70-708: The Hensel Formation or Hensel Sand is a Mesozoic geologic formation in Texas . Fossil ornithopod tracks have been reported from the formation. A stratigraphic column at the Mount Bonnell Fault location reveals the following sequence: the Lower Cretaceous Trinity Group is overlain by the Edwards Group . This is followed by Upper Cretaceous formations , starting with the Del Rio Clay , then
140-505: A divaricate branching habit, similar to that of Banksia . It has been suggested that Williamsoniaceae are a paraphyletic (not containing all descendants of a common ancestor) assemblage of all Bennettitales that do not belong to the Cycadeoidaceae. In general, bennettitalean leaves are attached to the stem with a helical (corkscrew) arrangement. Some leaves (most species of Nilssoniopteris , etc.) are narrow, solitary blades with
210-504: A monophyletic group when paired with Gnetales. a study in 2006 suggested that Bennettitales, Angiosperms, and Gigantopteridales form a clade based on the presence of oleanane . Molecular evidence has consistently contradicted the Anthophyte hypothesis, finding that Angiosperms are the sister group to all living gymnosperms, including Gnetales. Some authors have suggested due to similarities between their seed coats, Bennettitales form
280-427: A palmate appearance similar to early species of Ginkgo . The foliage of bennettitaleans resembles that of cycads to such an extent that the foliage of the two groups cannot be reliably distinguished based on gross morphology alone. However, fossil foliage which preserves the cuticle can be assigned to either group with confidence. The stomata of bennettitaleans are described as syndetocheilic . This means that
350-476: A boom of dinosaurian evolution on land as the continents began to separate from each other (Nyasasaurus from 243 to 210 million years ago, approximately 235–30 ma, some of them separated into Sauropodomorphs, Theropods and Herrerasaurids), as well as the first pterosaurs . During the Late Triassic, some advanced cynodonts gave rise to the first Mammaliaformes . All this climatic change, however, resulted in
420-630: A clade with the gymnosperm orders of Gnetales and Erdtmanithecales , dubbed the "BEG group". However, this proposal has been contested by other authors, who contend that these similarities are only superficial and do not indicate a close relationship. A 2017 phylogeny based on molecular signatures of fossilised cuticles found that Bennettitales were more closely related to the Ginkgo +Cycads clade than conifers, and were closely related to Nilssonia and Ptilozamites . The oldest confirmed fossils of bennettitaleans are leaves of Nilssoniopteris shanxiensis ,
490-582: A coating. This contrasts with the earth's current flora, in which the dominant land plants in terms of number of species are angiosperms . The earliest members of the genus Ginkgo first appeared during the Middle Jurassic. This genus is represented today by a single species, Ginkgo biloba . Modern conifer groups began to radiate during the Jurassic. Bennettitales , an extinct group of gymnosperms with foliage superficially resembling that of cycads gained
560-585: A decline in diversity of sauropods, stegosaurs, and other high-browsing groups, with sauropods particularly scarce in North America. Some island-hopping dinosaurs, such as Eustreptospondylus , evolved to cope with the coastal shallows and small islands of ancient Europe. Other dinosaurs rose up to fill the empty space that the Jurassic-Cretaceous extinction left behind, such as Carcharodontosaurus and Spinosaurus . Seasons came back into effect and
630-477: A few million years before the Triassic–Jurassic extinction event. Sea levels began to rise during the Jurassic, probably caused by an increase in seafloor spreading . The formation of new crust beneath the surface displaced ocean waters by as much as 200 m (656 ft) above today's sea level, flooding coastal areas. Furthermore, Pangaea began to rift into smaller divisions, creating new shoreline around
700-477: A global distribution during the Late Triassic, and represented one of the most common groups of Mesozoic seed plants. Flowering plants radiated during the early Cretaceous, first in the tropics , but the even temperature gradient allowed them to spread toward the poles throughout the period. By the end of the Cretaceous, angiosperms dominated tree floras in many areas, although some evidence suggests that biomass
770-659: A large die-out known as the Triassic–Jurassic extinction event, in which many archosaurs (excluding pterosaurs, dinosaurs and crocodylomorphs ), most synapsids , and almost all large amphibians became extinct, as well as 34% of marine life, in the Earth's fourth mass extinction event. The cause is debatable; flood basalt eruptions at the Central Atlantic magmatic province is cited as one possible cause. The Jurassic ranges from 200 million years to 145 million years ago and features three major epochs: The Early Jurassic,
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#1733086212694840-407: A long proboscis , and it has been suggested that they fed on nectar produced by bennettitalean reproductive structures, such as the bisexual williamsoniacean reproductive structure Williamsoniella , which had a long, narrow central receptacle which was likely otherwise inaccessible. Early Cretaceous bennettitalean pollen has been found directly associated with a proboscis bearing fly belonging to
910-429: A smooth-edged ("entire") margin. Most leaf morphotypes ( Pterophyllum , Ptilophyllum , Zamites , Otozamites , etc.) are pinnate (feather-shaped), with many small leaf segments attached to a central shaft. Others ( Anomozamites , a few species of Nilssoniopteris ) are incompletely pinnate (sawtooth-shaped) and transitional between these two end members. One unusual leaf form, Eoginkgoites , even approaches
980-596: A species from the upper part of the Upper Shihhotse Formation in Shanxi Province , China . This strata is dated to the early Kungurian stage of the early Permian ( Cisuralian ), around 281 million years ago. Supposed Carboniferous-Permian records of Pterophyllum do not have conclusive bennettitalean affinities or have been reinterpreted as cycad foliage in the form genus Pseudoctenis . True Permian records of benettitalean leaves are rare; outside of
1050-435: A variety of niches, beginning in the mid-Triassic 4 million to 6 million years after the extinction, and not fully proliferated until 30 million years after the extinction. Animal life was then dominated by various archosaurs: dinosaurs , pterosaurs, and aquatic reptiles such as ichthyosaurs, plesiosaurs, and mosasaurs . The climatic changes of the late Jurassic and Cretaceous favored further adaptive radiation. The Jurassic
1120-472: Is a stub . You can help Misplaced Pages by expanding it . Mesozoic The Mesozoic Era is the era of Earth's geological history , lasting from about 252 to 66 million years ago , comprising the Triassic , Jurassic and Cretaceous Periods . It is characterized by the dominance of gymnosperms such as cycads , ginkgoaceae and araucarian conifers, and of archosaurian reptiles such as
1190-460: Is associated with the female reproductive structure Williamsonia , though it is uncertain whether the parent plants were monoecious (male and female reproductive structures being present on the same plant) or dioecious (where each plant has only one gender of reproductive organ). Weltrichia was likely primarily wind-pollinated , with some species possibly pollinated by beetles. Several groups of Jurassic and Early Cretaceous insects possessed
1260-440: Is dense and thick, with many layers of differentiated cells. This contrasts with the thin, biseriate (two cell-layer) integument of gnetophytes. Bennettitaleans also lack another gnetophyte-like trait: a sheath of fused bracteoles enveloping the seed. Most integument cells are not unusual in size or shape. However, near the micropyle the innermost layer of integument cells become radially-oriented and elongated, partially closing in on
1330-664: Is often enclosed in paired synangia (pollen sacs). The synangia lie on the adaxial (inner) edge of pollen-bearing leaf-like structures known as microsporophylls . This contrasts with cycads, all of which lack discrete synangia and bear pollen on the abaxial (outer) surface of their microsporophylls. Many bennettitaleans are bisporangiate , where the pollen and ovules are hosted on the same (bisexual or hermaphrodite) cone. Cavities filled with curved synangia-bearing microsporophylls are encased by thin radiating structures, including thick, infertile interseminal scales and fertile sporophylls with ovules at their tips. The presence of ovules at
1400-468: Is set by the Permian–Triassic extinction event , during which it has been estimated that up to 90-96% of marine species became extinct although those approximations have been brought into question with some paleontologists estimating the actual numbers as low as 81%. It is also known as the "Great Dying" because it is considered the largest mass extinction in the Earth's history. The upper boundary of
1470-522: Is thought that a large meteor smashed into earth 66 million years ago, creating the Chicxulub Crater in an event known as the K-Pg Extinction (formerly K-T), the fifth and most recent mass extinction event, in which 75% of life became extinct, including all non-avian dinosaurs. Compared to the vigorous convergent plate mountain-building of the late Paleozoic, Mesozoic tectonic deformation
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#17330862126941540-765: The Buda Limestone , and finally the Eagle Ford Group . The Trinity Group consists of the Hammett Formation , Cow Creek Formation, Hensel Formation, and Lower and Upper Glen Rose Formation . The Hammett and the lower portion of the Upper Glen Rose act as confining units (or aquitard ) for the Middle Trinity Aquifer . This article about a specific stratigraphic formation in the United States
1610-749: The Indian subcontinent , which collided with the Asian plate during the Cenozoic, giving rise to the Himalayas . The Triassic was generally dry, a trend that began in the late Carboniferous , and highly seasonal, especially in the interior of Pangaea. Low sea levels may have also exacerbated temperature extremes. With its high specific heat capacity , water acts as a temperature-stabilizing heat reservoir, and land areas near large bodies of water—especially oceans—experience less variation in temperature. Because much of Pangaea's land
1680-483: The Isle of Portland , England, which Buckland gave the genus name Cycadeoidea . Buckland provided a description of the family and two species, but failed to give a description of the genus, which has led to Buckland's description of the family being considered invalid by modern taxonomic standards. In publications in 1870, Scottish botanist William Carruthers and English paleobotanist William Crawford Williamson described
1750-491: The Maastrichtian , assignable to Pterophyllum. A possible late record has been reported from the early Oligocene of eastern Australia and Tasmania , assignable to the genus Ptilophyllum , but no cuticle was preserved, making the referral inconclusive. Bennettitales is typically considered the sole order in the class Bennettitopsida Engler (1897) or Cycadeoideopsida Scott (1923) . Most paleobotanists prefer
1820-541: The Middle Triassic , and williamsoniaceans became globally distributed by the end of the period. The oldest bennettitalean reproductive structures are small Williamsonia "flowers" from the Middle Triassic Esk Formation of Australia . While Williamsoniaceae had a global distribution, Cycadeoidaceae appear to have been primarily confined to the western parts of Laurasia , and are primarily known from
1890-554: The Permian Period allowed for the radiation of many new lifeforms. In particular, the extinction of the large herbivorous pareiasaurs and carnivorous gorgonopsians left those ecological niches empty. Some were filled by the surviving cynodonts and dicynodonts , the latter of which subsequently became extinct. Recent research indicates that it took much longer for the reestablishment of complex ecosystems with high biodiversity, complex food webs, and specialized animals in
1960-702: The Permian period and became extinct in most areas toward the end of the Cretaceous . Bennettitales were amongst the most common seed plants of the Mesozoic , and had morphologies including shrub and cycad -like forms. The foliage of bennettitaleans is superficially nearly indistinguishable from that of cycads, but they are distinguished from cycads by their more complex flower-like reproductive organs, at least some of which were likely pollinated by insects . Although certainly gymnosperms sensu lato (cone-bearing seed plants),
2030-655: The dinosaurs ; a hot greenhouse climate; and the tectonic break-up of Pangaea . The Mesozoic is the middle of the 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 mass extinction in Earth's history, and ended with the Cretaceous–Paleogene extinction event , another mass extinction whose victims included
2100-411: The non-avian dinosaurs , pterosaurs , mosasaurs , and plesiosaurs . The Mesozoic was a time of significant tectonic, climatic, and evolutionary activity. The supercontinent Pangaea began to break apart into separate landmasses. 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
2170-453: The Atlantic seaway, which has grown continually larger until today. The further separation of the continents gave opportunity for the diversification of new dinosaurs. The Cretaceous is the longest period of the Mesozoic, but has only two epochs: Early and Late Cretaceous. The Early Cretaceous spans from 145 to 100 million years ago. The Early Cretaceous saw the expansion of seaways and
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2240-580: The Cretaceous. Bennettitales were widespread and abundant during the Jurassic and Early Cretaceous, however Bennettitales severely declined during the Late Cretaceous, coincident with the rise of flowering plants , being mostly extinct by the end of the period, with the final known remains from the Northern Hemisphere being found in the polar latitude Kakanaut Formation in Chukotka , Russia, dating to
2310-400: The Late Cretaceous declined for poorly understood reasons, though this might be due to tendencies of the fossil record, as their diversity seems to be much higher than previously thought. Birds became increasingly common and diversified into a variety of enantiornithe and ornithurine forms. Though mostly small, marine hesperornithes became relatively large and flightless, adapted to life in
2380-532: The Mesozoic is set at the Cretaceous–Paleogene extinction event (or K–Pg extinction event ), which may have been caused by an asteroid impactor that created Chicxulub Crater on the Yucatán Peninsula . Towards the Late Cretaceous, large volcanic eruptions are also believed to have contributed to the Cretaceous–Paleogene extinction event. Approximately 50% of all genera became extinct, including all of
2450-642: The Mesozoic, but would remain small—less than 15 kg (33 lb)—until the Cenozoic. Flowering plants appeared in the Early Cretaceous and would rapidly diversify through the end of the era, replacing conifers and other gymnosperms ( sensu lato ), such as ginkgoales , cycads and bennettitales as the dominant group of plants. The phrase "Age of Reptiles" was introduced by the 19th century paleontologist Gideon Mantell who viewed it as dominated by diapsids such as Iguanodon , Megalosaurus , Plesiosaurus , and Pterodactylus . The current name
2520-468: 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
2590-549: The Middle Jurassic, and the Late Jurassic. The Early Jurassic spans from 200 to 175 million years ago. The climate was tropical and much more humid than the Triassic, as a result of the large seas appearing between the land masses. In the oceans, plesiosaurs , ichthyosaurs and ammonites were abundant. On land, dinosaurs and other archosaurs staked their claim as the dominant race, with theropods such as Dilophosaurus at
2660-715: The Shihhotse Formation they are only found in the Late Permian (likely Changhsingian )-age Umm Irna Formation in Jordan . This formation is notable for the early occurrence of other Mesozoic-style flora, including the earliest records of corystospermalean foliage ( Dicroidium ). The order Fredlindiales (containing the genus Fredlindia ) from the Late Triassic of Gondwana appears to be closely related to Bennettitales, but differs from it in some aspects of its reproductive organs. The bennettitalean fossil record reappeared in
2730-468: The Tethys Ocean. Temperatures continued to increase, then began to stabilize. Humidity also increased with the proximity of water, and deserts retreated. The climate of the Cretaceous is less certain and more widely disputed. Probably, higher levels of carbon dioxide in the atmosphere are thought to have almost eliminated the north–south temperature gradient : temperatures were about the same across
2800-510: The beginnings of the breakup of Pangaea and the opening of the Tethys Ocean . Ecosystems had recovered from the Permian extinction. Algae, sponge, corals, and crustaceans all had recovered, and new aquatic reptiles evolved, such as ichthyosaurs and nothosaurs . On land, pine forests flourished, as did groups of insects such as mosquitoes and fruit flies. Reptiles began to get bigger and bigger, and
2870-431: The current level (about 21%) throughout the Mesozoic, some concluding they were lower in the Triassic and part of the Jurassic but higher in the Cretaceous, and some concluding they were higher throughout most or all of the Triassic, Jurassic and Cretaceous. The dominant land plant species of the time were gymnosperms , which are vascular, cone-bearing, non-flowering plants such as conifers that produce seeds without
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2940-439: The dawn of the Mesozoic, ocean plankton communities transitioned from ones dominated by green archaeplastidans to ones dominated by endosymbiotic algae with red-algal-derived plastids. This transition is speculated to have been caused by an increasing paucity of many trace metals in the Mesozoic ocean. Bennettitales Bennettitales (also known as cycadeoids ) is an extinct order of seed plants that first appeared in
3010-600: The dramatic rifting of the supercontinent Pangaea, which gradually split into a northern continent, Laurasia , and a southern continent, Gondwana . This created the passive continental margin that characterizes most of the Atlantic coastline (such as along the U.S. East Coast ) today. By the end of the era, the continents had rifted into nearly their present forms, though not their present positions. Laurasia became North America and Eurasia , while Gondwana split into South America , Africa , Australia , Antarctica and
3080-455: The extinct family Zhangsolvidae , providing evidence that this family acted as pollinators for the group. The interseminal scales of Bennettitales ovulate cones may have become fleshy at maturity, which could have potentially made then attractive to wild animals that served as seed dispersers. The Cycadeoideaceae (originally "Cycadeoideae") were named by English geologist William Buckland in 1828, from fossil trunks found in Jurassic strata on
3150-467: The fern prairies, chased by many new predators such as Allosaurus . Conifer forests made up a large portion of the forests. In the oceans, plesiosaurs were quite common, and ichthyosaurs flourished. This epoch was the peak of the reptiles. The Late Jurassic spans from 163 to 145 million years ago. During this epoch, the first avialans , such as Archaeopteryx , evolved from small coelurosaurian dinosaurs. The increase in sea levels opened up
3220-460: The first crocodilians and dinosaurs evolved, which sparked competition with the large amphibians that had previously ruled the freshwater world, respectively mammal-like reptiles on land. Following the bloom of the Middle Triassic, the Late Triassic, from 237 to 201 million years ago, featured frequent heat spells and moderate precipitation (10–20 inches per year). The recent warming led to
3290-519: The first known reproductive organs of the Bennettitales from Jurassic strata of Yorkshire and Jurassic-Cretaceous strata of the Isle of Wight and the Isle of Portland. Caruthers was the first to recognise that Bennettitales had distinct differences from cycads, and established the tribes "Williamsonieae" and "Bennettiteae", with the latter being named after the genus Bennettites named by Caruthers in
3360-478: The food web. In the oceans, mosasaurs ruled, filling the role of the ichthyosaurs, which, after declining, had disappeared in the Cenomanian-Turonian boundary event . Though pliosaurs had gone extinct in the same event, long-necked plesiosaurs such as Elasmosaurus continued to thrive. Flowering plants, possibly appearing as far back as the Triassic, became truly dominant for the first time. Pterosaurs in
3430-446: The form of cones , which produce pollen and ovules (unfertilized seeds). The cones have a thick central receptacle surrounded by simple, helically-arranged fertile and infertile structures. Tissue at the base of the cone forms layers of scale-like or petal-like bracts to protect the radiating inner structures. Some authors refer to bennettitalean cones as "flowers", though they are not equivalent to true angiosperm flowers. Pollen
3500-486: The fossil record. The Late Cretaceous spans from 100 to 66 million years ago. The Late Cretaceous featured a cooling trend that would continue in the Cenozoic Era. Eventually, tropics were restricted to the equator and areas beyond the tropic lines experienced extreme seasonal changes in weather. Dinosaurs still thrived, as new taxa such as Tyrannosaurus , Ankylosaurus , Triceratops and hadrosaurs dominated
3570-477: The main paired guard cells develop from the same mother cells as the subsidiary cells which surround them. This contrasts with the haplocheilic stomata of cycads and conifers. In haplocheilic stomata, the ring of subsidiary cells are not derived from the same original structures as the guard cells. This fundamental difference is the main way to differentiate bennettitalean and cycad foliage. Like other gymnosperms, bennettitalean reproductive inflorescences come in
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#17330862126943640-453: The micropyle. The nucellus and integument are unfused above the chalaza (base of the seed), unlike cycads or gnetophytes, where the layers are fused for much of their height. Cycadeoidaceans have been suggested to have been self-pollinating, with their stems and cones buried underground, although it has alternatively been proposed that they were pollinated by beetles. The flower-like williamsoniacean male reproductive structure Weltrichia
3710-599: The non- avian dinosaurs. The Triassic ranges roughly from 252 million to 201 million years ago, preceding the Jurassic Period. The period is bracketed between the Permian–Triassic extinction event and the Triassic–Jurassic extinction event , two of the " big five ", and it is divided into three major epochs: Early, Middle, and Late Triassic. The Early Triassic, about 252 to 247 million years ago,
3780-455: The open sea. Metatherians and primitive eutherian also became common and even produced large and specialised genera such as Didelphodon and Schowalteria . Still, the dominant mammals were multituberculates, cimolodonts in the north and gondwanatheres in the south. At the end of the Cretaceous, the Deccan traps and other volcanic eruptions were poisoning the atmosphere. As this continued, it
3850-415: The other hand, feature an exposed crown of tapering microsporophylls with adaxial rows of synangia. The microsporophylls may host a single linear row of paired synangia, or instead synangia arranged in a pinnate (feather-shaped) pattern. Seeds are dicotyledonous (possess two embryonic leaves ), with a central embryo surrounded by three layers: the thin megagametophyte, the slightly thicker nucellus , and
3920-437: The planet, and about 10° C higher than today. The circulation of oxygen to the deep ocean may also have been disrupted, preventing the decomposition of large volumes of organic matter, which was eventually deposited as " black shale ". Different studies have come to different conclusions about the amount of oxygen in the atmosphere during different parts of the Mesozoic, with some concluding oxygen levels were lower than
3990-641: The poles got seasonally colder, but some dinosaurs still inhabited the polar forests year round, such as Leaellynasaura and Muttaburrasaurus . The poles were too cold for crocodiles, and became the last stronghold for large amphibians such as Koolasuchus . Pterosaurs got larger as genera such as Tapejara and Ornithocheirus evolved. Mammals continued to expand their range: eutriconodonts produced fairly large, wolverine -like predators such as Repenomamus and Gobiconodon , early therians began to expand into metatherians and eutherians , and cimolodont multituberculates went on to become common in
4060-458: The protective integument . The upper tip of the seed is tapered and opens through a thin and often extended micropyle . A long, narrow micropyle extending out of the seed is superficially similar to the condition in living gnetophytes . Once the seed is fertilized, the micropyle is sealed by a plug-shaped extension of the nucellus. Unlike living gymnosperms, the tip of the nucellus lacks a pollen chamber (receptacle for stored pollen). The integument
4130-1027: The relationships of bennettitaleans to other seed plants is debated. Their general resemblance to cycads is contradicted by numerous more subtle features of their reproductive systems and leaf structure. Some authors have linked bennettitaleans to angiosperms (flowering plants) and gnetophytes (a rare and unusual group of modern gymnosperms), forming a broader group known as Anthophyta . Molecular data contradicts this, with gnetophytes found to be much more genetically similar to conifers . The exact position of Bennettitales remains uncertain. Bennettitales are divided into two families, Cycadeoidaceae and Williamsoniaceae , which have distinct growth habits . Cycadeoidaceae had stout, cycad -like trunks with bisporangiate (containing both megaspores and microspores ) strobili (cones) serving as their reproductive structures. Williamsoniaceae either had bisporangiate or monosporangiate cones, and distinctly slender and branching woody trunks. The Williamsoniaceae grew as woody shrubs with
4200-543: The same publication , the name being in honour of British botanist John Joseph Bennett . The order Bennettitales was erected by German botanist Adolf Engler in 1892, who recognised the group as separate from the Cycadales. The Anthophyte hypothesis erected by Arber and Parking in 1907 posited that angiosperms arose from Bennettitales, as suggested by the wood-like structures and rudimentary flowers . Based on morphological data, however, Bennettitales were classified as
4270-644: The tips of sporophylls, rather than the tips of stems, is a major difference between the cones of bennettitaleans and gnetophytes. As the cone is fertilized and matures, the microsporophylls wither away and the ovules transform into seeds. Most bennettitaleans in the family Williamsoniaceae are instead monosporangiate , with separate pollen and ovule-producing (unisexual) cones on the same plant. The ovule-producing (female) cones ( Williamsonia , etc . ) are similar to mature bisporangiate cones, with interseminal scales and ovule-tipped sporophylls enclosed by bracts. Pollen-producing (male) cones ( Weltrichia , etc . ), on
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#17330862126944340-497: The top of the food chain. The first true crocodiles evolved, pushing the large amphibians to near extinction. All-in-all, archosaurs rose to rule the world. Meanwhile, the first true mammals evolved, remaining relatively small, but spreading widely; the Jurassic Castorocauda , for example, had adaptations for swimming, digging and catching fish. Fruitafossor , from the late Jurassic Period about 150 million years ago,
4410-531: Was about the size of a chipmunk, and its teeth, forelimbs and back suggest that it dug open the nests of social insects (probably termites , as ants had not yet appeared) ; Volaticotherium was able to glide for short distances, such as modern flying squirrels . The first multituberculates such as Rugosodon evolved. The Middle Jurassic spans from 175 to 163 million years ago. During this epoch, dinosaurs flourished as huge herds of sauropods, such as Brachiosaurus and Diplodocus , filled
4480-877: Was comparatively mild. The sole major Mesozoic orogeny occurred in what is now the Arctic , creating the Innuitian orogeny , the Brooks Range , the Verkhoyansk and Cherskiy Ranges in Siberia, and the Khingan Mountains in Manchuria. This orogeny was related to the opening of the Arctic Ocean and suturing of the North China and Siberian cratons to Asia. In contrast, the era featured
4550-523: Was distant from its shores, temperatures fluctuated greatly, and the interior probably included expansive deserts . Abundant red beds and evaporites such as halite support these conclusions, but some evidence suggests the generally dry climate of the Triassic was punctuated by episodes of increased rainfall. The most important humid episodes were the Carnian Pluvial Event and one in the Rhaetian ,
4620-533: Was dominated by deserts in the interior of the Pangaea supercontinent. The Earth had just witnessed a massive die-off in which 95% of all life became extinct, and the most common vertebrate life on land were Lystrosaurus , labyrinthodonts , and Euparkeria along with many other creatures that managed to survive the Permian extinction. Temnospondyls reached peak diversity during the early Triassic. The Middle Triassic, from 247 to 237 million years ago, featured
4690-505: Was originally described as the "secondary" era, following the "primary" ( Paleozoic ), and preceding the Tertiary . Following the Paleozoic, the Mesozoic extended roughly 186 million years, from 251.902 to 66 million years ago when the Cenozoic Era began. This time frame is separated into three geologic periods . From oldest to youngest: The lower boundary of the Mesozoic
4760-577: Was proposed in 1840 by the British geologist John Phillips (1800–1874). "Mesozoic" literally means 'middle life', deriving from the Greek prefix meso- ( μεσο- 'between') and zōon ( ζῷον 'animal, living being'). In this way, the Mesozoic is comparable to the Cenozoic ( lit. ' new life ' ) and Paleozoic ('old life') eras as well as the Proterozoic ('earlier life') Eon. The Mesozoic Era
4830-516: Was still dominated by cycads and ferns until after the Cretaceous–Paleogene extinction. Some plant species had distributions that were markedly different from succeeding periods; for example, the Schizeales , a fern order, were skewed to the Northern Hemisphere in the Mesozoic, but are now better represented in the Southern Hemisphere. The extinction of nearly all animal species at the end of
4900-485: Was the height of archosaur diversity, and the first birds and eutherian mammals also appeared. Some have argued that insects diversified in symbiosis with angiosperms, because insect anatomy , especially the mouth parts, seems particularly well-suited for flowering plants. However, all major insect mouth parts preceded angiosperms, and insect diversification actually slowed when they arrived, so their anatomy originally must have been suited for some other purpose. At
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