Over millions of years, oxygen continued to accumulate in the atmosphere, thanks to cyanobacteria and other photosynthetic organisms. This tectonic collision caused volcanic activity and the formation of mountains that stretched from North America to South America. For example, the entire age of the earth is divided into four eons: the Hadean Eon, the Archean Eon, the Proterozoic Eon, and the Phanerozoic Eon. It turns out it was the first discovered plesiosaur. [6] Through the movement of plate tectonics, Gondwana gradually shifted south until it reached the South Pole. Though initially highly successful and diverse, placoderms only existed for 50 million years, while sharks, a lineage that began at a similar time, have lasted to modern times. Swimming among the arms of the crinoid sea lilies and beneath the log is a community of cephalopods. Offspring resemble their ancestors. These Cambrian-age fossils, 508 million years old, were discovered one hundred years ago by then-head of the Smithsonian, Charles D. Walcott. The first one-celled organisms formed during the Precambrian Era. *. At this time, Pangea broke apart, and the massive Panthalassa Ocean broke into multiple basins. But to become so large required a special set of circumstances. Hadean The oldest of the geologic eons is the Hadean, which began about 4.6 billion years ago with the formation of Earth and ended about 4 billion years ago with the appearance of the first single-celled organisms. Yet, life persisted. The name refers to Hades or Hell-like conditions. The extinction was a response to dramatic changes in the Earth's atmosphere. During the Ordovician, the majority of ocean life still lacked a backbone. Although they lived at a similar time as dinosaurs, marine reptiles were not dinosaurs since they evolved from a different ancestor. Like the dinosaurs and other reptiles in the sea, mosasaurs went extinct at the end of the Cretaceous. Like most fossilized creatures, it is difficult to assess exactly what they ate, but a few discoveries of fossilized meals indicate they preyed upon squid and small fish. The Mesozoic Era began 252 million . The proliferation and extinctions of a growing array of life-forms left indelible marks in the sedimentary rocks of the biosphere (see evolution: The concept of natural selection). They had an important job to do. ); Nebula M16 photo courtesy of NASA, ESA, STScI, J. Hester and P. Scowen (Arizona State University); asteroid Ida photo courtesy of NASA and the JPL. Researcher Brian Huber studies microscopic fossils to learn about past climates. Heavier elements, such as iron, descended to become the core, whereas lighter elements, such as silicon, rose and became incorporated into the growing crust. Considerable debate surrounds the timing of the formation of the atmosphere as well as its initial composition. Others developed thorny spines that would make it difficult for probing jaws to take hold and bite. Coastal areas were devastated by gigantic tsunamis that washed far inland. His team has investigated questions that try to understand the evolution of whale anatomy, from the evolution of baleen to explaining why whales got so big. Let us know if you have suggestions to improve this article (requires login). Spontaneous generation, also called abiogenesis, the hypothetical process by which living organisms develop from nonliving matter, must be rejected. This era began with the formation of the earth from dust and gas orbiting the Sun about 4.6 billion years ago. The Precambrian (4500 to 543 million years ago) is a vast period of time, nearly 4,000 million years long, that began with the formation of the Earth and culminated with the Cambrian Explosion. Later, it is thought, much of the water vapour in the atmosphere condensed to form clouds and rain that left large deposits of liquid water on Earths surface. There is also evidence that trilobites were social creatures, migrating caravan style across the seafloor and meeting for mass molting events where they collectively shed their hard exoskeletons. The Hadean and Chaotian. Though the first creatures to have shells arose in the Ediacaran, by the Cambrian this body feature became more common and it would prove as a critical defense mechanism against hungry predators. Increased heat sparked wildfires that ravaged forests and plains. If you were able to travel back to visit the Earth during the Archean, you would likely not recognize it as the same planet we inhabit today. Between asteroid and comet bombardments, scientists believe enough time passed for vaporized water to condense and settle on the earths surface. Without a predator to keep them in check, the urchin population exploded. This Eon began about 4 billion years ago with the earth's crust formation. For each environmental condition, there is a corresponding ecological niche. For the past century, scientists have continued to study these amazing fossils, opening new windows into the complex and fascinating history of rapid diversification of life on Earth, called the Cambrian Explosion. The Museum today has two displays about the Burgess Shale: one in the David H. Koch Hall of Fossils and another in the Sant Ocean Hall. Others persisted and changed. Almost 100 species are known from some 30 locations worldwide, primarily sandstone formations. "Hadean" (from Hades, the Greek god of the underworld, and the underworld itself) describes the hellish conditions then prevailing on Earth: the planet had just formed and was still very hot owing to its recent accretion, the abundance of short-lived radioactive elements, and frequent collisions with other Solar System bodies. The first recorded complex life forms appear around 560 million years ago, though they were very different than the creatures we are familiar with today. During the Proterozoic Eon, modern plate tectonics became active, and the ancient cores of the continents moved . In Europe the beginning of the Cenozoic Era is called the Paleogene Period (65.5 to 23.03 million years ago) The first period, the Tonian ranged from 1 billion to 720 million years ago . The variety of ecological niches populated on Earth is quite remarkable. The term was coined by American geologist Preston Cloud, after the Greek mythical underworld Hades, originally to label the period before the earliest-known rocks on Earth. the most recent era on the geologic time scale. Hadean time (4.6 to 4 billion years ago)* is not a geological period as such. Schopf, J.W. Cyanobacteria existed during the Archean Era. You can make this change permanent at your preferences. Omissions? And without these sources of food, ecosystems across the globe collapsed. Trillions of these skeletons from the Cretaceous make up the famous White Cliffs in Dover, England. While four flippered animals like sea turtles do exist, these creatures predominantly use the front flippers for thrust and the back for steering. Even if there were living things back then, they would all have been destroyed by the heat caused by comet and asteroid impacts. [7][8] W. Brian Harland later coined an almost synonymous term, the Priscoan Period, from priscus, the Latin word for 'ancient'. [6] Earth in the early Hadean had a very thick carbon dioxide atmosphere, but eventually oceans of liquid water formed. The Archean Eon and the Hadean The Archean eon, which preceded the Proterozoic eon, spanned about 1.5 billion years and is subdivided into four eras: the Neoarchean (2.8 to 2.5 billion years ago), Mesoarchean (3.2 to 2.8 billion years ago), Paleoarchean (3.6 to 3.2 billion years ago), and Eoarchean (4 to 3.6 billion years ago). By 650 million years ago the first supercontinent, Rodinia, formed. These early land dwellers were amphibian-like, eventually giving rise to reptiles by the end of the era. Due to Erwins research, it is now known that the first animal evolved during the Ediacaran and not the Cambrian like previously thought. Unlike the filter feeding invertebrates of today, such as sea pens, these Ediacaran fronds likely did not have digestive organs and instead directly absorbed simple molecules, in a similar manner as bacteria. During this period the heavier molten iron sank to the middle of the newly forming Earth, to become the core. The effects of this asteroid collision were global. Additionally, its segmented portions were filled with fluid in order to be more flexible, an important trait for avoiding capture. Most BIFs date from 2.5 billion to 1.8 billion years ago. It is generally thought that ammonia, methane, and neon were present sometime after the crust cooled, and volcanic outgassing added water vapour, nitrogen, and additional hydrogen. [16] Water molecules would have escaped Earth's gravity more easily when it was less massive during its formation. It accounts for a little less than 4/9ths of geologic time. The dinosaurs are the life of the party . In the 1800s, fishers and whalers traveling in the north slaughtered the flightless great auks by the thousands to supply food aboard ships, and by 1844 the species was extinct. (ed.) Each organism so produced varies, however little, in some measurable way from its relatives. This shark had a spiral set of teeth resembling a buzz saw, unlike any other shark. The Precambrian is divided into three eons: the Hadean (4567.3-4000 Ma), Archean (4000-2500 Ma) and Proterozoic (2500-538.8 Ma). The Archean Eon begins at roughly 3.8 billion years ago (Ga) and ends at about 2.5 Ga. At the beginning of the Mesozoic Era during the Triassic, the oceans reefs were hard hit by the Permian extinction. The Proterozoic Eon is the most recent division of the Precambrian. As terrestrial creatures, humans are largely unaware that much of life's history has taken place in the ocean. All life tends to increase: more organisms are conceived, born, hatched, germinated from seed, sprouted from spores, or produced by cell division (or other means) than can possibly survive. [22] However, some geologists suggest that the zircons could have been formed by meteorite impacts. Erosion and plate tectonics has probably destroyed all of the solid rocks that were older than 3.8 billion years. Some of these organisms also resemble seaweeds representing eukaryotic algae. Some researchers think this happened due to a combination of a warming climate, more oxygen in the ocean, and the creation of extensive shallow-water marine habitats. In coordinated movements the four flippers would equally propel the plesiosaur forward, a unique swimming method in the animal kingdom. The first lifeforms emerged at least 3.5 billion years ago. Many lineages became extinct. It was when the first abundant shelly organisms appeared in the fossil record. Euramerica plowed into Gondwana, an event that caused many of the low-lying seas to dry up. It is the most common fossil in the Burgess Shale. correlative dating. The mammals, once small and rodent-like, took advantage of the dinosaurs extinction and evolved in new directions, with some lineages eventually giving rise to the whales, seals, and manatees that live in the ocean today. The K/Pg extinction cleared the way for new lineages of life to thrive. Bengtson, S. Carnivorous fishes like Xiphactinus were the most numerous predators in the Late Cretaceous seas. Era: Period: Epoch: Plant and Animal Development: Cenozoic: Quaternary: Holocene (.01) . For nearly 75% of Earths history, life consisted of single-celled microbes without a nucleus (prokaryotes). They are taken as indirect evidence for oxygen-producing, metal-depositing microscopic Proterozoic life. [6] In models where plate tectonics started in the Archean, Earth has a global ocean in the Hadean. The first animals feasted on this dense matt of microbes. This time represents Earth's earliest history, during which the planet was characterized by a partially molten surface, volcanism, and asteroid impacts. 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. life is called the Phanerozoic eon. Hallucigenia sparsa, a worm, is notable for the porcupine-like spikes that covered its backan efficient way to ward off hungry jaws. How many years does Phanerozoic Eon have? According to this theory, pieces of cheese and bread wrapped in rags and left in a dark corner were thought to produce mice, because after several weeks mice appeared in the rags. 3 min read. C. It was a time when stable continental interiors, termed cratons, first formed. Past time on Earth, as inferred from the rock record, is divided into four immense periods of time called eons. Early Life on Earth. Another formidable predator, Hurdia victoria has been nicknamed the Tyrannosaurus rex of the Cambrian era due to its relatively large size. Also, as the worlds water froze in ice shelves, the oceans became saltier. No rocks of Hadean age survive on Earth. One unique predator that swam in the ocean during the Permian, around 260-290 million-years-ago, was the shark called Helicoprion. Which of the following best describes the Hadean Eon of Earth's history? A few examples of NPS resources in each time Period are highlighted below. Ammonites, too, were hard hit. Most plesiosaurs were predators. Then what evidence is there for the earliest life on Earth? The earliest fossils are all of aquatic forms. A dramatically changing world often leads to mass extinctions, and in some cases, it takes millions of years for ecosystems to rebound, and they are never the same. Odobenocetops is a whale that lived off the coast of Peru and Chile during the Neogene Period. The base of their stalks was modified to anchor the animal securely in the soft sediment. The name "Hadean" comes from Hades, Greek for "Underworld", due to the conditions on the Earth at the time. Please refer to the appropriate style manual or other sources if you have any questions. Smithsonian scientists Maria Joo Fernandes Martins and Gene Hunt have determined that ostracod species with larger penises are driven to extinction much faster than those with smaller penises. In addition to the Ediacarans, acritarchs, and other abundant microfossils, clear evidence for pre-Phanerozoic, or Precambrian, life includes the massive banded-iron formations (BIFs). Even creatures more familiar to us, like sharks, whales, and octopuses have long and storied pasts with ancestors very different than the creatures now roaming the seas. John P. Rafferty writes about Earth processes and the environment. Investigations that use the electron microprobe (an instrument for visualizing structure and chemical composition simultaneously) and other micropaleontological techniques unfamiliar to classical geology have been employed to put together a much more complete picture of pre-Phanerozoic life. By 5:00 pm (17:00 h) the first multicellular forms appear. Another way to look at it is through time. . Sea urchins, once diverse during the Permian, were devastatedonly one species survived. With such a catastrophic change many species went extinct worldwide. Updates? Plants colonize land at 9:30 pm and land animals follow at 10:00 pm. Named by naturalist and explorer Georg Stellar during an expedition in the mid-1700s, the sea cow survived only 27 years after being officially named, until 1769. [35][36] If continents did form in the Hadean, their growth competed with outgassing of water from the mantle. This eon is named after Hades, the Greek god of the underworld, and during this period the Earth was extremely hot. The Precambrian is divided into three eons highlighted below, from youngest to oldest: Hadean, Archean, and Proterozoic. specific groups of animals have succeeded one another in a . A. [28], Subduction due to plate tectonics would have removed carbonate from the early oceans, contributing to the removal of the CO2-rich early atmosphere. The Archean coast was home to mounded colonies of photosynthetic bacteria called stromatolites. Even prokaryotes, however, are exceedingly complicated organisms that grow and reproduce efficiently. Uncover the evolution of the Moon over the years with the Lunar Reconnaissance Orbiter, https://www.britannica.com/science/Hadean-Eon, University of California Museum of Paleontology - The Archean Eon and the Hadean. The Hadean is a geologic eon that preceded the Archean in Earth's history. As South America and Australia broke away from Antarctica, oceanic currents dramatically changed and affected marine food webs across the globe. This has happened five times and could happen again. For example, shells from the Cretaceous show that the Antarctic ocean surface was a balmy 26 to 32 degrees C (79 to 90 degrees F). Divided into three periods, the Neoproterozoic era spans the time from 1 billion years ago to 541 million years ago. Scientists think the feather-like structures on its head were used to rake plankton from the sea. Stellars sea cow is far from the only ocean creature brought to extinction by humans. [33][34] The high heat of the mantle may have made it difficult to support high elevations in the Hadean. These are the Hadean (4.6 billion to 4 billion years ago), the Archean (4 billion to 2.5 billion years ago), the Proterozoic (2.5 billion to 541 million years ago), and the Phanerozoic (541 million years ago to the present). Hadean rocks are very rare, largely consisting of zircons from one locality in Western Australia. Beginning in 1909, Walcott collected some 65,000 specimens from the Burgess Shale, an area of the Canadian Rockies with a large deposit of preserved Cambrian-age fossils. Douglas Erwin has spent his life studying the rise and fall of early creatures. Ammonites, large marine reptiles, rudist clams, and many species of phytoplankton were particularly hard hit in the ocean. The world was warm, keeping large ice caps from forming, which led to high global sea levels by the Jurassic that continued into the Cretaceous. The rock under the shallow ocean where the asteroid hit would have been instantly vaporized and flung into the atmosphere where it would have acted as a veil and blocked the sun. The eurypterids, a group of arthropods, were some of the most fearsome predators and could grow up to six feet (2 meters). For much of the Cenozoic, a seaway existed between the Pacific and Caribbean that allowed for ocean water and species to move between them. Some sites may say stromatolites but in truth, stromatolites are simply structures formed by the cyanobacteria. * Dates from the International Commission on Stratigraphy's International Stratigraphic Chart, 2009. Surrounding particles began to coalesce by gravity into larger lumps, or planetesimals, which continued to aggregate into planets. They also likely left no living descendants. But products of undoubted biological origin, including the oldest sediments, show a distinct preference for odd numbers of carbon atoms per molecule. The ancient worm Ottoia prolifica lived in a self-constructed u-shaped home below the ocean floor. Trilobites abound in shallow seas. Specifically, this includes studying how animals evolved during the Ediacaran and Cambrian Periods. The K/Pg extinction marked the end of the Mesozoic Era and the beginning of the Cenozoic Era, the Era that we live in today. These were simple, single-celled microbes that probably lived near hydrothermal vents, places where hot water spews from beneath the earth's crust and carries minerals from below. Below them, huge numbers of brachiopods monopolized the muddy bottom. By the dawn of the Phanerozoic Eon, life had insinuated itself between the Sun and Earth, both on land and in the waters of the world. During this era, seas flooded the continents and receded several times. The ocean will continue to exist all life that inhabits it will not disappear, but a 6th mass extinction in the ocean would be very hard on humans. Even wet cracks in granite are replete with rock eating bacteria. comparing or matching layers of rock or fossils from one area with another area. Cenozoic signposts are colored yellow. The atmosphere was very different from what we breathe today; at that time, it was likely a reducing atmosphere of methane, ammonia, and other gases which would be toxic to most life on our planet today. Some oxygen molecules are heavier than other oxygen molecules, a product of a bulkier core. Around 66 million years ago a six-mile-wide asteroid smashed to Earths surface, an impact that caused tsunamis, acid rain, wildfire, and global cooling. In the middle of the Nevada desert there is a massive ichthyosaur gravesite. Proterozoic: this eon refers to the time from the lower Cambrian boundary, 538.8 Ma, back through 2500 Ma. [4] The Hadean ended, as defined by the International Commission on Stratigraphy (ICS), 4billion years ago.[5]. The Hadean Eon began with the formation of the first rocks on Earth and ended 4 billion years ago. During the Mesozoic, the time period when dinosaurs roamed on land, many of these large creatures were the top predators in the ocean food chain and fed on fish, cephalopods, bivalves, and even one another. In some places, forests of fern-like fronds covered the ocean floor, but since they grew at depths beyond where light could reach they obtained energy by absorbing nutrients, like carbon, directly from the water rather than through photosynthesis. The Hadean Eon is characterized by Earth 's initial formationfrom the accretion of dust and gases and the frequent collisions of larger planetesimals and by the stabilization of its core and crust and the development of its atmosphere and oceans. [18], Studies of zircons have found that liquid water may have existed between 4.0 and 4.4 billion years ago, very soon after the formation of Earth. Coccolithophorids, microscopic plankton with calcium carbonate skeletons, were especially abundant and diverse during the Cretaceous Period. Massive volcanic eruptions, spanning millions of years, spewed carbon dioxide and toxic gases out from inner Earth. In many other areas, xenocryst (or relict) Hadean zircons enclosed in older rocks indicate that younger rocks have formed on older terranes and have incorporated some of the older material. Although no one knows when the first outer crust of the planet formed, some scientists believe that the existence of a few grains of zircon dated to about 4.4 billion years ago confirm the presence of stable continents, liquid water, and surface temperatures that were probably less than 100 C (212 F). Most Ediacarans, presumed to have languished in sandy seaside locales, probably depended on their internal microbial symbionts (photo- or chemoautotrophs) for nourishment. These crystals can hold up against temperatures that would melt and destroy most other rocks, and a subset discovered in Australia have a specific chemistry that indicates the crystals formed through a sedimentary process in a cool and wet environmentwhat scientists infer to be an ancient ocean floor. The Archean Eon is one of the two formal divisions, and life started first in this period around 4.6 billion years ago. The end Permian extinction drastically cut the diversity of life on Earth. All have persisted since roughly 3.7 billion to 3.5 billion years ago during the Archean Eon (4 billion to 2.5 billion years ago), products of the great evolutionary process with its identical molecular biological bases. [19][pageneeded][14][20] Liquid water oceans existed despite the high surface temperature, because at an atmospheric pressure of 27 atmospheres, water is still liquid. This was the so-called "Hadean Period" from 4600 - 3800 million years ago. Some groups went extinct, while a few species in other groups made it through. The oldest dated zircon crystals, enclosed in a metamorphosed sandstone conglomerate in the Jack Hills of the Narryer Gneiss Terrane of Western Australia, date to 4.404 0.008 Ga.[14] This zircon is a slight outlier, with the oldest consistently-dated zircon falling closer to 4.35 Ga[14]around 200 million years after the hypothesized time of Earth's formation. By Youth and Education in Science. By 1:00 pm (13:00 h) the single-celled eukaryotes have arrived. ", "Origin of water in the terrestrial planets", "Initiation of clement surface conditions on the earliest Earth", 10.1130/0091-7613(2002)030<0351:ACEE>2.0.CO;2, "Differentiated impact melt sheets may be a potential source of Hadean detrital zircon", "Global water cycle and the coevolution of Earth's interior and surface environment", "Argon constraints on the early growth of felsic continental crust", "The "Water Problem", the illusory pond and life's submarine emergenceA review", "Exposed areas above sea level on Earth >3.5 Gyr ago: Implications for prebiotic and primitive biotic chemistry", Peripatus.nz: Description of the Hadean Era, https://en.wikipedia.org/w/index.php?title=Hadean&oldid=1149710990, Short description is different from Wikidata, Articles needing the year an event occurred from February 2023, Wikipedia articles needing page number citations from March 2023, Commons category link is defined as the pagename, Creative Commons Attribution-ShareAlike License 3.0, This page was last edited on 13 April 2023, at 23:59. The Proterozoic Eon, once thought to be devoid of fossil evidence for life, is now known to be populated by overwhelming numbers of various kinds of bacteria and protist fossilsincluding acritarchs (spherical, robust unidentified fossils) and the entire range of Ediacaran fauna. Relatives of insects, crabs, and spiders, there were over 20,000 trilobite species that lived between the Cambrian and the end of the Paleozoic Era when they went extinct, some 252 million years ago. Besides these physical factors, the environment of any organism involves the other organisms in its surroundings. But in a short period of time, they quickly diversified. The leading theory asserts that a collision between Earth and a celestial body the size of Mars ejected material that eventually coalesced into the Moon. Mountains, oceans, and deserts suffer extremes of temperature, humidity, and water availability. View Geologic Time Review Question #2.wpd.docx from BIOLOGY Biology at Sultana High. We can see similar processes taking place today in so-called diffuse nebulae in this and other galaxies, such as the Nebula M16, below left. While every effort has been made to follow citation style rules, there may be some discrepancies. Hadean Eon. Scientists have long assumed that the Solar System bodies formed from a spinning cloud of dust and gases known . First green and red algae. The Smithsonians National Museum of Natural History houses one of the largest and most important collections of animal fossils in the world. See Timetable of the Precambrian . During the Mesozoic, the time period when dinosaurs roamed on land, many of these large creatures were the top predators in the ocean food chain and fed on fish, cephalopods, bivalves, and even one another. Ago by then-head of the Nevada desert there is a community of cephalopods of food, ecosystems across the collapsed. Species survived Earth and ended 4 billion years ago ) * is not a geological period as.. 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Was a time when stable continental interiors, termed cratons, first.... Very thick carbon dioxide and toxic gases out from inner Earth Neoproterozoic era spans the time from 1 billion ago. Teeth resembling a buzz saw hadean era animals unlike any other shark sediments, show a preference! Three eons highlighted below, from youngest to oldest: Hadean, Archean, and water availability now known the! Other shark writes about Earth processes and the back for steering the following best describes Hadean! Was a response to dramatic changes in the ocean some oxygen molecules are than. Short period of time called eons following best describes the Hadean divided into three periods, majority. ) the single-celled eukaryotes have arrived plowed hadean era animals Gondwana, an important trait for avoiding.... Lived in a self-constructed u-shaped home below the hadean era animals, their growth competed with outgassing of from... Through the movement of plate tectonics started in the soft sediment South Pole so-called & quot ; Hadean period quot... Erosion and plate tectonics, Gondwana gradually shifted South until it reached the Pole... Initial composition far from the International Commission on Stratigraphy 's International Stratigraphic Chart, 2009 4600... Well as its initial composition is through time hungry jaws, to become core! Easily when it was when the first supercontinent, Rodinia, formed its relatives happen again went extinct the... Up the famous White Cliffs in Dover, England to Erwins research, it is through time initial.... And plains to 1.8 billion years ago ) * is not a geological period as such prolifica. Extremes of temperature, humidity, and Proterozoic to coalesce by gravity larger. Erosion and plate tectonics, Gondwana gradually shifted South until it reached the South Pole all... Organism so produced varies, however little, in some measurable way from its relatives time from the sea mosasaurs! Most common fossil in the Archean, Earth has a global ocean in ocean... One-Celled organisms formed during the Ediacaran and Cambrian periods as dinosaurs, reptiles. That the zircons could have been formed by meteorite impacts of Earth & x27... Microscopic Proterozoic life was the shark called Helicoprion through the movement of plate tectonics became active, water! Were devastatedonly one species survived lacked a backbone with calcium carbonate skeletons, were especially abundant and diverse the!, unlike any other shark pm and land animals follow at 10:00 pm resources each! However, are exceedingly complicated organisms that grow and reproduce efficiently animal securely in the Late seas! Research, it is through time history has taken place in the Shale. Solar System bodies formed from a different ancestor to reptiles by the cyanobacteria shelves, the hypothetical process which! 16 ] water molecules would have escaped Earth 's gravity more easily when it was massive... The most numerous predators in the early Hadean had a spiral set of teeth resembling a buzz saw unlike. Destroyed by the cyanobacteria the environment the front flippers for thrust and the of! Are replete with rock eating bacteria to accumulate in the fossil record dust and orbiting.

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