Dinosaurs took over amid ice, not warmth, says a new study of ancient mass extinction (2022)

Dinosaurs took over amid ice, not warmth, says a new study of ancient mass extinction (1)

Many of us know the conventional theory of how the dinosaurs died 66 million years ago: in Earth's fiery collision with a meteorite, and a following global winter as dust and debris choked the atmosphere. But there was a previous extinction, far more mysterious and less discussed: the one 202 million years ago, which killed off the big reptiles who up until then ruled the planet, and apparently cleared the way for dinosaurs to take over. What caused the so-called Triassic-Jurassic Extinction, and why did dinosaurs thrive when other creatures died?

We know that the world was generally hot and steamy during the Triassic Period, which preceded the extinction, and during the following Jurassic, which kicked off the age of dinosaurs. However, a new study turns the idea of heat-loving dinosaurs on its head: It presents the first physical evidence that Triassic dinosaur species—then a minor group largely relegated to the polar regions—regularly endured freezing conditions there. The telltale indicators: dinosaur footprints along with odd rock fragments that only could have been deposited by ice. The study's authors say that during the extinction, cold snaps already happening at the poles spread to lower latitudes, killing off the coldblooded reptiles. Dinosaurs, already adapted, survived the evolutionary bottleneck and spread out. The rest is ancient history.

"Dinosaurs were there during the Triassic under the radar all the time," said Paul Olsen, a geologist at Columbia University's Lamont-Doherty Earth Observatory, and lead author of the study. "The key to their eventual dominance was very simple. They were fundamentally cold-adapted animals. When it got cold everywhere, they were ready, and other animals weren't."

The study, based on recent excavations in the remote desert of northwest China's Junggar Basin, was just published in the journal Science Advances.

Dinosaurs are thought to have first appeared during the Triassic Period in temperate southerly latitudes about 231 million years ago, when most of the planet's land was joined together in one giant continent geologists call Pangaea. They made it to the far north by about 214 million years ago. Until the mass extinction at 202 million years, the more expansive tropical and subtropical regions in between were dominated by reptiles including relatives of crocodiles and other fearsome creatures.

(Video) Dinosaurs took over amid ice, not warmth, says a new study of ancient mass extinction

During the Triassic, and for most of the Jurassic, atmospheric concentrations of carbon dioxide ranged at or above 2000 parts per million—five times today's levels—so temperatures must have been intense. There is no evidence of polar ice caps then, and excavations have shown that deciduous forests grew in polar regions. However, some climate models suggest that the high latitudes were chilly some of the time; even with all that CO2, they would have received little sunlight much of the year, and temperatures would decline at least seasonally. But until now, no one has produced any physical evidence that they froze.

At the end of the Triassic, a geologically brief period of perhaps a million years saw the extinction of more than three quarters of all terrestrial and marine species on the planet, including shelled creatures, corals and all sizable reptiles. Some animals living in burrows, such as turtles, made it through, as did a few early mammals. It is unclear exactly what happened, but many scientists connect it to a series of massive volcanic eruptions that could have lasted hundreds of years at a stretch. At this time, Pangaea started to split apart, opening what is now the Atlantic Ocean, and separating what are now the Americas from Europe, Africa and Asia. Among other things, the eruptions would have caused atmospheric carbon dioxide to skyrocket beyond its already high levels, causing deadly temperatures spikes on land, and turning ocean waters too acid for many creatures to survive.

The authors of the new study cite a third factor: During the eruptions' fiercest phases, they would have belched sulfur aerosols that deflected so much sunlight, they caused repeated global volcanic winters that overpowered high greenhouse-gas levels. These winters might have lasted a decade or more; even the tropics may have seen sustained freezing conditions. This killed uninsulated reptiles, but cold-adapted, insulated dinosaurs were able to hang on, say the scientists.

The researchers' evidence: fine-grained sandstone and siltstone formations left by sediments in shallow ancient lake bottoms in the Junggar Basin. The sediments formed 206 million years ago during the late Triassic, through the mass extinction and beyond. At that time, before landmasses rearranged themselves, the basin lay at about 71 degrees north, well above the Arctic Circle. Footprints found by the authors and others show that dinosaurs were present along shorelines. Meanwhile, in the lakes themselves, the researchers found abundant pebbles up to about 1.5 centimeters across within the normally fine sediments. Far from any apparent shoreline, the pebbles had no business being there. The only plausible explanation for their presence: they were ice-rafted debris (IRD).

(Video) Study of Ancient Mass Extinction Reveals Dinosaurs Took Over Earth Amid Ice, Not Warmth...

Briefly, IRD is created when ice forms against a coastal landmass and incorporates bits of underlying rock. At some point the ice becomes unmoored and drifts away into the adjoining water body. When it melts, the rocks drop to the bottom, mixing with normal fine sediments. Geologists have extensively studied ancient IRD in the oceans, where it is delivered by glacial icebergs, but rarely in lake beds; the Junggar Basin discovery adds to the scant record. The authors say the pebbles were likely picked up during winter, when lake waters froze along pebbly shorelines. When warm weather returned, chunks of that ice floated off with samples of the pebbles in tow, and later dropped them.

"This shows that these areas froze regularly, and the dinosaurs did just fine," said study co-author Dennis Kent, a geologist at Lamont-Doherty.

Dinosaurs took over amid ice, not warmth, says a new study of ancient mass extinction (3)

How did they do it? Evidence has been building since the 1990s that many if not all non-avian dinosaurs including tyrannosaurs had primitive feathers. If not for flight, some coverings could have used for mating display purposes, but the researchers say their main purpose was insulation. There is also good evidence that, unlike the cold-blooded reptiles, many dinosaurs possessed warm-blooded, high-metabolism systems. Both qualities would have helped dinosaurs in chilly conditions.

"Severe wintery episodes during volcanic eruptions may have brought freezing temperatures to the tropics, which is where many of the extinctions of big, naked, unfeathered vertebrates seem to have occurred," said Kent. "Whereas our fine feathered friends acclimated to colder temperatures in higher latitudes did OK."

The findings defy the conventional imagery of dinosaurs, but some prominent specialists say they are convinced. "There is a stereotype that dinosaurs always lived in lush tropical jungles, but this new research shows that the higher latitudes would have been freezing and even covered in ice during parts of the year," said Stephen Brusatte, a professor of paleontology and evolution at the University of Edinburgh. "Dinosaurs living at high latitudes just so happened to already have winter coats [while] many of their Triassic competitors died out."

(Video) The dinosaurs took over in the middle of the ice, not heat, says a new study of ancient mass extinct

Randall Irmis, curator of paleontology at the Natural History Museum of Utah, and specialist in early dinosaurs, agrees. "This is the first detailed evidence from the high paleolatitudes, the first evidence for the last 10 million years of the Triassic Period, and the first evidence of truly icy conditions," he said. "People are used to thinking of this as being a time when the entire globe was hot and humid, but that just wasn't the case."

Olsen says the next step to better understand this period is for more researchers to look for fossils in former polar areas like the Junggar Basin. "The fossil record is very bad, and no one is prospecting," he said. "These rocks are gray and black, and it is much harder to prospect [for fossils] in these strata. Most paleontologists are attracted to the late Jurassic, where it's known there are many big skeletons to be had. The paleo-Arctic is basically ignored."

The study was co-authored Jingeng Sha and Yanan Fang of Nanjing Institute of Geology and Paleontology; Clara Chang and Sean Kinney of Lamont-Doherty Earth Observatory; Jessica Whiteside of the University of Southampton; Hans-Dieter Sues of the Smithsonian Institution; Morgan Schaller of Rensselaer Polytechnic Institute; and Vivi Vajda of the Swedish Museum of Natural History.

Explore further

Low volcanic temperature ushered in global cooling and the thriving of dinosaurs

(Video) How A Mass Extinction Helped the Dinosaurs

More information:Paul Olsen et al, Arctic ice and the ecological rise of the dinosaurs, Science Advances (2022). DOI: 10.1126/sciadv.abo6342. www.science.org/doi/10.1126/sciadv.abo6342

Journal information:Science Advances

Provided byColumbia University

Citation: Dinosaurs took over amid ice, not warmth, says a new study of ancient mass extinction (2022, July 1) retrieved 30 July 2022 from https://phys.org/news/2022-07-dinosaurs-ice-warmth-ancient-mass.html

This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.

(Video) What is only dinosaur lineage to survive the mass extinction event? #shorts #dinosaur #dinosaurs

FAQs

Dinosaurs took over amid ice, not warmth, says a new study of ancient mass extinction? ›

The study's authors say that during the extinction, cold snaps already happening at the poles spread to lower latitudes, killing off the coldblooded reptiles. Dinosaurs, already adapted, survived the evolutionary bottleneck and spread out. The rest is ancient history.

Did dinosaurs experience ice ages? ›

This theory has been largely discarded for one simple reason: scientists have not found any evidence of an ice age occurring during the life of the dinosaurs.

How Did climate change lead to the extinction of dinosaurs? ›

Gradual Change

Perhaps the warm, wet climate gradually changed to a drier, cooler one. In many areas, the fossil record shows tropical vegetation was replaced by woodland plants. Once again, it is possible that the dinosaurs were not adapted to the new environment and therefore became extinct.

Why were dinosaurs not able survive the Ice Age? ›

Lower temperatures caused ice to form over the North and South poles and the oceans to become colder. Because the dinosaurs were cold-blooded–meaning they obtained body heat from the sun and the air–they would not have been able to survive in significantly colder climates.

What caused the mass extinction at the end of the Jurassic period? ›

Some have hypothesized that an impact from an asteroid or comet may have caused the Triassic–Jurassic extinction, similar to the extraterrestrial object which was the main factor in the Cretaceous–Paleogene extinction about 66 million years ago, as evidenced by the Chicxulub crater in Mexico.

What killed the ice age? ›

Scientists have found evidence in sediment cores to support a controversial theory that an asteroid or a comet slammed into Earth and helped lead to this extinction of ice age animals and cooling of the globe. It's called the Younger Dryas Impact Hypothesis and was first suggested in 2007.

What ended the ice age? ›

New University of Melbourne research has revealed that ice ages over the last million years ended when the tilt angle of the Earth's axis was approaching higher values.

How long would an impact winter last? ›

The impact winter did not last long, however. Over a few months or possibly a few decades, the dust and soot fell out of the atmosphere and rained down onto the land and oceans, allowing sunlight to warm the planet once again.

Is the extinction of dinosaurs a theory? ›

Harvard Researchers Propose New Theory Harvard researchers say a comet from deep space — not an asteroid from the belt past Mars — was responsible for the mass extinction.

How warm was the Earth during the dinosaurs? ›

The Cretaceous period is an archetypal example of a greenhouse climate. Atmospheric pCO2 levels reached as high as about 2,000 ppmv, average temperatures were roughly 5°C–10°C higher than today, and sea levels were 50–100 meters higher [O'Brien et al., 2017; Tierney et al., 2020].

Did anything survive the ice age? ›

Almost all hominins disappeared during the Ice Age. Only a single species survived. But H. sapiens had appeared many millennia prior to the Ice Age, approximately 200,000 years before, in the continent of Africa.

Will there be another ice age? ›

There have been five big ice ages in Earth's 4.5-billion-year lifespan and scientists say we're due for another one. The next ice age may not occur for another 100,000 years.

Did any animals survive the ice age? ›

As the climate became warmer after the last ice age, the woolly rhinoceros, woolly mammoth and wild horse went extinct, but the reindeer, bison and musk ox survived. Reindeer managed to find safe habitat in high arctic regions where today they have few predators or competitors for limited resources.

Are we in a mass extinction event? ›

The planet has experienced five previous mass extinction events, the last one occurring 65.5 million years ago which wiped out the dinosaurs from existence. Experts now believe we're in the midst of a sixth mass extinction.

How mankind is driving the next mass extinction? ›

The study states that this mass extinction differs from previous ones because it is entirely driven by human activity through changes in land use, climate, pollution, hunting, fishing and poaching. The effects of the loss of these large predators can be seen in the oceans and on land.

What are the big 5 mass extinctions? ›

Top Five Extinctions
  • Ordovician-silurian Extinction: 440 million years ago.
  • Devonian Extinction: 365 million years ago.
  • Permian-triassic Extinction: 250 million years ago.
  • Triassic-jurassic Extinction: 210 million years ago.
  • Cretaceous-tertiary Extinction: 65 Million Years Ago.

What was alive during the ice age? ›

During the cold glacial times, icons like the woolly mammoth, steppe bison and scimitar cat roamed the treeless plains alongside caribou, muskox and grizzly bears. In still older times, where temperatures were similar to today, giant beavers, mastodons and camels browsed the interglacial forests.

What was the biggest animal during the ice age? ›

Lions roamed the land

Although the bears in ice age North America were the biggest and most powerful carnivores, they had some stiff competition. Twenty thousand years ago, lions roamed the entire planet.

Did the ice age cause extinction? ›

The Great Ice Age that occurred during the Pleistocene era (which began about 2 million years ago and ended 10,000 years ago) also caused the extinction of many plants and animal species. This period is of particular interest because it coincides with the evolution of the human species.

Did humans survive the last ice age? ›

Humans were (and still are) definitely alive during the Ice Age. Scientists and anthropologists have found evidence of human remains existing nearly 12,000 years ago. The current interglacial period began around 10,000 years ago. Before then, most humans lived in the Southern Hemisphere.

What will cause the next ice age? ›

When plate-tectonic movement causes continents to be arranged such that warm water flow from the equator to the poles is blocked or reduced, ice sheets may arise and set another ice age in motion.

How long will it be until the next ice age? ›

The next ice age almost certainly will reach its peak in about 80,000 years, but debate persists about how soon it will begin, with the latest theory being that the human influence on the atmosphere may substantially delay the transition. This is no mere intellectual exercise.

How long was the ice age after the dinosaurs? ›

The glacial periods lasted longer than the interglacial periods. The last glacial period began about 100,000 years ago and lasted until 25,000 years ago. Today we are in a warm interglacial period.

How many ice ages have there been since the dinosaurs? ›

At least five major ice ages have occurred throughout Earth's history: the earliest was over 2 billion years ago, and the most recent one began approximately 3 million years ago and continues today (yes, we live in an ice age!). Currently, we are in a warm interglacial that began about 11,000 years ago.

Was there an ice age in the Mesozoic Era? ›

There were no actual ice ages during Mesozoic. A team of researchers from the U.S. Brown University has produced a climate description of Pangaea in the Triassic period using samples taken from the seabed of lakes from Nova Scotia to Georgia.

Did humans live during the ice age? ›

Wait, there were humans during the ice age?!

Yes, people just like us lived through the ice age. Since our species, Homo sapiens, emerged about 300,000 years ago in Africa, we have spread around the world. During the ice age, some populations remained in Africa and did not experience the full effects of the cold.

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