The end of the cretaceous period

The results of this study, which were based on estimated real global biodiversity, showed that between 628 and 1,078 non-avian dinosaur species were alive at the end of the Cretaceous and underwent sudden extinction after the Cretaceous–Paleogene extinction event.

Nov 14, 2018 · This particular species, dubbed Mirarce eatoni, is about 75 million years old, meaning it dates from the end of the Cretaceous period. It is described in a new paper published in the journal PeerJ. The Cretaceous ended with perhaps the most famous mass-extinction event of all, but there were other extinctions of note during the period. There were two minor mass-extinctions during the middle Cretaceous. The later of the two, at around 94 million years ago, is notable for the extinction of the ichthyosaurs.Cretaceous Period - Mesozoic, Paleogene, Cenozoic: The rocks that were either deposited or formed during the Cretaceous Period make up the Cretaceous System. The Cretaceous System is divided into two rock series, Lower and Upper, which correspond to units of time known as the Early Cretaceous Epoch (145 million to 100.5 million years …Dinosaurs went extinct about 65 million years ago (at the end of the Cretaceous Period), …Dinosaur - Extinction Causes, Evidence, & Theory: The mass extinction of dinosaurs 66 million years ago remains a misconception; the fossil record shows that dinosaurs were already in decline during the late Cretaceous. Proposed causes for the extinction of dinosaurs have included everything from disease, heat waves, cold spells, faunal changes, and an asteroid collision during the K–T boundary.At the end of the Cretaceous period a mass extinction event occurred when a large _____ struck Earth and caused the extinction of all _____ (except birds), flying reptiles, and ammonites. asteroid, dinosaurs৩০ জুল, ২০১৯ ... Donald Trump was there at the end of the Cretaceous period when illegal aliens caused the dinosaurs to become extinct. But he's not calling ...Embark on a journey through the Cretaceous Period, exploring its unique inhabitants, the emergence of flowering plants, and the shifting continents that shaped the world. This comprehensive guide delves into the captivating history, diverse ecosystems, and the cataclysmic event that ended the Age of Reptiles.

Introduction. The Cretaceous Period was the last of three geologic time periods in the Mesozoic Era. The Cretaceous began approximately 145 million years ago at the end of the Jurassic Period and ended about 66 million years ago. The Cretaceous was succeeded by the Paleogene Period of the Cenozoic Era. The Cretaceous is perhaps best known for ... Dinosaur - Extinction Causes, Evidence, & Theory: The mass extinction of dinosaurs 66 million years ago remains a misconception; the fossil record shows that dinosaurs were already in decline during the late Cretaceous. Proposed causes for the extinction of dinosaurs have included everything from disease, heat waves, cold spells, faunal changes, and an asteroid collision during the K–T boundary. Mesozoic. Mesozoic (252-66 million years ago) means 'middle life' and this is the time of the dinosaurs. This era includes the Triassic, Jurassic, and Cretaceous Periods, names that may be familiar to you. It ended with a massive meteorite impact that caused a mass extinction, wiping out the dinosaurs and up to 80% of life on Earth.Dakota Formation sandstones, the remains of beach sands and sediments dumped by rivers draining into the Cretaceous seas, formed in central Kansas during this period. Igneous kimberlite pipes erupted toward the surface in eastern Kansas. Mass extinction occurred at the end of this period. Jurassic Period (201 million years ago to 145 million ...... the end of the Cretaceous, the following three tectonic element can be distinguished along the Arabian Plate margin (Fig.4): 1) An elevated zone ...Alvarez's main evidence is an abundance of iridium in the KT boundary, a thin stratum dividing Cretaceous rocks from rocks of the Tertiary period. Iridium ...৬ দিন আগে ... The Cretaceous–Paleogene extinction event is normally attributed to a catastrophic asteroid impact combined with intense volcanic activity. This ...Cretaceous Period - Dinosaurs, Plants, Marine Life: Although the fossil record is irregular in quality and quantity for the Early Cretaceous, it is obvious that dinosaurs continued their lengthy dominance of the land. The Late Cretaceous record is much more complete, particularly in the case of North America and Asia. It is known, for instance, that during the Late Cretaceous many dinosaur ...

The impact of a miles-wide asteroid and the end of the Cretaceous period were catastrophic to life on Earth, erasing more than 70 percent of the planet's species, according to the most recent ...Dinosaurs went extinct about 65 million years ago (at the end of the Cretaceous Period), …Part 3: Cretaceous Period This video is the last in a series about the dinosaur story. Learn about the Cretaceous Period. By the end of this period, 66 million years ago, dinosaurs will be extinct. _ The Telling the Dinosaur Story series explores the fascinating time of dinosaurs as told through various National Natural Landmarks (NNLs) …Sep 26, 2022 · The Cretaceous period happened from 145.5 to 65.5 million years ago. This was when more coastlines appeared. Seasons also became more evident as the planet’s climate became cooler. Magnolias, oaks, and hickories started to thrive in the north by the Cretaceous period’s end. By the end of this period, a huge asteroid hit the planet. Apr 27, 2023 · The initial epoch of the Paleogene Period and the Cenozoic Era is the Paleocene Epoch, which marks the first subdivision of geologic time after the extinction of the dinosaurs and the end of the Cretaceous Period. In western North America, the uplift of the Rocky Mountains, which started in the Cretaceous, continued throughout the Paleocene. Phylogenies of several plant lineages suggest that the Cretaceous–Paleogene (K/Pg) event marking the end of the Cretaceous played a role in shaping modern tropical lowland rainforests (13–15), but the fate of tropical forests following the K/Pg boundary is not well understood.Assessing plant extinction and recovery requires a thoroughly sampled …

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Its fossil record is representative of a time at the end of the Cretaceous that lasted from 145 million to 66 million years ago, just before the asteroid hit—about 10 million years younger than ...It is known as the Cretaceous Period or simply Cretaceous, the period of the geological time scale that culminates the Mesozoic Era (which began 252.2 million years ago and ended 66 million years ago). It is the third after the Triassic (initial period) and Jurassic (intermediate period) periods. The Cretaceous began 145 million years ago and ...Extinct Species Whether or not the asteroid or comet that carved the Chicxulub crater caused the extinction of more than half the planet's species at the end of the Cretaceous remains a matter...March 11, 2022 3:21 p.m. PT. 2 min read. This ancient softshell turtle survived the dinosaur-ending extinction event at the end of the Cretaceous period. Sergey Krasovskiy. Scientists have ...Phylogenies of several plant lineages suggest that the Cretaceous–Paleogene (K/Pg) event marking the end of the Cretaceous played a role in shaping modern tropical lowland rainforests (13–15), but the fate of tropical forests following the K/Pg boundary is not well understood.Assessing plant extinction and recovery requires a thoroughly sampled …The Jurassic ( / dʒʊˈræsɪk / juu-RASS-ik [2]) is a geologic period and stratigraphic system that spanned from the end of the Triassic Period 201.4 million years ago (Mya) to the beginning of the Cretaceous Period, approximately 145 Mya. The Jurassic constitutes the middle period of the Mesozoic Era and is named after the Jura Mountains ...

Hudson Seaway – Major seaway of North America during the Cretaceous Period; Lake Agassiz – Large lake in central North America at the end of the last glacial period; Sundance Sea – Inland sea that existed in North America during the mid-to-late Jurassic Period of the Mesozoic Era; Zuñi sequence – A Jurassic-Cretaceous cratonic sequenceMost people are familiar with the extinction at the end of the Cretaceous period (end of the Mesozoic era) that ended the reign of the dinosaurs. How does ...Apr 27, 2023 · During the Cretaceous Period the first flowering plants appeared and rapidly diversified. Also, the Rocky Mountains began to rise from the Cretaceous Interior Seaway. However, the event that has caught the public’s imagination is the mass extinction that marks the end of one era with dinosaurs and begins another without them. Cretaceous Period - Dinosaurs, Plants, Marine Life: Although the fossil record is irregular in quality and quantity for the Early Cretaceous, it is obvious that dinosaurs continued their lengthy dominance of the land. The Late Cretaceous record is much more complete, particularly in the case of North America and Asia. It is known, for instance, that during …The hybodonts became extinct towards the end of the Late Cretaceous period, some 66 million years ago. The first fossilised Hybodus teeth were found in the UK around the mid-19th century, ...Telling the Dinosaur Story: Part 3 Cretaceous Period. Part 3: Cretaceous Period This video is the last in a series about the dinosaur story. Learn about the Cretaceous Period. By the end of this period, 66 million years ago, dinosaurs will be extinct.There were two significant extinction events in the Permian Period. The smaller, at the end of a time interval called the Capitanian, occurred about 260 million years ago. The event at the end of the Permian Period (at the end of a time interval called the Changshanian) was much larger and may have eliminated more than three-quarters of species ...Apr 27, 2023 · During the Cretaceous Period the first flowering plants appeared and rapidly diversified. Also, the Rocky Mountains began to rise from the Cretaceous Interior Seaway. However, the event that has caught the public’s imagination is the mass extinction that marks the end of one era with dinosaurs and begins another without them. There were two significant extinction events in the Permian Period. The smaller, at the end of a time interval called the Capitanian, occurred about 260 million years ago. The event at the end of the Permian Period (at the end of a time interval called the Changshanian) was much larger and may have eliminated more than three-quarters of species ...Dinosaurs appeared during the Late Triassic period [ca. 225 million years ago (Mya)] and diversified rapidly, becoming the dominant terrestrial vertebrates of Jurassic and Cretaceous ecosystems (ca. 206–65 Mya) [1–3]. Dinosauria was a successful clade by any standard: it was species rich (with >650 Mesozoic taxa currently considered valid ... Tyrannosaurus rex arose during the Cretaceous period about 85 million years ago, and thrived as a top land predator until the dinosaurs went extinct 20 million years later. This skeleton, on ...

Mesozoic. Mesozoic (252-66 million years ago) means 'middle life' and this is the time of the dinosaurs. This era includes the Triassic, Jurassic, and Cretaceous Periods, names that may be familiar to you. It ended with a massive meteorite impact that caused a mass extinction, wiping out the dinosaurs and up to 80% of life on Earth.

৭ অক্টো, ২০১৮ ... Illustration of the K/T Event at the end of the Cretaceous Period. A ten-kilometre-wide asteroid/comet is entering the Earth's atmosphere and a ...They prevailed for more than 160 million years before vanishing along with the nonbird dinosaurs at the end of the Cretaceous period, around 66 million years ago.Dinosaurs went extinct about 65 million years ago (at the end of the Cretaceous Period), after living on Earth for about 165 million years. If all of Earth time from the very beginning of the dinosaurs to today were compressed into 365 days (one calendar year), the dinosaurs appeared January 1 and became extinct the third week of September. The Cretaceous Period 144 to 65 Million Years Ago. The Cretaceous is usually noted …From a distance, most Cretaceous birds would have looked similar to modern birds. If you could hold one, though, you’d be in for a surprise: many Cretaceous birds had teeth and wing claws. Many of the Cretaceous birds went extinct at the end of the period. In the oceans, the dolphin-like ichthyosaurs, which had evolved back in the Early ...The end boundary for the Mesozoic era, the Cretaceous-Paleogene boundary, is defined by a 20-inch (50 centimeters) thick sliver of rock in El Kef, Tunisia, which contains well-preserved fossils ...Asteroid headed towards Earth at the end of the Cretaceous. Depiction by Mary Parrish, Smithsonian. Introduction National Middle School Science Standards. Earth Science, Life Science. Key Terms. paleontology, dinosaur, fossil record, mass extinction, asteroid, Cretaceous period, K-T boundary ...The Cretaceous-Paleogene boundary ~65.5 million years ago marks one of the three largest mass extinctions in the past 500 million years. ... the rule of dinosaurs came to an abrupt end ∼65 million years ago, when all nonavian dinosaurs and flying reptiles disappeared. ... was deposited in the extremely brief period between the arrival …Dinosaurs appeared during the Late Triassic period [ca. 225 million years ago (Mya)] and diversified rapidly, becoming the dominant terrestrial vertebrates of Jurassic and Cretaceous ecosystems (ca. 206–65 Mya) [1–3]. Dinosauria was a successful clade by any standard: it was species rich (with >650 Mesozoic taxa currently considered valid ...

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Extinctions at the End of the Cretaceous. Paragraph 1：It has long been recognized that the dinosaurs disappeared from the fossil record at the end of the Cretaceous period (65 million years ago), and as more knowledge has been gained, we have learned that many other organisms disappeared at about the same time. The …Extinct Species Whether or not the asteroid or comet that carved the Chicxulub crater caused the extinction of more than half the planet's species at the end of the Cretaceous remains a matter...The end of the Cretaceous Period saw one of the most dramatic mass extinctions Earth has ever seen. Find out what brought about the end of the dinosaurs and many other animals too. The fossil record shows that for the first 175 million years of their existence, dinosaurs took on a huge variety ... The extinction occurred at the end of the Cretaceous Period, about 65.5 million years ago. Who became extinct? In addition to the non-avian dinosaurs, vertebrates that were lost at the end of the Cretaceous include the flying pterosaurs, and the mosasaurs, plesiosaurs and ichthyosaurs of the oceans.The history of life has been punctuated by several mass extinctions. For example, the impact of a meteorite may have wiped out most of the dinosaurs and many forms of marine life at the end of the Cretaceous period. Fossils indicate that plants were less severely affected by this mass extinction.Dinosaur - Extinction Causes, Evidence, & Theory: The mass extinction of dinosaurs 66 million years ago remains a misconception; the fossil record shows that dinosaurs were already in decline during the late Cretaceous. Proposed causes for the extinction of dinosaurs have included everything from disease, heat waves, cold spells, faunal changes, and an asteroid collision during the K–T boundary. The Cretaceous is a geologic period and system that spans 79 million years from the end of the Jurassic Period 145 million years ago (Mya) to the beginning of the Paleogene Period 66 Mya. It is the last period of the Mesozoic Era. The Cretaceous Period is usually abbreviated K, for its German translation Kreide (chalk).But if confirmed, the second meteorite strike in quick succession could have delivered a one-two punch in the global catastrophe at the end of the Cretaceous period, according to the study.1991. The Mesozoic Era [3] is the second-to-last 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 archosaurian reptiles, such as the dinosaurs; an abundance of gymnosperms, (such as ginkgoales, bennettitales) and ...The history of life has been punctuated by several mass extinctions. For example, the impact of a meteorite may have wiped out most of the dinosaurs and many forms of marine life at the end of the Cretaceous period. Fossils indicate that plants were less severely affected by this mass extinction.২৫ আগ, ২০১৭ ... The end-Cretaceous extinction is the most well-known, since it wiped out the dinosaurs (minus the birds, of course) and opened the door for ... ….

Telling the Dinosaur Story: Part 3 Cretaceous Period. Part 3: Cretaceous Period This video is the last in a series about the dinosaur story. Learn about the Cretaceous Period. By the end of this period, 66 million years ago, dinosaurs will be extinct.At the end of the Cretaceous period a mass extinction event occurred when a large _____ struck Earth and caused the extinction of all _____ (except birds), flying reptiles, and ammonites. asteroid, dinosaursIts fossil record is representative of a time at the end of the Cretaceous that lasted from 145 million to 66 million years ago, just before the asteroid hit—about 10 million years younger than ...The end of the Cretaceous is defined by the abrupt Cretaceous-Paleogene boundary (K-Pg boundary), a geologic signature associated with the mass extinction that lies between the Mesozoic and Cenozoic Eras . Etymology and history1991. The Mesozoic Era [3] is the second-to-last 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 archosaurian reptiles, such as the dinosaurs; an abundance of gymnosperms, (such as ginkgoales, bennettitales) and ... Nov 17, 2011 · By Morgan Kelly on Nov. 17, 2011, 9 a.m. A cosmic one-two punch of colossal volcanic eruptions and meteorite strikes likely caused the mass-extinction event at the end of the Cretaceous period that is famous for killing the dinosaurs 65 million years ago, according to two Princeton University reports that reject the prevailing theory that the ... Death came quickly at the end of the Cretaceous. Taking a census of the damage is difficult, partially, Robertson says, because dinosaurs get a disproportionate amount of attention.Scientists estimate about 90% of the plant and animal species on Earth during the Permian Period were extinct by the end of the period. Marine animals living in reefs and shallow waters were especially hard hit, ... As with the end-Cretaceous mass extinction, the cause of the end-Permian extinction is difficult to determine. The possibilities ...১৫ ডিসে, ২০০৫ ... Abstract One of the greatest mass extinctions in Earth's history occurred at the end of the Cretaceous era, sixty-five million years (Myr) ... The end of the cretaceous period, Scientists call it the Permian-Triassic extinction or "the Great Dying" -- not to be confused with the better-known Cretaceous-Tertiary extinction that signaled the end of the dinosaurs 65 million years ago. Whatever happened during the Permian-Triassic period was much worse: No class of life was spared from the devastation., Carnotaurus was a sauropod of spectacular proportions. Learn more about the Carnotaurus, Early Cretaceous dinosaurs, and dinosaurs of all eras. Advertisement CARNOTAURUS (CAR-noh-TORE-us) Period: Early Cretaceous Advertisement Order, Subord..., At the end of the Cretaceous period 66 million years ago, a giant asteroid impact at Chicxulub off the coast of Mexico led to darkened skies and global cooling, killing off all the dinosaurs save ..., The End of the Dinosaurs: The K-T extinction. Almost all the large vertebrates on Earth, on land, at sea, and in the air (all dinosaurs, plesiosaurs, mosasaurs, and pterosaurs) suddenly became extinct about 65 Ma, at the end of the Cretaceous Period. At the same time, most plankton and many tropical invertebrates, especially reef-dwellers ..., At the end of the Cretaceous period a mass extinction event occurred when a large _____ struck Earth and caused the extinction of all _____ (except birds), flying reptiles, and ammonites. asteroid, dinosaurs , The End of the Dinosaurs: The K-T extinction. Almost all the large vertebrates on Earth, on land, at sea, and in the air (all dinosaurs, plesiosaurs, mosasaurs, and pterosaurs) suddenly became extinct about 65 Ma, at the end of the Cretaceous Period. At the same time, most plankton and many tropical invertebrates, especially reef-dwellers ... , Type of Dinosaur: Titanosaur, Sauropod. Existed: Late Cretaceous, 97-93.5 Mya. Where found: South America. Estimated length: 30-39.7 m (98-130 ft.) Argentinosaurus was a titanosaur that lived in South America in the Late Cretaceous. It grew to almost 40 m (131 ft.) in length and 7.3 m (24 ft.) in shoulder height., Paragragh 1: It has long been recognized that the dinosaurs disappeared from the fossil record at the end of the Cretaceous period (65 million years ago), and as more knowledge has been gained, we have learned that many other organisms disappeared at about the same time. The microscopic plankton (free-floating plants and animals) with ..., When it comes to Cretaceous dinosaurs, we often think of Triceratops and T. rex, though these dinosaurs only lived at the end of the period, around 68-66 million years ago. 'The Cretaceous is 80 million years long, so there's a lot of turnover in that time,' says Susie. , Oct 18, 2023 · It began 145 million years ago and ended 66 million years ago and featured the extinction of the dinosaurs at the end of the period. , Ankylosaurus is a genus of armored dinosaur.Its fossils have been found in geological formations dating to the very end of the Cretaceous Period, about 68–66 million years ago, in western North America, making it among the last of the non-avian dinosaurs.It was named by Barnum Brown in 1908; it is monotypic, containing only A. magniventris.The generic …, Mass extinction at the end of the Cretaceous Period (66 million years ago) Best known for killing off the dinosaurs, the end- Cretaceous mass extinction also caused many other casualties. Ammonoids ( marine mollusks ), pterosaurs (gliding reptiles), mosasaurs (swimming reptiles), and a host of other plants and animals died out completely or ... , The results of this study, which were based on estimated real global biodiversity, showed that between 628 and 1,078 non-avian dinosaur species were alive at the end of the Cretaceous and underwent sudden extinction after the Cretaceous–Paleogene extinction event., Mass extinction at the end of the Cretaceous Period (66 million years ago) Best known for killing off the dinosaurs, the end- Cretaceous mass extinction also caused many other casualties. Ammonoids ( marine mollusks ), pterosaurs (gliding reptiles), mosasaurs (swimming reptiles), and a host of other plants and animals died out completely or ..., By Morgan Kelly on Nov. 17, 2011, 9 a.m. A cosmic one-two punch of colossal volcanic eruptions and meteorite strikes likely caused the mass-extinction event at the end of the Cretaceous period that is famous for killing the dinosaurs 65 million years ago, according to two Princeton University reports that reject the prevailing theory that …, Discovered in Egypt, the creature is one of the few dinosaur fossils found so far in Africa that dates to the late Cretaceous period, roughly 80 to 66 million years ago. ... By the end of the ..., Embark on a journey through the Cretaceous Period, exploring its unique inhabitants, the emergence of flowering plants, and the shifting continents that shaped the world. This comprehensive guide delves into the captivating history, diverse ecosystems, and the cataclysmic event that ended the Age of Reptiles., It began 145 million years ago and ended 66 million years ago and featured the extinction of the dinosaurs at the end of the period., Devonian Period — 359 million years ago; Ordovician Period — 443 million years ago; The mass extinctions at the end of the Cretaceous Period is the most familiar because it brought about the demise of the dinosaurs. However, the most dramatic one, in terms of number of species lost, occurred at the end of the Permian Period. , ১৫ এপ্রি, ২০১৪ ... The end of the Cretaceous is defined by the K–Pg boundary, a geologic signature associated with the mass extinction which lies between the ..., Jan 29, 2018 · At the end of the Cretaceous Period, and the end of the Mesozoic Era came another mass extinction. This extinction is generally called the K-T Extinction. The "K" comes from the German abbreviation for Cretaceous, and the "T" is from the next period on the Geologic Time Scale - the Tertiary Period of the Cenozoic Era. , Oct 9, 2023 · K–T extinction, abbreviation of Cretaceous–Tertiary extinction, also called K–Pg extinction or Cretaceous–Paleogene extinction, a global mass extinction event responsible for eliminating approximately 80 percent of all species of animals at or very close to the boundary between the Cretaceous and Paleogene periods, about 66 million years ago. , At the end of the Cretaceous, the geological record shows that these seaways retreated from the continents back into the major ocean basins. No one knows why.Over a period of about 100,000 years, while the seas pulled back, climates around the world became dramatically more extreme: warmer days, cooler nights; hotter summers, colder winters., The Deccan Traps, in present-day west-central India (), formed from a series of short (∼100-ky) intermittent eruption pulses (), with two main phases (8, 9) at ∼67.4 Ma (toward the end of the Cretaceous) and ∼66.1 Ma (starting just before the boundary and continuing through the earliest Paleogene) erupting an estimated >10 6 km 3 of magma over a duration of ∼710,000 y (9, 10)., Jul 27, 2021 · The history of life has been punctuated by several mass extinctions. For example, the impact of a meteorite may have wiped out most of the dinosaurs and many forms of marine life at the end of the Cretaceous period. Fossils indicate that plants were less severely affected by this mass extinction. , During Early Cretaceous time, carbonates continued to be deposited on the passive margin of eastern North America. Before the end of Early Cretaceous time, siliciclastic sediments began to be deposited, as part of a clastic wedge consisting of sands and muds from the Appalachian region laid down in nonmarine and shallow marine settings. , When it comes to Cretaceous dinosaurs, we often think of Triceratops and T. rex, though these dinosaurs only lived at the end of the period, around 68-66 million years ago. 'The Cretaceous is 80 million years long, so there's a lot of turnover in that time,' says Susie. , British researchers studying the fossil record of extinctions at the end of. the Cretaceous period—when the dinosaurs and many other species. disappeared—now suggest that most died out ..., Extinct Species Whether or not the asteroid or comet that carved the Chicxulub crater caused the extinction of more than half the planet's species at the end of the Cretaceous remains a matter..., The extinction occurred at the end of the Cretaceous Period, about 65.5 million years ago. Who became extinct? In addition to the non-avian dinosaurs, vertebrates that were lost at the end of the Cretaceous include the flying pterosaurs, and the mosasaurs, plesiosaurs and ichthyosaurs of the oceans., Learn about the mass extinction event 66 million years ago and the evidence for what ended the age of the dinosaurs. ... At that point, as the Cretaceous period yielded to the Paleogene, it seems ..., ... the end of the Cretaceous, the following three tectonic element can be distinguished along the Arabian Plate margin (Fig.4): 1) An elevated zone ..., March 11, 2022 3:21 p.m. PT. 2 min read. This ancient softshell turtle survived the dinosaur-ending extinction event at the end of the Cretaceous period. Sergey Krasovskiy. Scientists have ...