What Really Did Kill The Dinosaurs?

EnolaGaia

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... whilst amusing i also found it astonishing that 'only' 45 years ago, when this book was published, there is no mention of asteroid impact.
astonishing because this is such a common and well known FACT that its hard for me to get my head around the idea that within my lifetime this was an unknown. ...

Yep ... The seminal Alvarez et al. paper on the K-T boundary iridium layer was published in 1980. It wouldn't be until the late 1980s that scholarly opinion began to seriously shift toward acceptance of the impact hypothesis.
 

EnolaGaia

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The latest research report regarding the asteroid-versus-vulcanism debate claims the asteroid strike was the deciding factor in eliminating the dinosaurs ...
Asteroid vs. Volcanoes: New Modeling Shows What Made the Earth Uninhabitable for Dinosaurs

Modeling of the Chicxulub asteroid impact 66 million years ago shows it created a world largely unsuitable for dinosaurs to live in.

The asteroid, which struck the Earth off the coast of Mexico at the end of the Cretaceous era 66 million years ago, has long been believed to be the cause of the demise of all dinosaur species except those that became birds.

However, some researchers have suggested that tens of thousands of years of large volcanic eruptions may have been the actual cause of the extinction event, which also killed off almost 75% of life on Earth.

Now, a research team from Imperial College London, the University of Bristol and University College London has shown that only the asteroid impact could have created conditions that were unfavorable for dinosaurs across the globe. ...

They also show that the massive volcanism could also have helped life recover from the asteroid strike in the long term. Their results are published today in Proceedings of the National Academy of Sciences. ...

The asteroid strike would have released particles and gases high into the atmosphere, blocking out the Sun for years and causing permanent winters. Volcanic eruptions also produce particles and gases with Sun-blocking effects, and around the time of the mass extinction there were tens of thousands of years of eruptions at the Deccan Traps, in present-day India.

To determine which factor, the asteroid or the volcanism, had more climate-changing power, researchers have traditionally used geological markers of climate and powerful mathematical models. In the new paper, the team combined these methods with information about what kinds of environmental factors, such as rainfall and temperature, each species of dinosaur needed to thrive.

They were then able to map where these conditions would still exist in a world after either an asteroid strike or massive volcanism. They found that only the asteroid strike wiped out all potential dinosaur habitats, while volcanism left some viable regions around the equator. ...

FULL STORY: https://scitechdaily.com/asteroid-v...t-made-the-earth-uninhabitable-for-dinosaurs/
 

EnolaGaia

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Here are the bibliographic details and abstract for this latest published research article. The full report is accessible at the link below.

Asteroid impact, not volcanism, caused the end-Cretaceous dinosaur extinction
Alfio Alessandro Chiarenza, Alexander Farnsworth, Philip D. Mannion, Daniel J. Lunt, Paul J. Valdes, Joanna V. Morgan, and Peter A. Allison
PNAS first published June 29, 2020
https://doi.org/10.1073/pnas.2006087117

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. Conversely, long-term forcing from Deccan volcanism (carbon dioxide [CO2]-induced warming) leads to increased habitat suitability. Short-term (aerosol cooling) volcanism still allows equatorial habitability. These results support the asteroid impact as the main driver of the non-avian dinosaur extinction. By contrast, induced warming from volcanism mitigated the most extreme effects of asteroid impact, potentially reducing the extinction severity.

FULL REPORT: https://www.pnas.org/content/early/2020/06/23/2006087117
 

EnolaGaia

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The asteroid did it ...

Scientists analyzing geochemical composition of the Chicxulub crater drilling cores have concluded the residual dust from the crater's impact origin is asteroidal. They have declared 'case closed' on the cause (or at least primary proximate cause) of the dinosaurs' extinction at the K-Pg boundary.
Asteroid Dust Found in Crater Closes Case on What Killed the Dinosaurs

Researchers believe they have closed the case of what killed the dinosaurs, definitively linking their extinction with an asteroid that slammed into Earth 66 million years ago by finding a key piece of evidence: asteroid dust inside the impact crater.

Death by asteroid rather than by a series of volcanic eruptions or some other global calamity has been the leading hypothesis since the 1980s, when scientists found asteroid dust in the geologic layer that marks the extinction of the dinosaurs. This discovery painted an apocalyptic picture of dust from the vaporized asteroid and rocks from impact circling the planet, blocking out the sun and bringing about mass death through a dark, sustained global winter — all before drifting back to Earth to form the layer enriched in asteroid material that’s visible today. ...

In the 1990s, the connection was strengthened with the discovery of a 125-mile-wide Chicxulub impact crater beneath the Gulf of Mexico that is the same age as the rock layer. The new study seals the deal, researchers said, by finding asteroid dust with a matching chemical fingerprint within that crater at the precise geological location that marks the time of the extinction.

“The circle is now finally complete,” said Steven Goderis, a geochemistry professor at the Vrije Universiteit Brussel, who led the study published in Science Advances on February 24, 2021. ...

“We are now at the level of coincidence that geologically doesn’t happen without causation,” said co-author Sean Gulick ... “It puts to bed any doubts that the iridium anomaly [in the geologic layer] is not related to the Chicxulub crater.” ...

FULL STORY: https://scitechdaily.com/asteroid-dust-found-in-crater-closes-case-on-what-killed-the-dinosaurs/
 

EnolaGaia

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Here are the bibliographic details and abstract from the published research. The full research article is accessible at the link below.

Globally distributed iridium layer preserved within the Chicxulub impact structure
BY Steven Goderis, Honami Sato, Ludovic Ferrière, Birger Schmitz, David Burney, Pim Kaskes, et al.
Science Advances, 24 FEB 2021 : EABE3647
https://doi.org/10.1126/sciadv.abe3647

Abstract
The Cretaceous-Paleogene (K-Pg) mass extinction is marked globally by elevated concentrations of iridium, emplaced by a hypervelocity impact event 66 million years ago. Here, we report new data from four independent laboratories that reveal a positive iridium anomaly within the peak-ring sequence of the Chicxulub impact structure, in drill core recovered by IODP-ICDP Expedition 364. The highest concentration of ultrafine meteoritic matter occurs in the post-impact sediments that cover the crater peak ring, just below the lowermost Danian pelagic limestone. Within years to decades after the impact event, this part of the Chicxulub impact basin returned to a relatively low-energy depositional environment, recording in unprecedented detail the recovery of life during the succeeding millennia. The iridium layer provides a key temporal horizon precisely linking Chicxulub to K-Pg boundary sections worldwide.

SOURCE: https://advances.sciencemag.org/content/7/9/eabe3647
 

Nosmo King

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Here are the bibliographic details and abstract from the published research. The full research article is accessible at the link below.

Globally distributed iridium layer preserved within the Chicxulub impact structure
BY Steven Goderis, Honami Sato, Ludovic Ferrière, Birger Schmitz, David Burney, Pim Kaskes, et al.
Science Advances, 24 FEB 2021 : EABE3647
https://doi.org/10.1126/sciadv.abe3647

Abstract
The Cretaceous-Paleogene (K-Pg) mass extinction is marked globally by elevated concentrations of iridium, emplaced by a hypervelocity impact event 66 million years ago. Here, we report new data from four independent laboratories that reveal a positive iridium anomaly within the peak-ring sequence of the Chicxulub impact structure, in drill core recovered by IODP-ICDP Expedition 364. The highest concentration of ultrafine meteoritic matter occurs in the post-impact sediments that cover the crater peak ring, just below the lowermost Danian pelagic limestone. Within years to decades after the impact event, this part of the Chicxulub impact basin returned to a relatively low-energy depositional environment, recording in unprecedented detail the recovery of life during the succeeding millennia. The iridium layer provides a key temporal horizon precisely linking Chicxulub to K-Pg boundary sections worldwide.

SOURCE: https://advances.sciencemag.org/content/7/9/eabe3647
Surely if birds are decended from raptor type dinosaurs, they never went completely extinct and as previously mentioned, other creatures such as crocodiles and sharks decended from prehistoric versions, along with insects such as dragonflys, so how did these survive where others didnt, i was always under the impression that the nuclear winter type result of asteriod crater debris and /or volcanoes, caused the larger herbivourous sauropods died off due to loss of food followed by the carnivours that preyed on them, or that could be a mandela effect lol
 

EnolaGaia

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New dating results seem to rule out the Boltysh impactor / crater (Ukraine) as the blow that killed the dinosaurs.
New Research of Impact Crater Blows Away Previous Estimates on Its Age

If you travel 140 miles southeast of Kiev, Ukraine, just before you reach the tiny village of Bukvarka, you’ll arrive at a patch of forest that streaks across agricultural lands. ...

Scientists say that about 65 million years ago an asteroid the length of three Eiffel Towers struck here, its fiery fallout blanketing an area the size of present-day Vermont. The impact dumped a colossal amount of heat into the ground—enough to melt rock and form a massive depression called the Boltysh crater, a hole now filled in by asteroid detritus and sediments of a lake long gone. ...

Previous studies have assigned the Boltysh impact event a broad range of dates to suggest that it may have coincided with the Chicxulub impact event—with the two asteroid strikes both contributing to the extinction of the dinosaurs. Now, a more precise follow-up study published today in Science Advances suggests the Boltysh impact occurred 650,000 years later than the Chicxulub impact, long after the dinosaurs disappeared. Though the Boltysh impact is no longer fingered in the famous mass extinction event, pinpointing the crater’s age has allowed scientists to correlate the asteroid strike to other global shake-ups of its time. ...

Annemarie Pickersgill, a geologist at the University of Glasgow, ... dated the Boltysh crater by looking at the age of the sediments that had settled on top. ... Her team examined the cores drilled from this sedimentary pileup using a dating method that measures the accumulation a particular isotope of argon and estimated the crater’s age to be 65.39 million years. ...

The first attempts to date the Boltysh crater in the early 2000s involved the same dating method, albeit with lower precision due to technological limitations. Scientists estimated the impact occurred sometime during a span of 1.3 million years. The imprecise measurement left open the possibility that the Boltysh impact may have overlapped with Chicxulub’s fateful formation. This wide age range fertilized speculations that the Boltysh impactor, beating Chicxulub’s to Earth by a hair, acted as the first of a one-two punch that wiped out the dinosaurs. ... Pickersgill’s team could increase the measurement precision fourfold ... Their results confirm that the Boltysh has nothing to do with the extinction of the dinosaurs, because it happened much later. ...

The Boltysh impact may no longer be guilty of helping to cause the extinction of dinosaurs, but its new, more precise age puts it around a time of much climatic upheaval. ...
FULL STORY: https://www.smithsonianmag.com/scie...ws-away-previous-estimates-its-age-180978023/
 

EnolaGaia

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Newly published survey research suggests large non-avian dinosaurs were already facing increasing extinction risks for about 10 million years before the Chicxulub impact.
Large Dinosaurs Were Prone to Extinction Way Before The Asteroid, New Study Argues

While evidence for ... end-Cretaceous impact is indisputable, debate within the paleontological community has been ongoing as to whether dinosaur extinction was abrupt or gradual.

The extinctions do coincide with a period of long-term environmental upheaval, largely the result of the continued breaking up of the supercontinents Laurasia and Gondwana. High sea levels, cooling climates, the spread of new habitat on land, as well as massive volcanic activity, may have all played significant roles in the mass extinction event.

Up until now, analysis of fossil data has yielded no convincing evidence of a decline in dinosaur species before their extinction. A phylogenetic study in 2016, which used dinosaur timetrees, challenged the idea of a sudden extinction, but this conclusion proved to be contentious.

The fossil record is a notoriously difficult source of evidence, with critiques of that study pointing to gaps in the dinosaur fossil record and sampling biases which could have led to the under-reporting of certain Cretaceous dinosaur species.

Now, a new study has lent additional evidence to the hypothesis that non-avian dinosaurs were already teetering on the edge of extinction before the cataclysmic events of the infamous asteroid impact. ...
FULL STORY: https://www.sciencealert.com/non-av...-decline-before-extinction-asteroid-hit-earth
 

EnolaGaia

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Here are the bibliographic details and abstract of the published study. The full article is accessible at the link below.


Condamine, F.L., Guinot, G., Benton, M.J. et al.
Dinosaur biodiversity declined well before the asteroid impact, influenced by ecological and environmental pressures.
Nat Commun 12, 3833 (2021).
https://doi.org/10.1038/s41467-021-23754-0

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. These results support an environmentally driven decline of non-avian dinosaurs well before the asteroid impact.

FULL ARTICLE: https://www.nature.com/articles/s41467-021-23754-0
 

EnolaGaia

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Newly published research is claimed to pinpoint the season when the asteroid ended the dinosaurs. It was springtime ...
Dinosaurs’ Last Spring: Groundbreaking Study Pinpoints Timing of Chicxulub Asteroid Impact

A groundbreaking study led by researchers at Florida Atlantic University and an international team of scientists conclusively confirms the time year of the catastrophic Chicxulub asteroid, responsible for the extinction of dinosaurs and 75 percent of life on Earth 66 million years ago. Springtime, the season of new beginnings, ended the 165-million-year reign of dinosaurs and changed the course of evolution on Earth. ...
FULL STORY: https://scitechdaily.com/dinosaurs-...inpoints-timing-of-chicxulub-asteroid-impact/
 

Ronnie Jersey

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Apparently the Earth goes through cyles of heating and cooling, and Ice Ages, about every 10,000 years or so -
Killing off much of whatever life is present at the time, while some survives.
The north and south ice caps melt, the condensation rises up into the atmosphere, affecting the entire planet.
Then after heating up for some time, suddenly the cool down starts up again and the ice caps return, along with different life forms.
JMO this is the reason for archaeologists finding strange evidence that they can't account for - such as human footprints alongside dinosaur tracks, and advanced items from civilizations thought of as primitive. Life comes and goes and springs up eternally.
And currently we are in the warm-up trend, none of us will be alive to deal with another Ice Age, which probably killed off the dinosaurs.
JMO.
 
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Analogue Boy

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I’ll tell you what killed the dinosaurs.
Fucking boredom. They just got totally fed up doing the same thing for about 150 million years.
 

RaM

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Na they died of hyperthermia, they could not afford to put the heating on due to green taxes.
:omr:
 

EnolaGaia

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Analysis of sedimentary strata that were underwater at the time of the Chicxulub impact indicates the amount of sulfur thrown into the atmosphere - and the subsequent global cooling it caused - were significantly greater than previously believed.

Sulfur from dino-killing asteroid caused way more global cooling than thought

When the dinosaur-destroying asteroid collided with Earth 66 million years ago, massive amounts of sulfur — volumes more than were previously thought — were thrown high above land into the stratosphere, a new study finds.

Once airborne, this vast cloud of sulfur-bearing gases blocked the sun and cooled Earth for decades to centuries, then fell down as lethal acid rain on Earth, changing the chemistry of the oceans for tens of thousands of years, which is longer than previously thought, the study found.

The findings show that "we've underestimated the amount of this sulfur that this asteroid impact created," study co-researcher James Witts, a lecturer in the School of Earth Sciences at the University of Bristol in the U.K., told Live Science. As a result, "the climate change that was associated with it was much greater perhaps than we thought previously."

The fact that sulfur continued pouring down on Earth's surface for so long may help explain why it took so long for life, especially marine life, to recover, as some of the sulfur that fell onto the land would have then washed away into the oceans, Witts said. ...

The study was published online Monday (March 21) in the journal Proceedings of the National Academy of Sciences.
FULL STORY: https://www.livescience.com/sulfur-dinosaur-killing-asteroid-impact

PUBLISHED REPORT: https://www.pnas.org/doi/full/10.1073/pnas.2119194119
 

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EnolaGaia

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This is really interesting ... A newly discovered crater off the coast of West Africa has been dated to the same period as the Chicxulub crater off Yucatan. This raises the possibility the dinosaur-killing impact event involved more than one asteroidal impactor.
Did the asteroid that wiped out the dinosaurs have a sibling? Crater in West Africa hints maybe.

A likely asteroid impact crater from the latter days of the dinosaurs has been discovered off the coast of West Africa, raising questions about whether the asteroid that wiped out the dinos may have had a smaller sibling that struck around the same time.

The crater, hidden under about 3,000 feet (900 meters) of water and 1,300 feet (400 m) of sediment, hasn't been directly studied yet; it's only been detected in reconstructions of the ocean bed made using seismic waves. To prove beyond a shadow of a doubt that the crater is indeed from an asteroid, scientists will need to drill into the structure and find minerals shocked by extreme heat and pressure. But the crater's shape does point to an extraterrestrial origin, said David Kring, principal scientist at the Lunar and Planetary Institute who was not involved in the current study but was one of the discoverers of the Chicxulub impact site, the crater left by the asteroid that killed the nonavian dinosaurs about 66 million years ago.

"I have to congratulate the team for finding what looks like a probable impact crater," Kring told Live Science. "That's very important, because we have so few impact craters preserved on the Earth. Every single one that we can find provides a new window, new insights into the geological processes that shape them and their effects on biological evolution of Earth."

The new crater was formed very close in time to the Chicxulub impact, raising the possibility that the two may be related. ...

When Uisdean Nicholson, a geologist at Heriot Watt University in the U.K., and his team started poring through seismic data from the West Coast of Africa, they weren't looking for signs of space rocks. ...

To the researchers' surprise, on the seafloor about 250 miles (400 kilometers) from the coast of Guinea and Guinea -Bissau, they found evidence of an odd divot in the rock layers.

"The crater is very striking, and unlike anything that I had ever seen before," Nicholson said.

What the researchers were seeing was a roughly circular or elliptical hole around 5.3 miles (8.5 km) from rim to rim and up to 131 feet (40 m) from floor to rim. The crater's edge revealed signs of faulting and rock deformation, and perhaps even material thrown out of the main crater that landed around it after the impact. One of the telltale features was a structure under the crater floor where the rock layers were raised above their surroundings. This "central uplift" happens after impacts where the shock pressure is high enough to force the grains in the rock to act like a fluid, Nicholson said; the rock essentially sloshes apart, splashes back together and is frozen in that configuration ever after. ...

The researchers dubbed the structure the Nadir crater after a nearby seamount and reported their findings today (Aug. 17) in the journal Science Advances (opens in new tab).

The crater would have been caused by an asteroid that was 1,213 feet (400 m) wide — roughly the height of the Empire State Building. It would have been a bad day to be a fish. The asteroid hit the ocean bed with the power of 5,000 megatons of TNT, the researchers calculated, and it would have produced a fireball 6.2 miles (10 km) wide. This would have instantly vaporized massive amounts of water and rock. The impact would have created a magnitude-7 earthquake that could have kicked off a series of submarine landslides, all of which would have created some serious waves. The splash at the impact site would have towered at least 1.2 miles (2 km), Nicholson said, and the waves that reached the West African coastline may have been 62 miles (100 km) high. The South American coast, 621 miles (1,000 km) away at the time, would have seen 16-foot-high (5 m) tsunamis. ...
FULL STORY: https://www.livescience.com/end-cretaceous-asteroid-crater-africa
 

EnolaGaia

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Here are the bibliographic details and abstract from the published research report.


The Nadir Crater offshore West Africa: A candidate Cretaceous-Paleogene impact structure
Uisdean Nicholson, Veronica J. Bray , Sean P. S. Gulick And Benedict Aduomahor
Science Advances
17 Aug 2022 Vol 8, Issue 33
DOI: 10.1126/sciadv.abn3096

Abstract
Evidence of marine target impacts, binary impact craters, or impact clusters are rare on Earth. Seismic reflection data from the Guinea Plateau, West Africa, reveal a ≥8.5-km-wide structure buried below ~300 to 400 m of Paleogene sediment with characteristics consistent with a complex impact crater. These include an elevated rim above a terraced crater floor, a pronounced central uplift, and extensive subsurface deformation. Numerical simulations of crater formation indicate a marine target (~800-m water depth) impact of a ≥400-m asteroid, resulting in a train of large tsunami waves and the potential release of substantial quantities of greenhouse gases from shallow buried black shale deposits. Our stratigraphic framework suggests that the crater formed at or near the Cretaceous-Paleogene boundary (~66 million years ago), approximately the same age as the Chicxulub impact crater. We hypothesize that this formed as part of a closely timed impact cluster or by breakup of a common parent asteroid.

SOURCE / FULL REPORT: https://www.science.org/doi/10.1126/sciadv.abn3096
 

EnolaGaia

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Analysis of fossil eggs in China indicates dinosaur diversity had already diminished by the time of the asteroid strike, making the dinosaurs all the more vulnerable to final worldwide extinction.
Dinosaurs Were Already on Their Way Out Before Asteroid Hit, Another Study Finds

The demise of the dinosaurs has long captivated paleontologists. Their mass extinction after a fiery meteorite pummeled Earth some 66 million years ago, as volcanoes erupted and global temperatures rose and fell, was a tumultuous end to the reign of these once-dominant beasts.

But now another study suggests dinosaurs were already on their way out millions of years before the fated meteorite hit, according to an analysis of over 1,000 fossilized eggshells unearthed in central China.

"Dinosaurs went extinct gradually over millions of years, instead of coming to an abrupt end from sudden disasters," study author Qiang Wang of the Chinese Academy of Sciences told the South China Morning Post.

Expect those conclusions to be tested, though. The study weighs into a long and see-sawing debate amongst paleontologists about whether non-avian dinosaurs met an abrupt end or if they were already teetering on the edge of extinction before a 10-kilometer-wide asteroid sealed their fate.

The new research, from a team of geologists and paleontologists working in China, suggests dinosaur biodiversity was fading at least two million years before dinosaurs went extinct, at the end of the Cretaceous, leaving birds as their only living descendants. ...

Its conclusions are based on a collection of egg fossils, including several complete and incomplete dinosaur eggs, preserved in 150-meter-thick layers of rock that were deposited between 68.2 and 66.4 million years ago, right before the curtain came down on the dinosaurs. ...
FULL STORY: https://www.sciencealert.com/dinosa...y-out-before-asteroid-hit-another-study-finds
 

Junopsis

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Surely if birds are decended from raptor type dinosaurs, they never went completely extinct and as previously mentioned, other creatures such as crocodiles and sharks decended from prehistoric versions, along with insects such as dragonflys, so how did these survive where others didnt, i was always under the impression that the nuclear winter type result of asteriod crater debris and /or volcanoes, caused the larger herbivourous sauropods died off due to loss of food followed by the carnivours that preyed on them, or that could be a mandela effect lol
Smaller predators (that is, croc/gator-size, modern shark-size) have more options when food declines. Smaller creatures in general would have done better than those large animals, and so that's how prehistoric lizards, bugs, mammals, birdosaurs, etc. also made it.
 
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