Mesozoic periods

The Mesozoic Era (251.9 to 66 million years ago) was the "Age of Reptiles." During the Mesozoic, Pangaea began separating into the modern continents, and the modern Rocky Mountains rose. Dinosaurs, crocodiles, and pterosaurs ruled the land and air. As climate changed and rapid plate tectonics resulted in shallow ocean basins, sea levels rose ...

Mesozoic periods. Division of Mesozoic era. The Mesozoic Era is divided into three time periods. These are;. The Triassic Period,; The Jurassic Period, and ...

There are three geological periods that make up the Mesozoic Era, and they are the Triassic, Jurassic and Cretaceous periods. The Triassic Period of the Mesozoic Era lasted 50.6 million years (251.902 to 201.3 million years ago). The Jurassic Period of the Mesozoic Era lasted 56 million years (201.3 to 145 million years ago).

Collector: Grandstaff Search this Place: Bollinger County, Missouri, United States, North America Taxonomy: Animalia Chordata Vertebrata Sauropsida Reptilia Archosauria Dinosauria Ornithischia Ornithopoda Hadrosauridae19.iv) Cretaceous It is a period of Mesozoic era which lasted from 150 million years ago to 65.5 million years ago. It marked the end of the Mesozoic Era and the beginning of the Cenozoic Era. All of the dinosaurs and half of the other animals & plants went extinct in this period.Geologic Time Scale. Humans subdivide time into useable units such as our calendar year, months, weeks, and days; geologists also subdivide time. They have created a tool for measuring geologic time, breaking it into useable, understandable segments. For the purposes of geology, the “calendar” is the geologic time scale.Earth’s hottest periods—the Hadean, the late Neoproterozoic, the Cretaceous Hot Greenhouse, the PETM—occurred before humans existed. Those ancient climates would have been like nothing our species has ever seen. Modern human civilization, with its permanent agriculture and settlements, has developed over just the …Three periods of late Mesozoic magmatism, including stage 1 (170-145Ma), stage 2 (145-125Ma), and stage 3 (125-90Ma), can be distinguished based on systematic zircon U-Pb ages that become progressively younger towards the SE. Stage 1 granitic rocks are predominantly I-type granitoids, but minor S- or A-type rocks also occur. ...Mesozoic periods name origin. Triassic-- whenever German geologist Friedrich August von Alberti would study rocks from what we now call the Triassic (in 1834), he would find three layers in ...The Mesozoic Era (251.9 to 66.0 million years ago) was the "Age of Reptiles." During the Mesozoic, Pangaea began separating into the modern continents, and the modern Rocky Mountains rose. Dinosaurs, crocodiles, and pterosaurs ruled the land and air.

Ever wonder why the dinosaurs disappeared? HHMI BioInteractive investigates the cause of the mass extinction at the end of the Cretaceous period—and the clue...Mesozoic Era. The amber specimen HPG-15-1 (Hupoge Amber Museum, China) is quite large, about 9cm long, while the hatchling is small, about 6cm from snout to tail, including...Mesozoic Era (248 to 65 mya) Cretaceous (144 to 65 mya) Jurassic (206 to 144 mya) Triassic (248 to 206 mya) Paleozoic Era (543 to 248 mya) Permian (290 to 248 mya) Carboniferous (354 to 290 mya) Pennsylvanian (323 to 290 mya) Mississippian (354 to 323 mya) Devonian (417 to 354 mya) Silurian (443 to 417 mya) Ordovician (490 to 443 mya)The Mesozoic is subdivided into three periods: the Triassic, Jurassic and Cretaceous. Triassic Period. The Triassic ranges from 252 million to 201 million years ago. The Triassic is mostly a transitional recovery period between the desolate aftermath of the Permian Extinction and the lush Jurassic Period. It has three major epochs: ...Apr 10, 2022 · The Mesozoic era is an era of time between the Paleozoic and Cenozoic eras. The Cenozoic is the current era humans live in. The Mesozoic era is divided into three periods - the Triassic, Jurassic ... The Triassic Period, the youngest period of the Mesozoic Era, was the time in which both mammals and dinosaurs evolved. The Mesozoic ended with a major extinction at the close of the Cretaceous Period. All dinosaurs except birds disappeared in this extinction. Another mass extinction occurred near the end of the Triassic Period. The Cenozoic ... The basic rule for the capitalization of periods and events is to capitalize specific names but not general terms. If a general time period uses a proper noun, capitalize only the proper noun. Typically, these refer to periods of human history, as opposed to geological and archaeological periods, in which words like era or age are part of the ...Mesozoic Era. The Permian Extinction. After the Permian Extinction wiped out over 95% of ocean-dwelling species and 70% of land species, the new Mesozoic Era began ... The Paleozoic Era. The Jurassic Period. Land Animals. The Mesozoic Era.

Jurassic. The Jurassic period is the second of the three divisions of the Mesozoic era, "The Age of Reptiles."The Jurassic lasted for 64 million years, from about 208 to 144 million years ago. The period is named for rock strata found in the Jura Mountains on the border between Switzerland and France.. During the Jurassic, the …15 Okt 1998 ... ... Mesozoic Era in. Dinosaurs of Australia and New Zealand and Other Animals of the Mesozoic Era. John A. Long. Product Details. HARDCOVER. $89.00 ...The period dated between 250 and 65 million years ago. Many species evolved during the Mesozoic era to replace the ones that went extinct in the previous era. The humid and tropical climate of the Mesozoic era leads to the growth of many types of plants. Another incident that marks the Mesozoic period is the evolution of the …At least two Tethyan seas successively occupied the area between Laurasia and Gondwana during the Mesozoic Era. The first, called the Paleo-Tethys Sea, or Paleo-Tethys Ocean, was created during the convergence of all landmasses into what would become the supercontinent of Pangea late in the Paleozoic Era. During the Permian and …

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Evolution of Gymnosperms. Figure 26.1 B. 1: Seed ferns: This fossilized leaf is from Glossopteris, a seed fern that thrived during the Permian age (290–240 million years ago). The fossil plant Elkinsia polymorpha, a “seed fern” from the Devonian period (about 400 million years ago) is considered the earliest seed plant known to date.groups of stick insects from two Mesozoic periods, ... Mesozoic insect fossils reveal the early evolution of twig mimicry, Science Bulletin (2022). DOI: 10.1016/j.scib.2022.07.007The Mesozoic Era is divided up into the Triassic, Jurassic, and Cretaceous periods. New research suggests that reptiles that lived during the Dinosaur age were hard-hit. Here, the carnivorous lizard Palaeosaniwa chases a pair of young Edmontosaurus while the snake Cerberophis and the lizard Obamadon look on. Credit: Carl Buell Life and climate1 / 11. The Jurassic period (199.6 million to 145.5 million years ago) was characterized by a warm, wet climate that gave rise to lush vegetation and abundant life. Many new dinosaurs emerged—in ...Quaternary Period: 2.6 to 0 Ma. The earliest geologic time scale had four intervals: Primary (first), Secondary (second), Tertiary (third), and Quaternary (fourth). Only the Quaternary remains a valid period. Epochs include the Pleistocene and the Holocene. Fossil Record: Extinction of numerous megafauna. Origin of Homo. Earth History:

... Mesozoic age fossils. During the last part of the Mesozoic (called the Cretaceous period) the climate warmed very much. Earth was several degrees warmer ...Geologic Time Scale. Humans subdivide time into useable units such as our calendar year, months, weeks, and days; geologists also subdivide time. They have created a tool for measuring geologic time, breaking it into useable, understandable segments. For the purposes of geology, the “calendar” is the geologic time scale.All periods are different. But if your period is suddenly different from what you usually experience, then you should talk to your doctor. Here are some abnormal period symptoms you shouldn't ignore. Periods are like snowflakes, no two are ...The Triassic Period (252-201 million years ago) began after Earth's worst-ever extinction event devastated life. The Permian-Triassic extinction event, also known as the Great Dying, took place roughly 252 million years ago and was one of the most significant events in the history of our planet. It represents the divide between the Palaeozoic ...Tertiary Period, former official interval of geologic time lasting from approximately 66 million to 2.6 million years ago. It is the traditional name for the first of two periods in the Cenozoic Era (66 million years ago to the present); the second is the Quaternary Period (2.6 million years ago to the present).During the Mesozoic periods, a 1,300 km wide intra-land orogenic belt was formed (Liu et al., 2013). The area has been influenced by multiple phases of tectonic movements including the Caledonian, Indo-Chinese, and Yanshan phases, resulting in distributions of large areas of Mesozoic igneous rocks . Typical igneous rocks include …The Cretaceous Period: 145 to 66 million years ago The Atlantic Ocean continued to lengthen and widen, particularly to the south, which split South America from Africa. India separated and became an island continent. Much of each continent was covered with shallow continental oceans and inland seas. ...Jan 20, 2019 · Ages of the Dinosaurs (The Mesozoic Era) This chart is a simple overview of the Triassic, Jurassic, and Cretaceous periods, all of which were part of the Mesozoic era. In brief, this incredibly long period of time, measured in "mya" or "millions of years ago," saw the development of dinosaurs, marine reptiles, fish, mammals, flying animals ... Dec 8, 2022 · 21. Birds are the only dinosaurs to have survived the Mesozoic mass extinction event, 65 million years ago. 22. The sudden extinction event end of the Mesozoic era signaled the beginning of the Cenozoic period; this is the era we are in right now and is often called the age of mammals. 23. The Mesozoic Era was the second of Earth's three major geologic eras during the Phanerozoic period. It gets its name from the Greek word for "middle life." The Mesozoic Era began 252.2 million years ago, when the Paleozoic Era ended, and ended 66 million years ago, with the start of the Cenozoic Era.The Four Eras of the Geologic Time Scale Precambrian Time: 4.6 billion to 542 Million Years Ago. Precambrian Time started at the beginning of the Earth 4.6...

The Mesozoic Era (252–66 Ma) spread over an interesting time that witnessed splitting of the Pangaea supercontinent and the opening and spreading of the Atlantic and Indian oceans. It brackets the time interval sandwiched between two extreme events of biodiversity crisis i.e., the end Permian mass extinction (around 252 Ma) marking the base ...

Historical periods, eras, and ages. Long, distinct periods in history carry specific names. These time periods are generally bound by historical events or cultural movements and practices. While some …The Phanerozoic Eon (Greek: period of well-displayed life) marks the appearance in the fossil record of abundant, shell-forming and/or trace-making organisms. It is subdivided into three eras, the Paleozoic, Mesozoic and Cenozoic, with major mass extinctions at division points. Palaeozoic Era This section needs ...The Mesozoic Era (251.9 to 66.0 million years ago) was the "Age of Reptiles." During the Mesozoic, Pangaea began separating into the modern continents, and the modern Rocky Mountains rose. Dinosaurs, crocodiles, and pterosaurs ruled the land and air. You may be familiar with the chemical periodic table from school, but there’s more than meets the eye with this seemingly simple scientific chart. Learn more about the periodic table, including how it was developed and which elements have s...The Cretaceous ( IPA: / krɪˈteɪʃəs / krih-TAY-shəs) [2] is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of the entire Phanerozoic. The name is derived from the Latin ...The boundary between the Paleozoic and Mesozoic eras and the Permian and Triassic periods is marked by the first occurrence of the conodont Hindeodus parvus. This is the first biostratigraphic event found worldwide that is associated with the beginning of the recovery following the end-Permian mass extinctions and environmental changes.21. Birds are the only dinosaurs to have survived the Mesozoic mass extinction event, 65 million years ago. 22. The sudden extinction event end of the Mesozoic era signaled the beginning of the Cenozoic period; this is the era we are in right now and is often called the age of mammals. 23.Australia - Mesozoic, Cenozoic, Ecosystems: The coal measures of the Permian gave way to barren red beds in the early part of the Triassic Period (about 252 to 247 million years ago). By 230 million years ago the foreland basin of eastern Australia had been overthrusted by the mountain belt, and a second epoch of black-coal formation opened in eastern …

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Tertiary Period, former official interval of geologic time lasting from approximately 66 million to 2.6 million years ago. It is the traditional name for the first of two periods in the Cenozoic Era (66 million years ago to the present); the second is the Quaternary Period (2.6 million years ago to the present).During the Mesozoic Era much of the plankton that exist today evolved. Coccolithophorids, microscopic plankton with calcium carbonate skeletons, were especially abundant and diverse during the Cretaceous Period. When coccolithophorids die and accumulate on the seafloor they form limestone and chalk.The Mesozoic era includes three periods – Triassic, Jurassic and Cretaceous. Did you know that actually most of the dinosaurs featured in the Jurassic Park ...the Mesozoic, which spanned the rise, reign of reptiles, climactic extinction of the non-avian dinosaurs, the evolution of mammals and birds; and; the Cenozoic, which saw the rise of mammals. The Phanerozoic is divided into three eras: the Paleozoic, Mesozoic, and Cenozoic, which are further subdivided into 12 periods.Mesozoic Era (252 million – 66 million years ago) The Mesozoic was the Age of Reptiles. Dinosaurs, crocodiles, and pterosaurs ruled the land and air. This era can be subdivided into three periods of time: Triassic (252 to 201.3 million years ago) Jurassic (201.3 to 145 million years ago) Cretaceous (145 to 66 million years ago)Description Reviews Q&A More from Sloans Science Store Description Help your students review through the 3 periods of the Mesozoic Era. This includes timespan, conditions, continent shapes and the dinos present during this time! Total Pages 1 page Answer Key Not Included Teaching Duration 30 minutes Report this resource to TPT18 Jan 2022 ... Mesozoic Era: 251.902 - 66.0 Ma. Period, Range (Ma). Cretaceous, 145.0 ... Period to discuss them. Mammals and their Ancestors In Early Triassic ...The Mesozoic Era lasted about 180 million years, from about 245 million years ago to about 65 million years ago. The Mesozoic is divided into just three time periods: the Triassic, the Jurassic, and the Cretaceous. Since lots of things were going on in each time period, we can only summarize the events. You can learn more by going to your ...Studying the structural evolution of the piedmont fold and thrust belt is one of the most important methods to interpret the mechanism of intracontinental collision orogeny. In this study, we have discovered a long-distance large-scale thrust nappe with a width of approximately 20 km in the southwestern margin of the Santanghu Basin, which provides a good evidence for studying the Mesozoic ...Earth’s hottest periods—the Hadean, the late Neoproterozoic, the Cretaceous Hot Greenhouse, the PETM—occurred before humans existed. Those ancient climates would have been like nothing our species has ever seen. Modern human civilization, with its permanent agriculture and settlements, has developed over just the …The Mesozoic Era by Alaska, released 28 June 2010 1. Nova's 2. Dolorous with Robert Manos 3. Celsius 4. Denali's Realm 5. Sundog with Kirsty Hawkshaw 6. ….

15.4: Prehistoric Climate Change. Over Earth history, the climate has changed a lot. For example, during the Mesozoic Era, the Age of Dinosaurs, the climate was much warmer and carbon dioxide was abundant in the atmosphere. However, throughout the Cenozoic Era (65 Million years ago to today), the climate has been …Amazon.com: The Mesozoic Era: Age of Dinosaurs (The Geologic History of Earth): 9781615301034: Rafferty, John P.: Books.The Mesozoic Era was a time of great change. The ancestors of major plant and animal groups that exist today first appeared during the Mesozoic, and the generally warm and habitable environment of the era supported great diversity of life-forms. However, the era is best known as the time of the dinosaurs. The Mesozoic Era began 252 million ... This ancestral lineage transitioned from marine environments to colonize new freshwater habitats during the Mesozoic era, which occurred approximately 252 to 66 million years ago. This period ...This book journeys to an era long before humans, where dinosaurs were once masters of land, sky, and sea. In addition to accounts of significant dinosaur ...Mesozoic Era (248 to 65 mya) Cretaceous (144 to 65 mya) Jurassic (206 to 144 mya) Triassic (248 to 206 mya) Paleozoic Era (543 to 248 mya) Permian (290 to 248 mya) Carboniferous (354 to 290 mya) Pennsylvanian (323 to 290 mya) Mississippian (354 to 323 mya) Devonian (417 to 354 mya) Silurian (443 to 417 mya) Ordovician (490 to 443 mya)The Mesozoic Era is literally the era of “middle life.”. It is also known as the age of dinosaurs. It lasted from 245 to 65 million years ago and is divided into the three periods described in Figure below. The Mesozoic began with the supercontinent Pangaea. Then, during the era, Pangaea broke up and the continents drifted apart.The topic of this week's lecture is the Mesozoic geologic history of the Pacific Northwest. The Mesozoic era began 252 million years ago, following the assembly of the supercontinent Pangaea and the greatest mass extinction the world has ever known. That set the stage for the beginning of the Triassic period, the first period of the Mesozoic era.... Mesozoic age fossils. During the last part of the Mesozoic (called the Cretaceous period) the climate warmed very much. Earth was several degrees warmer ...Description Reviews Q&A More from Sloans Science Store Description Help your students review through the 3 periods of the Mesozoic Era. This includes timespan, conditions, continent shapes and the dinos present during this time! Total Pages 1 page Answer Key Not Included Teaching Duration 30 minutes Report this resource to TPT Mesozoic periods, Oct 26, 2020 · The time scale is divided into four large periods of time—the Cenozoic Era, Mesozoic Era, Paleozoic Era, and The Precambrian. Cenozoic Era. The Cenozoic Era (66 million years ago through today) is the "Age of Mammals." Birds and mammals rose in prominence after the extinction of giant reptiles. , The Mesozoic era includes three periods – Triassic, Jurassic and Cretaceous. Did you know that actually most of the dinosaurs featured in the Jurassic Park ..., biography, specifically for Paleozoic-Mesozoic periods, when their distribution is considered to . have been throughout the globe throu gh land routes. Tasch (1987) pointed out that the Mayfly ., The earliest period of the Mesozoic Era was the Triassic period (248 - 208 million years ago), in which the first small dinosaurs and mammals developed. The Triassic began after a major extinction had wiped out …, Collector: Grandstaff Search this Place: Bollinger County, Missouri, United States, North America Taxonomy: Animalia Chordata Vertebrata Sauropsida Reptilia Archosauria Dinosauria Ornithischia Ornithopoda Hadrosauridae, During the Mesozoic Era, there were various extinctions, the largest of which occurred between the Triassic period, ... The period since the dinosaurs' extinction is known as the Cenozoic and is divided into 2 periods: the Paleogene period (which is itself divided into the Paleocene, Eocene and Oligocene epochs), and the Neogene period (which ..., Collector: Grandstaff Search this Place: Bollinger County, Missouri, United States, North America Taxonomy: Animalia Chordata Vertebrata Sauropsida Reptilia Archosauria Dinosauria Ornithischia Ornithopoda Hadrosauridae, Dating of the geologic record. The geologic record is the strata (layers) of rock in the planet's crust and the science of geology is much concerned with the age and origin of all rocks to determine the history and formation of Earth and to understand the forces that have acted upon it. Geologic time is the timescale used to calculate dates in the planet's geologic …, The Mesozoic Era. The Mesozoic Era is commonly subdivided into three geologic periods: . Triassic (252 to 201.3 million years ago) Jurassic (201.3 to 145 million years ago) Cretaceous (145 to 66 ..., 19.iv) Cretaceous It is a period of Mesozoic era which lasted from 150 million years ago to 65.5 million years ago. It marked the end of the Mesozoic Era and the beginning of the Cenozoic Era. All of the dinosaurs and half of the other animals & plants went extinct in this period., Phanerozoic Eon, the span of geologic time extending about 541 million years from the end of the Proterozoic Eon (which began about 2.5 billion years ago) to the present. The Phanerozoic, the eon of visible life, is divided into three major spans of time largely on the basis of characteristic assemblages of life-forms: the Paleozoic (541 million …, Sep 29, 2023 · Triassic Period, in geologic time, the first period of the Mesozoic Era, lasting from 252 million to 201 million years ago. It marked the beginning of major changes that were to take place throughout the Mesozoic Era, particularly in the evolution of life and the distribution of continents and living things. , The period dated between 250 and 65 million years ago. Many species evolved during the Mesozoic era to replace the ones that went extinct in the previous era. The humid and tropical climate of the Mesozoic era leads to the growth of many types of plants. Another incident that marks the Mesozoic period is the evolution of the …, Triassic Period (240 to 208 million years ago) At the beginning of the Mesozoic Era, the “supercontinent” began to break up. Deserts covered part of the interior, but shallow seas re-invaded the lowlands. Reptiles evolved rapidly, and two important new groups appeared. Therapsids (mammal-like reptiles) gave rise to true mammals by the end ... , Triassic Time Span. Date range: 251.9 million years ago–201.3 million years ago. Length: 51.4 million years (1.1% of geologic time) Geologic calendar: December 12 (1 AM)–December 16 (1 AM) (4 days) Triassic age trace fossil of a horseshoe crab ( Kouphichnium isp.), Petrified Forest National Park, Arizona. NPS image., The Mesozoic Era began approximately 252 million years ago at the close of the Paleozoic Era and ended 66 million years ago at the dawn of the Cenozoic Era. The Mesozoic is best known as the time of the dinosaurs. Dinosaurs first appeared early in the Mesozoic and came to dominate life on Earth throughout the rest of the era. The Mesozoic is ... , ... Mesozoic age fossils. During the last part of the Mesozoic (called the Cretaceous period) the climate warmed very much. Earth was several degrees warmer ..., The Mesozoic Era lasted about 180 million years, from about 245 million years ago to about 65 million years ago. The Mesozoic is divided into just three time periods: the Triassic, the Jurassic, and the Cretaceous. Since lots of things were going on in each time period, we can only summarize the events. You can learn more by going to your ..., Dinosaurs. The prehistoric reptiles known as dinosaurs arose during the Middle to Late Triassic Period of the Mesozoic Era, some 230 million years ago. They were members of a subclass of reptiles ..., For example, the Devonian Period is known as the 'Age of Fishes', as fish began to flourish at this stage. However, the end of the Devonian was marked by the predominance of a different life form, ... The Mesozoic Era (252 - 66 million years ago) The Holocene Epoch (10,000 years ago to the present) Wave Rock., The Triassic Period is the first of the three periods that make up the Mesozoic Era (just as years can be divided into months, eras can be divided into periods). It began 251.9 million years ago (Mya), and ended 201.3 Mya. It was preceded by the Permian Period and followed by the Jurassic Period. The Triassic Period lasted around …, A. The unconformity is younger than the fossil ages on the tilted bed. B. The unconformity is older than the fossil ages in layers above the unconformity. C. The amount of time represented by the unconformity can be approximately bracketed by the ages of the fossils above and below. D. all of these E. a and b only., The Mesozoic Era is the geological period between 252 million and 66 million years ago and is subdivided into three epochs: the Triassic, Jurassic, and …, Spinosaurus was the biggest of all the carnivorous dinosaurs, larger than Tyrannosaurus and Giganotosaurus. It lived during part of the Cretaceous period, about 112 million to 97 million years ago ..., The Mesozoic Era contains three geologic time periods including the Triassic Period (250 mya to approximately 206 mya), Jurassic Period (206 mya to …, The Precambrian, Paleozoic, Mesozoic, and Cenozoic Eras. The Geologic Time Scale is the history of the Earth broken down into four spans of time marked by various events, such as the emergence of certain species, their evolution, and their extinction, that help distinguish one era from another. Strictly speaking, Precambrian Time is not an ..., Dec 8, 2022 · 21. Birds are the only dinosaurs to have survived the Mesozoic mass extinction event, 65 million years ago. 22. The sudden extinction event end of the Mesozoic era signaled the beginning of the Cenozoic period; this is the era we are in right now and is often called the age of mammals. 23. , Dec 3, 2021 · Mesozoic: An era in geologic history that contained three related periods which became renowned for their large reptiles: the Triassic (which spanned from 251 to 199.6 million years ago), the Jurassic (which spanned from 199.6 to 145.5 million years ago), and the Cretaceous (which spanned from 145.5 to 65.5 million years ago). , Pregnancy is the most common reason for a missed period, but it’s not the only reason. In this video, SciShow explains a few other reasons you might skip a period. Pregnancy is the most common reason for a missed period, but it’s not the on..., Spanning around 200 million years, the Mesozoic Era was characterized by rapid evolution of life on the Earth, most noteworthy being the rise and fall of the dinosaurs. In the plant kingdom, the flowering plants appeared for the first time. Read this ScienceStruck article to know more about various characteristics of this era, like the plants, animals, climatic conditions, and major events., Geologic periods. Triassic. The Triassic ranges roughly from 252 million to 201 million years ago, preceding the Jurassic Period. The period is bracketed between the ... Jurassic. Cretaceous.… See more, The Mesozoic Era spanned 252 to 66 million years ago – a tiny part of the Earth’s long history., Cretaceous Period, Mesozoic Era, Phanerozoic Eon [145 Myr - 66 Myr ] The Cretaceous Period is perhaps most familiar because of the major extinction event which marks the Cretaceous-Tertiary boundary. It is typically called the K-T extinction, using the first letter of the German spelling of Cretaceous, and it marked the end of the dinosaurs.