He has starred in some of the highest-grossing films of his era, Jurassic Park (1993) and Independence Day (1996), as well as their respective sequels, The Lost World: Jurassic Park (1997) and Jurassic World: Fallen Kingdom (2018), and Independence Day: Resurgence (2016).
Goldblum starred in films including Invasion of the Body Snatchers (1978), The Big Chill (1983), and Into the Night (1985) before coming to the attention of wider audiences in David Cronenberg's The Fly (1986) which earned him a Saturn Award for Best Actor.
His other films include The Adventures of Buckaroo Banzai Across the 8th Dimension (1984), The Tall Guy (1989), Deep Cover (1992), Powder (1995), The Prince of Egypt (1998), Cats & Dogs (2001), Igby Goes Down (2002), The Life Aquatic with Steve Zissou (2004), Adam Resurrected (2008), Le Week-End (2013), The Grand Budapest Hotel (2014), and Thor: Ragnarok (2017). He also starred in several TV series including the eighth and ninth seasons of Law & Order: Criminal Intent as Zack Nichols. For directing the short film Little Surprises, he was nominated for the Academy Award for Best Live Action Short Film.Jurassic Coast
The Jurassic Coast is a World Heritage Site on the English Channel coast of southern England. It stretches from Exmouth in East Devon to Studland Bay in Dorset, a distance of about 96 miles (154 km), and was inscribed on the World Heritage List in mid-December 2001.The site spans 185 million years of geological history, coastal erosion having exposed an almost continuous sequence of rock formation covering the Triassic, Jurassic and Cretaceous periods. At different times, this area has been desert, shallow tropical sea and marsh, and the fossilised remains of the various creatures that lived here have been preserved in the rocks.
Natural features seen on this stretch of coast include arches, pinnacles and stack rocks. In some places the sea has broken through resistant rocks to produce coves with restricted entrances, and in one place, the Isle of Portland is connected to the land by a narrow spit. In some parts of the coast, landslides are common. These have exposed a wide range of fossils, the different rock types each having its own typical fauna and flora, thus providing evidence of how animals and plants evolved in this region.
The area around Lulworth Cove contains a fossil forest, and 71 different rock strata have been identified at Lyme Regis, each with its own species of ammonite. The fossil collector Mary Anning lived here and her major discoveries of marine reptiles and other fossils were made at a time when the study of palaeontology was just starting to develop. The Charmouth Heritage Coast Centre provides information on the heritage coast, and the whole length of the site can be visited via the South West Coast Path.Jurassic Park
Jurassic Park is an American science fiction media franchise centered on a disastrous attempt to create a theme park of cloned dinosaurs. It began in 1990 when Universal Pictures and Amblin Entertainment bought the rights to the novel by Michael Crichton before it was even published.
The book was successful, as was Steven Spielberg's 1993 film adaptation, which led to four sequels, although only the first two films were based on the novels. Numerous video games based on the franchise have been created by various software developers since the release of the 1993 film. Since 1996, several water rides based on the series have been opened at various Universal theme parks.
The Jurassic Park Ultimate Trilogy was released on DVD and Blu-ray on October 25, 2011, in North America. The first film was re-released in 3D on April 5, 2013.The fourth film, Jurassic World, was initially scheduled to be released in the summer of 2005, but was delayed numerous times and was ultimately released in June 2015. It became the first film to gross over $500 million worldwide in its opening weekend, and grossed over $1.6 billion through the course of its theatrical run, making it the fifth highest-grossing film of all time. It was also the second highest-grossing film of 2015. When adjusted for monetary inflation, this film is the second highest grossing in the franchise after Jurassic Park. An animated film, Lego Jurassic World: The Indominus Escape, was released in October 2016 with the home media release of Jurassic World, alongside a short film, Employee Safety Video. Two other interactive Lego short films, Lego Jurassic World: Rescue Blue/Escape the Indoraptor, were also released in 2018, followed by an animated special, Lego Jurassic World: The Secret Exhibit, which aired on NBC later that year.
A fifth film, Jurassic World: Fallen Kingdom, was released in June 2018. The film grossed over $1.3 billion worldwide, making it the third Jurassic film to pass the billion dollar mark. It is the third highest-grossing film of 2018 and the 12th highest-grossing film of all time. A sixth film, tentatively titled Jurassic World 3, is scheduled to be released on June 11, 2021. As of 2000, the franchise had generated $5 billion in revenue, making it one of the highest-grossing media franchises of all time.In 2018, the first film was selected for preservation in the United States National Film Registry by the Library of Congress as being "culturally, historically, or aesthetically significant."Jurassic Park (film)
Jurassic Park is a 1993 American science fiction adventure film directed by Steven Spielberg and produced by Kathleen Kennedy and Gerald R. Molen. The first installment in the Jurassic Park franchise, it is based on the 1990 novel of the same name by Michael Crichton and a screenplay written by Crichton and David Koepp. The film is set on the fictional island of Isla Nublar, located off Central America's Pacific Coast near Costa Rica. There, billionaire philanthropist John Hammond and a small team of genetic scientists have created a wildlife park of de-extinct dinosaurs. When industrial sabotage leads to a catastrophic shutdown of the park's power facilities and security precautions, a small group of visitors and Hammond's grandchildren struggle to survive and escape the perilous island.
Before Crichton's novel was published, four studios put in bids for its film rights. With the backing of Universal Studios, Spielberg acquired the rights for $1.5 million before its publication in 1990; Crichton was hired for an additional $500,000 to adapt the novel for the screen. Koepp wrote the final draft, which left out much of the novel's exposition and violence and made numerous changes to the characters. Filming took place in California and Hawaii between August and November 1992, and post-production rolled until May 1993, supervised by Spielberg in Poland as he filmed Schindler's List.
The dinosaurs were created with groundbreaking computer-generated imagery by Industrial Light & Magic (ILM) and with life-sized animatronic dinosaurs built by Stan Winston's team. To showcase the film's sound design, which included a mixture of various animal noises for the dinosaur roars, Spielberg invested in the creation of DTS, a company specializing in digital surround sound formats. Following an extensive $65 million marketing campaign, which included licensing deals with 100 companies, Jurassic Park premiered on June 9, 1993, at the Uptown Theater in Washington, D.C., and was released on June 11 in the United States. It went on to gross over $914 million worldwide in its original theatrical run becoming the highest-grossing film of 1993 and the highest-grossing film ever at the time, a record held until the release of Titanic in 1997. It was well received by critics, who praised its special effects, John Williams' musical score, and Spielberg's direction. Following its 3D re-release in 2013 to celebrate its 20th anniversary, Jurassic Park became the seventeenth film in history to surpass $1 billion in ticket sales.
The film won more than twenty awards, including three Academy Awards for its technical achievements in visual effects and sound design. Jurassic Park is considered a landmark in the development of computer-generated imagery and animatronic visual effects and was followed by four commercially successful sequels, The Lost World: Jurassic Park (1997), Jurassic Park III (2001), Jurassic World (2015) and Jurassic World: Fallen Kingdom (2018), with a fifth sequel, currently titled Jurassic World 3, scheduled for a 2021 release.
In 2018, the film was selected for preservation in the United States National Film Registry by the Library of Congress as being "culturally, historically, or aesthetically significant".Jurassic Park III
Jurassic Park III is a 2001 American science fiction adventure film and the third installment in the Jurassic Park film series. The film stars Sam Neill, William H. Macy, Téa Leoni, Alessandro Nivola, Trevor Morgan, and Michael Jeter. It is the first film in the series Steven Spielberg did not direct; neither was it based on a book by Michael Crichton, although numerous scenes in the film were taken from Crichton's novels Jurassic Park and The Lost World. Events depicted in the film take place on Isla Sorna, an island off Central America's Pacific coast, where a divorced couple have tricked Dr. Alan Grant into helping them find their son.
After the success of Spielberg's film Jurassic Park, Joe Johnston expressed interest in directing a sequel. Spielberg gave Johnston permission to direct a third film in the series, if there was to be one. Production of Jurassic Park III began on August 30, 2000. Despite mixed reviews from critics, the film was successful at the box office, grossing $368 million worldwide. A sequel, Jurassic World, was released on June 12, 2015.Jurassic World
Jurassic World is a 2015 American science fiction adventure film, the fourth installment of the Jurassic Park film series, and the first film in a planned Jurassic World trilogy. It was directed by Colin Trevorrow, written by Derek Connolly and Trevorrow, produced by Frank Marshall and Patrick Crowley, and stars Chris Pratt, Bryce Dallas Howard, Vincent D'Onofrio, Ty Simpkins, Nick Robinson, Omar Sy, BD Wong, and Irrfan Khan.
Set 22 years after the events of Jurassic Park, Jurassic World takes place on the same fictional Central American island of Isla Nublar, which is located off the Pacific coast of Costa Rica, where a theme park of cloned dinosaurs has operated for nearly a decade. The park plunges into chaos when a genetically-engineered dinosaur escapes from its enclosure and goes on a rampage.
Universal Pictures intended to begin production of a fourth Jurassic Park film in 2004 for a mid-2005 release but development stalled while the script underwent several revisions. Following a suggestion from Spielberg, writers Rick Jaffa and Amanda Silver explored the idea of a functional dinosaur park. Once Trevorrow was hired as director in 2013, he followed the same idea while developing a new script with Derek Connolly. Filming lasted from April to August 2014 in Louisiana and at the original Jurassic Park locations in Hawaii. The dinosaurs were created by Industrial Light & Magic using CGI and by Legacy Effects using life-sized animatronics.
Production was completed on May 10, 2015, and Jurassic World was released in over 60 countries beginning on June 10, 2015. After a record-breaking opening weekend during which it became the first film to gross over $500 million, Jurassic World generated $1.6 billion in box office revenue, ranking fifth among the highest-grossing films of all time. It was also the second-highest-grossing film of 2015 and the highest-grossing in the franchise. Furthermore, it is the highest grossing film ever released by Universal Pictures unadjusted for inflation. A sequel titled Jurassic World: Fallen Kingdom was released in June 2018.Late Jurassic
The Late Jurassic is the third epoch of the Jurassic period, and it spans the geologic time from 163.5 ± 1.0 to 145.0 ± 0.8 million years ago (Ma), which is preserved in Upper Jurassic strata.In European lithostratigraphy, the name "Malm" indicates rocks of Late Jurassic age. In the past, Malm was also used to indicate the unit of geological time, but this usage is now discouraged to make a clear distinction between lithostratigraphic and geochronologic/chronostratigraphic units.List of Jurassic Park characters
The following is a list of fictional characters from Michael Crichton's novel Jurassic Park, its sequel The Lost World, and their film adaptations, Jurassic Park and The Lost World: Jurassic Park. Also included are characters from the films Jurassic Park III, Jurassic World, and Jurassic World: Fallen Kingdom, which are not adaptations and have no original source novels but contain characters and events based on the fictional universe of Crichton's novels.Mesozoic
The Mesozoic Era ( or ) is an interval of geological time from about 252 to 66 million years ago. It is also called the Age of Reptiles and the Age of Conifers.The Mesozoic ("middle life") is one of three geologic eras of the Phanerozoic Eon, preceded by the Paleozoic ("ancient life") and succeeded by the Cenozoic ("new life"). The era is subdivided into three major periods: the Triassic, Jurassic, and Cretaceous, which are further subdivided into a number of epochs and stages.
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. The Mesozoic was a time of significant tectonic, climate 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. Birds first appeared in the Jurassic (however, true toothless birds appeared first in the Cretaceous), having evolved from a branch of theropod dinosaurs. The first mammals also appeared during the Mesozoic, but would remain small—less than 15 kg (33 lb)—until the Cenozoic. The flowering plants (angiosperms) arose in the Triassic or Jurassic and came to prominence in the late Cretaceous when they replaced the conifers and other gymnosperms as the dominant trees.Middle Jurassic
The Middle Jurassic is the second epoch of the Jurassic Period. It lasted from about 174 to 163 million years ago.
Fossil-bearing rocks from the Middle Jurassic are relatively rare, but some important formations include the Forest Marble Formation in England, the Kilmaluag Formation in Scotland, the Daohugou Beds in China, Itat Formation in Russia, and the Isalo III Formation of western Madagascar.Morrison Formation
The Morrison Formation is a distinctive sequence of Upper Jurassic sedimentary rock found in the western United States which has been the most fertile source of dinosaur fossils in North America. It is composed of mudstone, sandstone, siltstone, and limestone and is light gray, greenish gray, or red. Most of the fossils occur in the green siltstone beds and lower sandstones, relics of the rivers and floodplains of the Jurassic period.
It is centered in Wyoming and Colorado, with outcrops in Montana, North Dakota, South Dakota, Nebraska, Kansas, the panhandles of Oklahoma and Texas, New Mexico, Arizona, Utah, and Idaho. Equivalent rocks under different names are found in Canada. It covers an area of 1.5 million square kilometers (600,000 square miles), although only a tiny fraction is exposed and accessible to geologists and paleontologists. Over 75% is still buried under the prairie to the east, and much of its western paleogeographic extent was eroded during exhumation of the Rocky Mountains.
It was named after Morrison, Colorado, where the first fossils in the formation were discovered by Arthur Lakes in 1877. That same year, it became the center of the Bone Wars, a fossil-collecting rivalry between early paleontologists Othniel Charles Marsh and Edward Drinker Cope. In Colorado, New Mexico, and Utah, the Morrison Formation was a major source of uranium ore.Theria
Theria (; Greek: θηρίον theríon, wild beast) is a subclass of mammals amongst the Theriiformes (the sister taxon to Yinotheria). Theria includes the eutherians (including the placental mammals) and the metatherians (including the marsupials).
(541.0 Mya–2.5 Gya)
|Archean eon (2.5–4 Gya)|
|Hadean eon (4–4.6 Gya)|