Dinosaurs came out of the dark cold to take over the world after mass extinction in the Triassic

Illustration of a feathered dinosaur eating a mammal during a snowy volcanic winter. Painting by Larry Felder.

Paleontologists often talk a lot about how dinosaurs met their tragic end about 65 million years ago when a giant asteroid hit Earth off the coast of Mexico. But while the story of their demise is pretty well put together, the same can’t be said about the dark period in which they began to rise to the top from their very humble beginnings. What we do know is that they took advantage of another, much earlier, mass extinction about 200 million years ago that wiped out most of the reptiles that dominated the land — and a new study that has excavated in the western desert. China suggests dinosaurs were able to survive the volcanic winters of the late Triassic and early Jurassic thanks to the primitive plumage and other adaptations they gained from living in high latitudes.

Not so naked after all

Hollywood movies and even many textbook illustrations depict dinosaurs as naked beasts roaming through warm and lush rainforests. In the Triassic (252-201 million years ago), when they still had a minor role in the food chain, many dinosaurs lived at higher latitudes, some well above the Arctic Circle. According to new research that uncovered fossilized footprints and rock fragments showing telltale signs of ice, some Triassic dinosaurs endured freezing temperatures. They couldn’t do much about it as all the ‘good’ spots were already taken, but this ability to tolerate the cold would come in handy later on.

Admittedly, the world back then didn’t look like it is today. The planet’s landmass was all merged into a supercontinent called Pangea. The concentration of carbon dioxide in the atmosphere hovered around 2,000 parts per million — about five times higher than today’s levels. As such, surface temperatures were much higher than they are now, but life had time to adapt, because unlike the global warming we experience today, this shift of greenhouse gases in the atmosphere didn’t happen overnight. day, on a geologic time scale.

The hotter tropical and subtropical regions of the supercontinent were dominated by mammal-like reptiles and archosaurs (represented today by birds and crocodiles) living in vast coniferous forests – flowering plants and grasses had yet to develop. The understory of these conifers is said to have been occupied by shrubs and woody vines, where all manner of strange animals lingered, such as the long-necked Tanystropheus or chameleon-like drepanosaurs, which had claws at the end of their tails. Not so many dinosaurs, which only appeared about 240 million years ago. The few dinosaurs that existed were as varied in color as modern birds and had as varied behavior, but none were as large as the late Jurassic and Cretaceous giants, such as the iconic T. rex and Titanosaurs.

Before the mass extinction of the late Triassic, dinosaurs were mainly confined to high latitudes. The few dinosaurs that lived close to the tropics tended to be smaller. The red dot in the northernmost part of this map is the Junggar Basin as it used to be in Pangea. Credit: Olsen et al., Science Advances, 2022.

While ecological niches would trade back and forth with occasional bouts of climate change, things were fairly stable. In general, everyone knew their place — that’s until about 200 million years ago, when Earth experienced another mass extinction event.

We don’t know much about what happened, but the consensus among scientists is that Pangea began to fall apart, causing what we now call the Atlantic Ocean† In the process, the tectonic shifts triggered massive volcanic activity that could have lasted for centuries. These eruptions released even more carbon dioxide into the atmosphere, making the oceans more acidic and causing sea levels to rise dramatically. Virtually all ancient reptiles became extinct, except dinosaurs, pterosaurs, and crocodiles. Marine life was almost completely wiped out by the massive acidification of the ocean and the low oxygen conditions.

But while the massive amounts of greenhouse gases would eventually vastly warm the world’s climate, the volcanic activity also released sulfur dioxide and other aerosols that blocked the sun. Before the never-ending scorching heat, there was an equally deadly global winter, and as luck would have it, dinosaurs were better positioned and adapted to withstand the disaster.

Dinosaurs, both living (birds) and extinct, owed their success in large part to their isolation that allowed them to survive many periods of cold and live in persistently cold environments. In particular, all of the major naked land dinosaur competitors died out during the volcanic winters that resulted from the giant eruptions at the end of the Triassic that made dinosaurs globally ecologically dominant,” Paul Olsen, a geologist at Columbia University Observatory’s Lamont-Doherty Earth, and lead author of the new study, said. ZME Science

“We got dinosaurs all wrong. They are and were not inhabitants of just tropical environments. They are fundamentally cold adapted animals, from the very beginning.”

The reptiles are dead. Long live the dinosaurs!

Olsen and colleagues found fine-grained sandstone and siltstone formations at the bottom of an ancient lake in China’s Junggar Basin. Formed about 206 million years ago, these sediments recorded information about ancient environmental conditions during mass extinctions and beyond. During that time, the excavation site was about 71 degrees north latitude, well above the Arctic Circle.

A shale cliff in northwestern China’s Junggar Basin, where scientists found ice-frayed pebbles amid otherwise fine-grained sediments. Credit: Paul Olsen/Lamont-Doherty Earth Observatory.

These sediments revealed dinosaur footprints, showing that they were active in the region and likely did well. But the researchers also found relatively large pebbles mixed with normally fine sediments, pebbles that shouldn’t be there so far from the shoreline. The only viable explanation is that the pebbles were transported by ice, which moved the rocks — known as ice raft debris (IRD) — to the bottom of the lake as it melted, mixing with the fine sediments.

“The sediments are solid rock and difficult to break down to make comparisons to modern environments, a problem compounded by how difficult it is to accurately measure grain size across four orders of magnitude in a single sample. Fortunately, these problems were addressed early. overcome by Clara Chang, a Columbia graduate student and co-author of the paper,” said Olsen. “We suspect that many researchers believe we have not overcome those challenges. But with persistence and by consistently relying on Occam’s razor Often given the more technical term thrift, in our line of reasoning, we believe we have.

“On our very first day in the field in the Junggar Basin, at the very first stop, we saw what we eventually discovered, grains of sand and pebbles in the first piece of rock we looked at. we said, “That is not true” and we stood there arguing for hours about what it meant. In the weeks that followed, we found similar grains of sand and pebbles in many layers of ice on the lake,” Olsen wrote in an email.

This is essentially the first evidence that dinosaurs can withstand freezing temperatures. They did this thanks to the thermal insulation of primitive springs. Furthermore, there is solid evidence that many dinosaurs were warm-blooded like us, unlike the cold-blooded reptiles who depended on the sun to regulate their temperature and metabolism. So when the global cold came, the dinosaurs were ready — and they rushed in to take over once everyone else had perished. At least, that’s what this research suggests. Many will disagree, but we are finally getting closer to understanding how dinosaurs become so wildly successful.

The dinosaurs are dead. Long live the mammals!

This was the beginning of the age of dinosaurs, and they had a pretty good run. That is until, you know, that asteroid happened. But in the wake of another great extinction, came the age of mammals and, eventually, the age of humanity. You’re probably seeing a pattern here: nature is in equilibrium and the ecosystem is dominated by one particular group, until a global disaster occurs and the entire world order goes through an upheaval. The question is who now lurking in the shadows will inherit the Earth after we are all long dead?

“She [dinosaurs] were isolated from the cold by prototyping and could survive the cold of the volcanic winters at the end of the Triassic, 202 million years ago. The same was true for the small dinosaurs (birds) during the winter impact at the famous KT (Cretaceous-Paleogene) boundary 66 million years ago, when all large animals became extinct due to a cut-off from light and extreme cold. Both mass extinctions occurred because of unusual cold events caused by physical phenomena, but the KT also included darkness that hit large animals as it cut off the large amounts of food they needed,” Olsen said.

The findings appeared in the journal scientific progress

#Dinosaurs #dark #cold #world #mass #extinction #Triassic

Leave a Comment

Your email address will not be published.