“Dinosaurs went extinct before 75 million years ago.”

The Cretaceous–Palaeogene mass extinction around 66 million years ago was triggered by the Chicxulub asteroid impact on the present-day Yucatán Peninsula 1, 2. … This event caused the highly selective extinction that eliminated about 76% of species 3, 4, including all non-avian dinosaurs, pterosaurs, ammonites, rudists and most marine reptiles.Abstract The Cretaceous–Palaeogene mass extinction around 66 million years ago was triggered by the Chicxulub asteroid impact on the present-day Yucatán Peninsula 1, 2. This event caused the highly selective extinction that eliminated about 76% of species 3, 4, including all non-avian dinosaurs, pterosaurs, ammonites, rudists and most marine reptiles. The timing of the impact and its aftermath have been studied mainly on millennial timescales, leaving the season of the impact unconstrained. Here, by studying fishes that died on the day the Mesozoic era ended, we demonstrate that the impact that caused the Cretaceous–Palaeogene mass extinction took place during boreal spring. …

The Cretaceous/Paleogene mass extinction, 66 Ma, included the demise of non-avian dinosaurs. … The end-Cretaceous mass extinction, 66 Ma, is the most recent of Raup and Sepkoski’s (1) “Big Five” extinction events (2). Non-avian dinosaurs, along with many other groups that had dominated the Earth for 150 My, went extinct.Abstract The Cretaceous/Paleogene mass extinction, 66 Ma, included the demise of non-avian dinosaurs. Intense debate has focused on the relative roles of Deccan volcanism and the Chicxulub asteroid impact as kill mechanisms for this event. Here, we combine fossil-occurrence data with paleoclimate and habitat suitability models to evaluate dinosaur habitability in the wake of various asteroid impact and Deccan volcanism scenarios. Asteroid impact models generate a prolonged cold winter that suppresses potential global dinosaur habitats. … --- The end-Cretaceous mass extinction, 66 Ma, is the most recent of Raup and Sepkoski’s (1) “Big Five” extinction events (2). Non-avian dinosaurs, along with many other groups that had dominated the Earth for 150 My, went extinct. Although there is still debate as to whether dinosaurs were already in decline (3) prior to their extinction, their fossil record demonstrates global survival until the terminal Cretaceous and unambiguous absence thereafter. The Cretaceous/Paleogene (K/Pg) mass extinction coincided with two major global environmental perturbations: heightened volcanism associated with the Deccan Traps and the Chicxulub asteroid impact (Fig. 1A) (4). …

Non-avian dinosaurs went extinct 66 million years ago, geologically coincident with the impact of a large bolide (comet or asteroid) during an interval of massive volcanic eruptions and changes in temperature and sea level.ABSTRACT Non-avian dinosaurs went extinct 66 million years ago, geologically coincident with the impact of a large bolide (comet or asteroid) during an interval of massive volcanic eruptions and changes in temperature and sea level. There has long been fervent debate about how these events affected dinosaurs. We review a wealth of new data accumulated over the past two decades, provide updated and novel analyses of long-term dinosaur diversity trends during the latest Cretaceous, and discuss an emerging consensus on the extinction's tempo and causes. Little support exists for a global, long-term decline across non-avian dinosaur diversity prior to their extinction at the end of the Cretaceous. …

The large mass extinction of terrestrial and marine life—most notably, non-avian dinosaurs—occurred around 66 million years ago, at the boundary between the Cretaceous and Paleogene periods.Impact Dating The large mass extinction of terrestrial and marine life—most notably, non-avian dinosaurs—occurred around 66 million years ago, at the boundary between the Cretaceous and Paleogene periods. But attributing the cause to a large asteroid impact depends on precisely dating material from the impact with indicators of ecological stress and environmental change in the rock record. Renne et al. (p. 684; see the Perspective by Pälike) acquired high-precision radiometric dates of stratigraphic layers surrounding the boundary, demonstrating that the impact occurred within 33,000 years of the mass extinction. …

The question why non-avian dinosaurs went extinct 66 million years ago (Ma) remains unresolved because of the coarseness of the fossil record. … We analyse the speciation-extinction dynamics for six key dinosaur families, and find a decline across dinosaurs, where diversification shifted to a declining-diversity pattern ~76 Ma.Abstract The question why non-avian dinosaurs went extinct 66 million years ago (Ma) remains unresolved because of the coarseness of the fossil record. A sudden extinction caused by an asteroid is the most accepted hypothesis but it is debated whether dinosaurs were in decline or not before the impact. We analyse the speciation-extinction dynamics for six key dinosaur families, and find a decline across dinosaurs, where diversification shifted to a declining-diversity pattern ~76 Ma. We investigate the influence of ecological and physical factors, and find that the decline of dinosaurs was likely driven by global climate cooling and herbivorous diversity drop. The latter is likely due to hadrosaurs outcompeting other herbivores. We also estimate that extinction risk is related to species age during the decline, suggesting a lack of evolutionary novelty or adaptation to changing environments. …

The Cretaceous-Paleogene boundary (KPB) is defined by an elevated iridium anomaly along with other ejecta from the Chicxulub asteroid impact ca. 66 million years ago 1, 2. … The extinction of non-avian dinosaurs at the KPB is the most profound example of megafauna being abruptly removed from fluvial environments.Introduction The Cretaceous-Paleogene boundary (KPB) is defined by an elevated iridium anomaly along with other ejecta from the Chicxulub asteroid impact ca. 66 million years ago 1, 2. The causes and biotic consequences of the end-Cretaceous mass extinction (EKME) have received considerable attention 3, 4, 5, and that sudden disappearance of large swaths of the biosphere had reverberating effects on the geosphere, at least in the marine realm 6. Did the most famous victims of the EKME—dinosaur megafauna—leave a similar imprint on the continental rock record? … Disappearance of megafauna can thus abruptly restructure vegetation and terrestrial ecosystems 7, 8, consequently altering fluvial dynamics and their expression in the sedimentological record 10, 11. The extinction of non-avian dinosaurs at the KPB is the most profound example of megafauna being abruptly removed from fluvial environments. In the Western Interior of North America (Western Interior, hereafter), the disappearance of dinosaur megafauna coincides with a shift in fluvial sedimentary facies that is mappable in outcrop and thus formalized in stratigraphic nomenclature denoting contacts between uppermost Cretaceous (e.g., Lance and Hell Creek) and Paleocene (e.g., Fort Union) formations 3, 5, 12. Direct evidence of the Chicxulub asteroid impact frequently coincides with those formational contacts (Fig. …

According to the fossil record, the rule of dinosaurs came to an abrupt end ∼65 million years ago, when all nonavian dinosaurs and flying reptiles disappeared. … The Cretaceous-Paleogene boundary ~65.5 million years ago marks one of the three largest mass extinctions in the past 500 million years.The Fall of the Dinosaurs According to the fossil record, the rule of dinosaurs came to an abrupt end ∼65 million years ago, when all nonavian dinosaurs and flying reptiles disappeared. Several possible mechanisms have been suggested for this mass extinction, including a large asteroid impact and major flood volcanism. Schulte et al. (p. 1214) review how the occurrence and global distribution of a global iridium-rich deposit and impact ejecta support the hypothesis that a single asteroid impact at Chicxulub, Mexico, triggered the extinction event. Such an impact would have instantly caused devastating shock waves, a large heat pulse, and tsunamis around the globe. … ## Abstract The Cretaceous-Paleogene boundary ~65.5 million years ago marks one of the three largest mass extinctions in the past 500 million years. The extinction event coincided with a large asteroid impact at Chicxulub, Mexico, and occurred within the time of Deccan flood basalt volcanism in India. Here, we synthesize records of the global stratigraphy across this boundary to assess the proposed causes of the mass extinction. Notably, a single ejecta-rich deposit compositionally linked to the Chicxulub impact is globally distributed at the Cretaceous-Paleogene boundary. …

It has long been debated whether non-avian dinosaurs went extinct abruptly or gradually at the end-Cretaceous (66 million years ago), because their fossil record at this time is mostly limited to northern North America. We constrain a dinosaur-rich unit to the south, the Naashoibito Member in New Mexico, to the very latest Cretaceous (~66.4 to 66.0 million years), preserving some of the last-known non-avian dinosaurs. … Ecological modeling shows that North American terrestrial vertebrates maintained high diversity and endemism in the latest Cretaceous and early Paleogene, with bioprovinces shaped by temperature and geography. This counters the notion of a low-diversity cross-continental fauna and suggests that dinosaurs were diverse and partitioned into regionally distinct assemblages during the final few hundred thousand years before the end-Cretaceous asteroid impact.Abstract It has long been debated whether non-avian dinosaurs went extinct abruptly or gradually at the end-Cretaceous (66 million years ago), because their fossil record at this time is mostly limited to northern North America. We constrain a dinosaur-rich unit to the south, the Naashoibito Member in New Mexico, to the very latest Cretaceous (~66.4 to 66.0 million years), preserving some of the last-known non-avian dinosaurs. Ecological modeling shows that North American terrestrial vertebrates maintained high diversity and endemism in the latest Cretaceous and early Paleogene, with bioprovinces shaped by temperature and geography. This counters the notion of a low-diversity cross-continental fauna and suggests that dinosaurs were diverse and partitioned into regionally distinct assemblages during the final few hundred thousand years before the end-Cretaceous asteroid impact. Access the full article

It has long been debated why groups such as non-avian dinosaurs became extinct whereas mammals and other lineages survived the Cretaceous/Paleogene mass extinction 66 million years ago. … Ecological evidence (29, 65), including the multidimensional niches presented here, paints a nuanced picture of the final 18 Ma of non-avian dinosaur existence. Despite substantial food web restructuring before their extinction, non-avian dinosaurs seem to have been characterized by largely stable and mostly static ecological niches during the Campanian and Maastrichtian, likely due to a large spectrum of already inhabited ecologies and morphotypes (25, 29, 55, 60, 61).Abstract It has long been debated why groups such as non-avian dinosaurs became extinct whereas mammals and other lineages survived the Cretaceous/Paleogene mass extinction 66 million years ago. We used Markov networks, ecological niche partitioning, and Earth System models to reconstruct North American food webs and simulate ecospace occupancy before and after the extinction event. We find a shift in latest Cretaceous dinosaur faunas, as medium-sized species counterbalanced a loss of megaherbivores, but dinosaur niches were otherwise stable and static, potentially contributing to their demise. … An absence of long-term niche breadth decline in dinosaurs (29) is also supported by their highly diverse anatomies and functional abilities until the end of the Cretaceous (60–62), which would have promoted dietary and habitat niche partitioning between sympatric taxa (57, 63, 64). Ecological evidence (29, 65), including the multidimensional niches presented here, paints a nuanced picture of the final 18 Ma of non-avian dinosaur existence. Despite substantial food web restructuring before their extinction, non-avian dinosaurs seem to have been characterized by largely stable and mostly static ecological niches during the Campanian and Maastrichtian, likely due to a large spectrum of already inhabited ecologies and morphotypes (25, 29, 55, 60, 61). However, niche stability might have placed dinosaur-dominated guilds at a disadvantage in the event of an abrupt shutdown of the trophic network, such as that experienced at the K/Pg boundary (1). …

The extinction of the dinosaurs and around three-quarters of all living species was almost certainly caused by a large asteroid impact 66 million years ago.Joanna V. Morgan 1 ✉, Timothy J. Bralower 2, Julia Brugger 3,4 and Kai Wünnemann 5,6 Abstract | The extinction of the dinosaurs and around three-quarters of all living species was almost certainly caused by a large asteroid impact 66 million years ago. Seismic data acquired across the impact site in Mexico have provided spectacular images of the approximately 200-kilometre-wide Chicxulub impact structure. In this Review, we show how studying the impact site at Chicxulub has advanced our understanding of formation of large craters and the environmental and palaeontological consequences of this impact. The Chicxulub crater’s asymmetric shape and size suggest an oblique impact and an impact energy of about 10 23 joules, …

The end-Cretaceous Chicxulub impact triggered Earth’s last mass-extinction, extinguishing ~ 75% of species diversity and facilitating a global ecological shift to mammal-dominated biomes. … Histological and histo-isotopic data from acipenseriform fishes at Tanis, independently supported by seasonally mediated animal behaviour, reveal that the Mesozoic came to an abrupt end in the paleo equivalent of late Spring or Summer in the northern hemisphere, aligned closely with spawning season (Fig. 4).Abstract The end-Cretaceous Chicxulub impact triggered Earth’s last mass-extinction, extinguishing ~ 75% of species diversity and facilitating a global ecological shift to mammal-dominated biomes. Temporal details of the impact event on a fine scale (hour-to-day), important to understanding the early trajectory of mass-extinction, have largely eluded previous studies. This study employs histological and histo-isotopic analyses of fossil fish that were coeval with a unique impact-triggered mass-death assemblage from the Cretaceous-Paleogene (KPg) boundary in North Dakota (USA). … ## Conclusions Histological and histo-isotopic data from acipenseriform fishes at Tanis, independently supported by seasonally mediated animal behaviour, reveal that the Mesozoic came to an abrupt end in the paleo equivalent of late Spring or Summer in the northern hemisphere, aligned closely with spawning season (Fig. 4). The initial devastating effects of the Chicxulub impact would have been amplified for biota in the northern hemisphere that possessed vulnerabilities inherent to this time span, which was a period of growth and reproduction for many animals and plants1,3,53. Mass mortality of young would have been especially disastrous for species that took many years to reach breeding age or bred only under ideal conditions. …

Over 75% of all species went extinct across the Cretaceous-Paleogene boundary (66 million years ago).… ## Key Points * Compared to sulfur and dust, soot emission from fires produces the largest reduction in surface light, temperature, and precipitation * A prolonged reduction in surface light from soot emission could help explain the marine extinction by starvation * High-latitude coastal regions experienced the least climatic, and likely biotic, disruption from the impact winter Plain Language Summary Over 75% of all species went extinct across the Cretaceous-Paleogene boundary (66 million years ago). This extinction coincided with a massive asteroid impact in the Yucatan Peninsula, which emitted material high into the atmosphere and potentially caused widespread fires. These emissions from the impactor, impact site, and fires would have blocked sunlight from reaching the surface, resulting in an “impact winter” that likely contributed to the mass extinction. However, details of the impact winter have been difficult to quantify. …

Sixty-six million years ago, an asteroid approximately 9 km in diameter hit the hydrocarbon- and sulfur-rich sedimentary rocks in what is now Mexico. … These events triggered a mass extinction, including dinosaurs, and led to the subsequent macroevolution of mammals.View saved research * 68k Accesses * 57 Citations * 759 Altmetric * Metrics details Abstract Sixty-six million years ago, an asteroid approximately 9 km in diameter hit the hydrocarbon- and sulfur-rich sedimentary rocks in what is now Mexico. Recent studies have shown that this impact at the Yucatan Peninsula heated the hydrocarbon and sulfur in these rocks, forming stratospheric soot and sulfate aerosols and causing extreme global cooling and drought. These events triggered a mass extinction, including dinosaurs, and led to the subsequent macroevolution of mammals. The amount of hydrocarbon and sulfur in rocks varies widely, depending on location, which suggests that cooling and extinction levels were dependent on impact site. Here we show that the probability of significant global cooling, mass extinction, and the subsequent appearance of mammals was quite low after an asteroid impact on the Earth’s surface. This significant event could have occurred if the asteroid hit the hydrocarbon-rich areas occupying approximately 13% of the Earth’s surface. …

This new timeline provides a precise interpolated absolute age for the K–Pg boundary of66.021±0.024/0.039/0.081Ma, constrains the ages of magnetic polarity Chrons C28 to C30, and offers a direct and independent test of early Paleogene astronomical and40Ar/39Ar based timescales. … Temporal calibration of paleontological and palynological data from the same deposits shows that the interval between the extinction of the dinosaurs and the appearance of earliest Cenozoic mammals in the Denver Basin lasted ∼185 ky (and no more than 570 ky) and the ‘fern spike’ lasted ∼1 ky (and no more than 71 ky) after the K–Pg boundary layer was deposited, indicating rapid rates of biotic extinction and initial recovery in the Denver Basin during this event.… We present a series of new high-precision uranium–lead (U–Pb) age determinations by the chemical abrasion isotope dilution thermal ionization mass spectrometry (CA-ID-TIMS) method from volcanic ash deposits within a tightly constrained magnetobiostratigraphic framework across the K–Pg boundary in the Denver Basin, Colorado, USA. This new timeline provides a precise interpolated absolute age for the K–Pg boundary of66.021±0.024/0.039/0.081Ma, constrains the ages of magnetic polarity Chrons C28 to C30, and offers a direct and independent test of early Paleogene astronomical and40Ar/39Ar based timescales. Temporal calibration of paleontological and palynological data from the same deposits shows that the interval between the extinction of the dinosaurs and the appearance of earliest Cenozoic mammals in the Denver Basin lasted ∼185 ky (and no more than 570 ky) and the ‘fern spike’ lasted ∼1 ky (and no more than 71 ky) after the K–Pg boundary layer was deposited, indicating rapid rates of biotic extinction and initial recovery in the Denver Basin during this event. Introduction The geological timescale provides the framework for interpreting Earth history. Major subdivisions of the timescale correspond to mass extinctions such as the K–Pg boundary, one of the two largest extinctions in earth history (e.g. Schulte et al., 2010). Calibration of the timescale in absolute time is critical for examining rates of geological and biological processes. …

Associated with a major extinction horizon (dinosaurs, ammonites, foraminifers, etc.) … However, U-Pb ages are reported to be slightly older than 66 MaCorrelation Events: Iridium geochemical anomaly. Associated with a major extinction horizon (dinosaurs, ammonites, foraminifers, etc.) Notes on Derivation of Age: Ar-Ar age suite. However, U-Pb ages are reported to be slightly older than 66 Ma References:

the Cretaceous-Paleogene (K-Pg) mass extinction represents the most well known and recent (ca. 66 million years ago)… Lofgren, D.L. The Bug Creek problem and the Cretaceous-Tertiary transition at McGuire Creek, Montana: CIP galley (K-T transition) DeMar, D.G. Late Cretaceous and Paleocene Lissamphibia and Squamata of Montana and the end-Cretaceous mass extinction, 2015: abstr. (the Cretaceous-Paleogene (K-Pg) mass extinction (ca. 66 million years ago); the K-Pg boundary) p. 2 (Of the "big five" mass extinctions recorded in Earth's history, the Cretaceous-Paleogene (K-Pg) mass extinction represents the most well known and recent (ca. 66 million years ago); the K-Pg mass extinction; the K-Pg boundary) p. 10 (Cretaceous-Paleogene boundary) Encyclopædia Britannica website, Dec. 16, 2016: K-T extinction (K-T extinction, abbreviation of Cretaceous-Tertiary extinction, also called K--Pg extinction or Cretaceous-Paleogene extinction, a global 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) …

The Chicxulub impact is widely regarded as the primary driver for the Cretaceous-Paleogene (KPg) mass extinction1,2, 3 and launched multiple long-term, planet-wide impacts for life on Earth. … The massive water surge, possibly originating from the nearby WIS, entombed the remains of autochthonous freshwater fish, turtles, reptiles, dinosaurs, and plants, mixed with allochthonous marine organisms including fish, ammonites, dinoflagellates, foraminifera, and marine reptiles, all intimately associated with impact ejecta emplaced via primary deposition.Introduction The Chicxulub impact is widely regarded as the primary driver for the Cretaceous-Paleogene (KPg) mass extinction1,2, 3 and launched multiple long-term, planet-wide impacts for life on Earth. A globally distributed Iridium-rich clay at the KPg boundary, constituting the re-accretion of impact fallout, was one of the first indicators of a massive extra-terrestrial impact 1. … The Tanis site possesses a highly constrained sedimentological chronology that is uniquely suited to examine the immediate post-impact events in a highly refined time-scale 7. The Tanis Event-deposit preceded the iridium-rich dust-sized fallout and was emplaced exclusively within the period of coarse ejecta accretion, which began in the study region ~ 13 min after impact and lasted for ~ 1 to 2 hours 7. The massive water surge, possibly originating from the nearby WIS, entombed the remains of autochthonous freshwater fish, turtles, reptiles, dinosaurs, and plants, mixed with allochthonous marine organisms including fish, ammonites, dinoflagellates, foraminifera, and marine reptiles, all intimately associated with impact ejecta emplaced via primary deposition. The sediment package is capped and temporally constrained by an iridium-rich clay layer (tonstein) that typifies the KPg boundary in the Western Interior [SUP MAT 2]. Tanis is characterized by a condensed synchronous thanatocoenosis (death-assemblage) that is thus far the only known preserved grouping of Chicxulub ejecta and articulated macro-organisms that died at the KPg boundary 7. …

This earlier extinction is occurs approximately 200 ka prior (66.2 Ma) to the K-Pg boundary, based on assumptions of depositional rate from magnetostratigraphy 17.… However, without a clear and unique sedimentological indication of facies change over the last 100 meters of the Cretaceous, a true biological event, rather than stratigraphic control, is better supported by the paleobiological evidence. This result supports the conclusions of previous work 17 and those that have relied on it 21 that there are two separate extinction events, one prior to the K-Pg boundary, and one simultaneous with the bolide impact at the K-Pg boundary. This earlier extinction is occurs approximately 200 ka prior (66.2 Ma) to the K-Pg boundary, based on assumptions of depositional rate from magnetostratigraphy 17. Work here presents yet more evidence that detailed studies of extinction rely heavily on carefully constructed sedimentological and paleobiological records, and that is impossible to divorce the fossil data from their geologic context. Methods

Sixty-six million years ago, an immense asteroid smacked into what is now the Yucatán Peninsula of Mexico, triggering global devastation and the world’s fifth mass extinction. The non-avian dinosaurs, pterosaurs and coil-shelled squid cousins called ammonites disappeared completely. … Ultimately Tanis will be another part of a much broader story. The extinction at the end of the Cretaceous was a global event that played out over the course of days, weeks, months and years. Despite the fact that the site has been heralded as recording “the day the dinosaurs died,” there’s no way to know when the very last non-avian dinosaur went extinct. The last terrible lizard likely fell long after the events recorded at Tanis, likely in another part of the world.A partially exposed, 65-million-year-old fish from the Tanis deposit in North Dakota. Robert DePalma / University of Kansas It may be considered one of the worst days in the history of life on Earth. Sixty-six million years ago, an immense asteroid smacked into what is now the Yucatán Peninsula of Mexico, triggering global devastation and the world’s fifth mass extinction. The non-avian dinosaurs, pterosaurs and coil-shelled squid cousins called ammonites disappeared completely. Even groups that survived, like mammals and lizards, suffered dramatic die-offs in the aftermath. Who perished, and who survived, set the stage for the next 66 million years—including our own origin 300,000 years ago. The Chicxulub impact was a catastrophic transition into a new world. … Witts hopes that the paper will help spur further discussion and analysis of other K/Pg sites around the globe. While geology is often thought of in terms of slow, gradual change, sometimes rapid transformation occurs. “I think Tanis reminds us geologists that sometimes it looks like the depositional stars align, and remarkable events could leave a signature preserved in the rock and fossil record,” he says. Ultimately Tanis will be another part of a much broader story. The extinction at the end of the Cretaceous was a global event that played out over the course of days, weeks, months and years. Despite the fact that the site has been heralded as recording “the day the dinosaurs died,” there’s no way to know when the very last non-avian dinosaur went extinct. The last terrible lizard likely fell long after the events recorded at Tanis, likely in another part of the world. DePalma says there is more to come from the Tanis site, and the mismatch between the claims made in the New Yorker article and the PNAS paper comes down to “triage” of what papers get priority. “We are already working on multiple follow-up papers and will be fully examining and reporting on everything found thus far,” he says.

The Cretaceous-Paleogene boundary ~65.5 million years ago marks one of the three largest mass extinctions in the past 500 million years. … A number of major animal groups disappeared across the boundary (e.g., the nonavian dinosaurs, marine and flying reptiles, ammonites, and rudists) (48) … The correlation between impact-derived ejecta and paleontologically defined extinctions at multiple locations around the globe leads us to conclude that the Chicxulub impact triggered the mass extinction that marks the boundary between the Mesozoic and Cenozoic eras ~65.5 million years ago.… Morgan,9 Clive R. Neal,22 Douglas J. Nichols,15 Richard D. Norris,23 Elisabetta Pierazzo,24 Greg Ravizza,25 Mario Rebolledo-Vieyra,26 Wolf Uwe Reimold,16 Eric Robin,27 Tobias Salge,28 Robert P. Speijer,29 Arthur R. Sweet,30 Jaime Urrutia-Fucugauchi,31 Vivi Vajda,32 Michael T. Whalen,33 Pi S. Willumsen32 The Cretaceous-Paleogene boundary ~65.5 million years ago marks one of the three largest mass extinctions in the past 500 million years. The extinction event coincided with a large asteroid impact at Chicxulub, Mexico, and occurred within the time of Deccan flood basalt volcanism in India. Here, we synthesize records of the global stratigraphy across this boundary to assess the proposed causes of the mass extinction. … What Does the Fossil Record Reveal About the Global Consequences for Life? The scale of biological turnover between the Cre taceous and Paleogene is nearly unprecedented in Earth history (1). A number of major animal groups disappeared across the boundary (e.g., the nonavian dinosaurs, marine and flying reptiles, ammonites, and rudists) (48), and several other major groups suffered considerable, but not complete, species level extinction (e.g., planktic foraminifera, calcar eous nannofossils, land plants) (12, 13, 37, 49). Even the groups that showed negligible extinc tions exhibited substantial changes in assemblage composition (e.g., benthic foraminifera) (50). … What Do We Need to Look at Next? The correlation between impact-derived ejecta and paleontologically defined extinctions at multiple locations around the globe leads us to conclude that the Chicxulub impact triggered the mass extinction that marks the boundary between the Mesozoic and Cenozoic eras ~65.5 million years ago. This conclusion is reinforced by the agreement of ecological extinction patterns with modeled environmental perturbations. …

Sixty-six million years ago, life on Earth was paid a visit by a very unwelcome guest: the Chicxulub impactor, an asteroid that infamously wiped out all non-avian dinosaurs. … Brusatte and his colleagues dated the layer to between 66.4 and 66 million years ago. … "These were the dinosaurs that were greeted by the asteroid," Brusatte explains in a statement. "And when we compare them with the only other fossils accurately dated from this time, from further north, we can see they are much different. There clearly were many types of dinosaurs thriving up until that moment the asteroid ended it all."Two T. rex dinosaurs square up for a fight in an illustration. Dinosaurs in the Cretaceous were thriving until the Chicxulub asteroid initiated a mass extinction. Mark Garlick / Science Photo Library via Getty Images Sixty-six million years ago, life on Earth was paid a visit by a very unwelcome guest: the Chicxulub impactor, an asteroid that infamously wiped out all non-avian dinosaurs. The state of dinosaurs before this unfortunate end, however, is a subject of fierce debate in the scientific community. Did dinosaurs thrive until their very last moments? Or had their diversity already plummeted, creating a weak population already vulnerable to extinction? … “There is no sign that these dinosaurs were in any trouble, or that anything unusual was happening to them, or that they were in any type of long-term decline,” Steve Brusatte, a vertebrate paleontologist at the University of Edinburgh and co-author of the study, tells the Guardian’s Nicola Davis. Simply put, Brusatte and his colleagues dated the layer to between 66.4 and 66 million years ago. That means its dinosaurs lived at the same time as those preserved in the Hell Creek Formation, a famous paleontological site in North Dakota and Montana and home to many of the fossils that have already shed light on this period. … This approach revealed that the rocks—and, indirectly, the fossils within them—formed in the last 380,000 years of the Cretaceous Period, which was ended by the Chicxulub impact. The researchers confirmed that age with the second dating method: a geochemical analysis of crystals in sandstones in those same rocks. “These were the dinosaurs that were greeted by the asteroid,” Brusatte explains in a statement. “And when we compare them with the only other fossils accurately dated from this time, from further north, we can see they are much different. There clearly were many types of dinosaurs thriving up until that moment the asteroid ended it all.” The research doesn’t necessarily mean all dinosaurs thrived before the asteroid, and the authors write that the current picture “is a North American one.”

The entire reason paleontologists make that split is because of a catastrophe that struck 66 million years ago. An asteroid more than 6 miles across struck what’s now the Yucatan Peninsula, triggering the fifth mass extinction in the world’s history. … All told, more than 75 percent of species known from the end of the Cretaceous period, 66 million years ago, didn’t make it to the following Paleogene period. The geologic break between the two is called the K-Pg boundary, and beaked birds were the only dinosaurs to survive the disaster.… About 150 million years ago, in the Jurassic, the first birds evolved from small, feathery, raptor-like dinosaurs, becoming another branch on the dinosaur family tree. For more than 80 million years, birds of all sorts flourished, from loon-like swimmers with teeth to beaked birds that carried streamer-like feathers as they flew. With hindsight, birds can be categorized as avian dinosaurs and all the other sorts—from Stegosaurus to Brontosaurus—are non-avian dinosaurs. The entire reason paleontologists make that split is because of a catastrophe that struck 66 million years ago. An asteroid more than 6 miles across struck what’s now the Yucatan Peninsula, triggering the fifth mass extinction in the world’s history. Some of the debris thrown into the atmosphere returned to Earth, the friction turning the air into an oven and sparking forest fires as it landed all over the world. Then the intensity of the heat pulse gave way to a prolonged impact winter, the sky blotted out by soot and ash as temperatures fell. All told, more than 75 percent of species known from the end of the Cretaceous period, 66 million years ago, didn’t make it to the following Paleogene period. The geologic break between the two is called the K-Pg boundary, and beaked birds were the only dinosaurs to survive the disaster. “There has been a lot of discussion about what enabled modern-type birds to survive the K-Pg extinction while other birds groups, non-avian dinosaurs, and even pterosaurs perished,” says Royal BC Museum paleontologist Derek Larson. The end of the Cretaceous boasted an entire array of birds and bird-like reptiles. But of these groups, it was only the beaked birds that survived. …

According to a paper by Renne's team in the April 25 issue of Science, the best date for the Cretaceous-Tertiary, or K/T, boundary is now 65.95 million years, give or take 40,000 years.… As a result, argon-argon dating today can provide more precise absolute dates for many geologic events, ranging from volcanic eruptions and earthquakes to the extinction of the dinosaurs and many other creatures at the end of the Cretaceous period and the beginning of the Tertiary period. That boundary had previously been dated at 65.5 million years ago, give or take 300,000 years. According to a paper by Renne's team in the April 25 issue of Science, the best date for the Cretaceous-Tertiary, or K/T, boundary is now 65.95 million years, give or take 40,000 years. "The importance of the argon-argon technique is that it is the only technique that has the dynamic range to cover nearly all of Earth's history," Renne said. "What this refinement means is that you can use different chronometers now and get the same answer, whereas, that wasn't true before."

Dinosaurs went extinct about 65 million years ago (at the end of the Cretaceous Period), after living on Earth for about 165 million years.When did dinosaurs become extinct? 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. (Using this same time scale, the Earth would have formed approximately 18.5 years earlier.) Using the same scale, people (Homo sapiens) have been on earth only since December 31 (New Year's eve). …

70 · 30 31 32 · C30 C31 C32 · MAASTRICHTIAN · 66.0 72.1GEOLOGIC TIME SCALE v. 6.0 MESOZOIC AGE (Ma) · MAGNETIC T IS H · POLARITY . M O N A · . N O PERIOD R H C · EPOCH · AGE · PICKS (Ma) 70 · 30 31 32 · C30 C31 C32 · MAASTRICHTIAN · 66.0 72.1 33 · C33 · CAMPANIAN 80 · S · LATE U · SANTONIAN · 83.6 CONIACIAN · 86.3 90 · O · TURONIAN · 89.8 100 · 34 · E C34 · CENOMANIAN · 93.9 100.5 110 · C A T · ALBIAN 120 · M0r · E R · EARLY · APTIAN · ~113 130 · M1 M3 M5 · C · BARREMIAN · ~125 M10 · HAUTERIVIAN · ~129.4 ~132.6 M12 M14 · VALANGINIAN · ~139.8 140 · M16 · BERRIASIAN M18 M20 · ~145.0 · …

Danian Maastrichtian 72.1 ±0.2 Campanian… ic · o e · Miocene · Serravallian M o · N · Langhian z o n · Burdigalian L/E e C · Aquitanian Chattian Oligocene · Rupelian e · Priabonian n e · Bartonian ic · g · Eocene · Lutetian o z · o le o r · a · Ypresian e n · P a h · Thanetian P · Paleocene · Selandian Danian Maastrichtian 72.1 ±0.2 Campanian 83.6 ±0.2 Upper · Santonian · 86.3 ±0.5 Coniacian · 89.8 ±0.3 ic · s · Turonian u o o z · e · Cenomanian o s · c ta · Albian e M · e r C · Aptian Barremian Lower Hauterivian Valanginian Berriasian Tithonian …

Danian Maastrichtian 72.1 ±0.2 Campanian · 83.6 ±0.2… e g · Tortonian o e · Miocene · Serravallian ic · N · Langhian o z o · Burdigalian n · Aquitanian e C · Chattian Oligocene · Rupelian e · Priabonian n e · Bartonian ic · g · Eocene · Lutetian o z · o le o r · a · Ypresian e n · P a h · Thanetian P · Paleocene · Selandian Danian Maastrichtian 72.1 ±0.2 Campanian · 83.6 ±0.2 Upper · Santonian · 86.3 ±0.5 Coniacian · 89.8 ±0.3 ic · s · Turonian u o o z · e · Cenomanian o s · c ta · Albian e M · e r C · Aptian Lower · Barremian Hauterivian Valanginian Berriasian Tithonian Upper · Kimmeridgian · …

The Cretaceous-Paleogene (K–Pg) extinction event, also known as the K–T extinction, happened about 66 million years agoWhat was the K–T extinction? The Cretaceous-Paleogene (K–Pg) extinction event, also known as the K–T extinction, happened about 66 million years ago a

The Cretaceous–Paleogene (K–Pg) extinction event, formerly known as the Cretaceous-Tertiary (K–T) extinction event, was a major mass extinction of three-quarters of the plant and animal species on Earth which occurred approximately 66 million years ago. … Scientists agree that all non-avian dinosaurs became extinct at the K–Pg boundary.… - Complex Cretaceous–Paleogene clay layer (gray) in the Geulhemmergroeve tunnels near Geulhem, The Netherlands (finger is just below the actual Cretaceous–Paleogene boundary); - Wyoming rock with an intermediate claystone layer that contains 1,000 times more iridium than the upper and lower layers. Picture taken at the San Diego Natural History Museum; - Rajgad Fort's Citadel, an eroded hill from the Deccan Traps, which are another hypothesized cause of the K–Pg extinction event. The Cretaceous–Paleogene (K–Pg) extinction event, formerly known as the Cretaceous-Tertiary (K–T) extinction event, was a major mass extinction of three-quarters of the plant and animal species on Earth which occurred approximately 66 million years ago. The event caused the extinction of all of the non-avian dinosaurs and most other tetrapods weighing more than 25 kg (55 lb), with the exception of some ectothermic species such as sea turtles and crocodilians. It marked the end of the Cretaceous period, and with it the Mesozoic era, while heralding the beginning of the next and current geological era, the Cenozoic Era. … Tyrannosaurus was among the dinosaurs living on Earth before the extinction. Scientists agree that all non-avian dinosaurs became extinct at the K–Pg boundary. There is no evidence that late Maastrichtian non-avian dinosaurs could burrow, swim, or dive, which suggests they were unable to shelter themselves from the worst parts of any environmental stress that occurred at the K–Pg boundary. It is possible that small dinosaurs (other than birds) did survive, but they would have been deprived of food, as herbivorous dinosaurs would have found plant material scarce and carnivores would have quickly found prey in short supply.

The Cretaceous–Paleogene (K–Pg) extinction event, [a] formerly known as the Cretaceous–Tertiary (K–T) extinction event, [b] was a major mass extinction of three-quarters (75%) of the plant and animal species on Earth [2] [3] [4] which occurred around 66 million years ago. … Scientists agree that all non-avian dinosaurs became extinct at the K–Pg boundary.… - Complex Cretaceous–Paleogene clay layer (gray) in the Geulhemmergroeve tunnels near Geulhem, The Netherlands (finger is just below the actual Cretaceous–Paleogene boundary); - Wyoming rock with an intermediate claystone layer that contains 1,000 times more iridium than the upper and lower layers. Picture taken at the San Diego Natural History Museum; - Rajgad Fort's Citadel, an eroded hill from the Deccan Traps, which are another hypothesized cause of the K–Pg extinction event. The Cretaceous–Paleogene (K–Pg) extinction event, [a] formerly known as the Cretaceous–Tertiary (K–T) extinction event, [b] was a major mass extinction of three-quarters (75%) of the plant and animal species on Earth [2] [3] [4] which occurred around 66 million years ago. The event caused the extinction of all the non-avian dinosaurs and most other tetrapods weighing more than 25 kg (55 lb), excepting some ectothermic species such as sea turtles and crocodilians. [5] It marked the ends of both the Cretaceous period and the Mesozoic era, and logged the beginning of the current geological era, the Cenozoic era. … Tyrannosaurus was among the dinosaurs living on Earth before the extinction Scientists agree that all non-avian dinosaurs became extinct at the K–Pg boundary. There is no evidence that late Maastrichtian non-avian dinosaurs could burrow, swim, or dive, which suggests they were unable to shelter themselves from the worst parts of any environmental stress that occurred at the K–Pg boundary. It is possible that small dinosaurs (other than birds) did survive, but they would have been deprived of food, as herbivorous dinosaurs would have found plant material scarce and carnivores would have quickly found prey in short supply. [93]

Prior to 2013, it was commonly cited as having happened about 65 million years ago, but Renne and colleagues (2013) gave an updated value of 66 million years. … Paul Renne of the Berkeley Geochronology Center has reported that the date of the asteroid event is 66,038,000 years ago, plus or minus 11,000 years, based on Ar-Ar dating.Asteroid impact hypothesis Luis Walter Alvarez, left, and his son Walter, right, at the K–T boundary in Gubbio, Italy, 1981 The **Alvarez hypothesis** posits that the mass extinction of the non-avian dinosaurs and many other living things during the Cretaceous–Paleogene extinction event was caused by the impact of a large asteroid on the Earth. Prior to 2013, it was commonly cited as having happened about 65 million years ago, but Renne and colleagues (2013) gave an updated value of 66 million years. Evidence indicates that the asteroid fell in the Yucatán Peninsula, at Chicxulub, Mexico. The hypothesis is named after the father-and-son team of scientists Luis and Walter Alvarez, who first suggested it in 1980. Shortly afterwards, and independently, the same was suggested by Dutch paleontologist Jan Smit. In March 2010, an international panel of scientists endorsed the asteroid hypothesis, specifically the Chicxulub impact, as being the cause of the extinction. … There were other earlier speculations on the possibility of an impact event, but without strong confirming evidence. Evidence and projects Badlands near Drumheller, Alberta where erosion has exposed the K–Pg boundary. The location of the impact was unknown when the Alvarez team developed their hypothesis, but later scientists discovered the Chicxulub Crater in the Yucatán Peninsula, now considered the likely impact site. Paul Renne of the Berkeley Geochronology Center has reported that the date of the asteroid event is 66,038,000 years ago, plus or minus 11,000 years, based on Ar-Ar dating. He further posits that the mass extinction of dinosaurs occurred within 33,000 years of this date. In April 2019, a paper was published in PNAS which describes evidence from a fossil site in North Dakota that the authors say provides a "postimpact snapshot" of events after the asteroid collision "including ejecta accretion and faunal mass death". …

Maastrichtian 66.04Early Maastrichtian 66.04 Campanian

Around 66 million years ago, the Cretaceous-Paleogene (K-Pg) extinction marked the end of the Mesozoic Era. While this event is most famously known for wiping out the non-avian dinosaurs, many other organisms were affected—including plants.Dinosaur & Plant Extinctions Around 66 million years ago, the Cretaceous-Paleogene (K-Pg) extinction marked the end of the Mesozoic Era. While this event is most famously known for wiping out the non-avian dinosaurs, many other organisms were affected—including plants. Extinction patterns in plants, however, differed from those in dinosaurs. High-level groupings of dinosaurs went extinct, leaving only the avian dinosaurs. In plants, extinction primarily occurred at the species level; many high-level groupings (for example, orders and families) survived. As primary producers, plants are fundamental to ecosystems. Loss of plant life at any taxonomic level can have devastating impacts on the organisms that rely on them.

The Cretaceous/Paleogene (K/Pg) boundary is marked by one of the largest mass extinctions in Earth's historyAbstract The Cretaceous/Paleogene (K/Pg) boundary is marked by one of the largest mass extinctions in Earth’s history, with geological evidence for this event being expressed in hundreds of locations worldwide. An extensively studied section located near El Kef, northwestern Tunisia, is characterized by the classic iridium-rich K/Pg boundary layer, abundant and well-preserved microfossils, and apparently continuous sedimentation throughout the early Danian with no previously described structural complication. …

We further present new geochronologic data for the Cretaceous-Paleogene boundary that provide the most precise date yet, of 66.052 ± 0.008/0.043 Ma.… Here, we show results for 14 new magnetostratigraphic sections, and 18 new high-precision 40Ar/39Ar dates, which together provide six independent constraints on the age of the C29r/C29n reversal and two constraints on the C30n/ C29r reversal. Together, these results show that the duration of C29r was 587 ± 53 ka, consistent with the most recent Geologic Time Scale calibration and previous U-Pb age models. We further present new geochronologic data for the Cretaceous-Paleogene boundary that provide the most precise date yet, of 66.052 ± 0.008/0.043 Ma. Integration of our results into the extensive paleontological framework for this region further provides important constraints on rates of terrestrial faunal change across the Cretaceous-Paleogene boundary. Authors

It is now thought that the entire igneous emplacement took place in a relatively short geological interval (about one million years), and this volcanic activity occurred during the latest Maastrichtian and the early Danian. … In addition, recent detailed analysis of the Chicxulub crater has indicated a formation date of 66,038,000 million years ago (plus or minus 11,000 years as a margin of error). … It is a committee within the International Commission on Stratigraphy (ICS), that decides on the dates of geological boundaries, and during 2012/2013 revisions of the geological timeline took place including a change from the end of the Maastrichtian faunal stage from 65.5 mya (+/- 0.3 million years) to 66 mya.The Deccan Traps and the Chicxulub Crater Geochronologists, most notably Professor Vincent Courtillot, have redefined the extensive volcanic activity that led to the formation of the Deccan Traps in India. It is now thought that the entire igneous emplacement took place in a relatively short geological interval (about one million years), and this volcanic activity occurred during the latest Maastrichtian and the early Danian. The Danian is the first stage of the Palaeocene Epoch that marks the beginning of Palaeogene Period of the Cenozoic Era. In addition, recent detailed analysis of the Chicxulub crater has indicated a formation date of 66,038,000 million years ago (plus or minus 11,000 years as a margin of error). A geophysical map of the Chicxulub impact crater. Picture credit: NASA. The International Commission on Stratigraphy (ICS) It is a committee within the International Commission on Stratigraphy (ICS), that decides on the dates of geological boundaries, and during 2012/2013 revisions of the geological timeline took place including a change from the end of the Maastrichtian faunal stage from 65.5 mya (+/- 0.3 million years) to 66 mya. Geological boundaries are subject to change. The development of consistent, extremely accurate numerical dating techniques and the continued acquisition of new numerical ages will continue to lead to refinements of the geological timescale.