A CO2 dip may have helped dinosaurs walk from South America to Greenland

A new paper updates estimates of when raspberry dinosaurs should cross North America on a trip north to reach Greenland, revealing the wonder of a potentially interesting climate. help them along the way.

The study, published today in Proceedings of the National Academy of Sciences, written by Dennis Kent, an adjunct research scientist at the Lamont-Doherty World Observatory at Columbia University, and Lars Clemmensen from the University of Copenhagen.

Previous estimates suggest that sauropodomorphs – a group of long-legged herbivorous dinosaurs that eventually introduced Brontosaurus and Brachiosaurus – reached Greenland sometime between 225 and 205 million years ago. But by carefully matching ancient magnetic patterns in rock layers at fossil sites across South America, Arizona, New Jersey, Europe and Greenland, the new study offers a more accurate estimate: it appears that sauropodomorphs appeared in the area now known about 214 million years ago. At the time, all the continents were connected together, making up the supercontinent Pangea.

With this new and more accurate estimate, the authors had another question. Fossil records show that sauropodomorph dinosaurs first appeared in Argentina and Brazil around 230 million years ago. So why did it take them so long to expand into the Northern Hemisphere?

“In principle, the dinosaurs could have walked from almost one pole to another,” Kent explained. “There was no ocean between them. There were no big mountains. But nonetheless it took 15 million years. It’s like snails made faster.” He pretends to walk a dinosaur herdsman just one mile a day, it would take less than 20 years to make the journey from South America to Greenland.

Interestingly, the Earth was in the midst of a dramatic drop in atmospheric CO2 around the time the sauropodomorphs would have been migrating 214 million years ago. Until about 215 million years ago, CO2 levels were very high in the Triassic period, at around 4,000 parts per million – about 10 times higher than today. But between 215 and 212 million years ago, the CO2 density dropped by half, falling to around 2,000ppm.

While the timing of these two events – the CO2 plummeting and the sauropodomorph migration – may be a true coincidence, Kent and Clemmensen believe they are related. In the paper, they suggest that the calmer levels of CO2 may have helped remove potential climate barriers for the sauropodomorphs in America. Nice to take.

On Earth, areas around the equator are hot and humid, but nearby areas in low latitudes tend to be very dry. Kent and Clemmensen say that, on a planet full of CO2, the differences between these climate zones may have been true – perhaps too difficult for the sauropodomorph dinosaurs to cross.

“We know with higher CO2, the drier and the wetter the wetter,” Kent said. 230 million years ago, the high CO2 conditions may have made the arid belts too dry to support large raspberry shoots that need to eat a lot of vegetation to survive. The tropics may have been locked in wet conditions, like a monsoon that may not have been particularly suitable for sauropodomorphs. There is little evidence that they emerged from the central, mid-latitude habitats in which they were modified in Argentina and Brazil.

But when CO2 levels decreased 215-212 million years ago, the tropical regions may have become milder, and the deciduous regions less dry. There may have been some passages, such as rivers and streams of lakes, that would have helped sustain the raspberries on the 6,500-mile journey to Greenland, where their fossils are now abundant. Back then, Greenland would have a temperate climate similar to the state of New York state today, but with much milder winters, with no polar ice sheets at the time.

“When they got to Greenland, they looked like they had settled in,” said Kent. “They were hanging around like a fossil record long after that.”

The idea that a reduction in CO2 may have helped these dinosaurs overcome an unpredictable but plausible climate barrier is likely to be supported by the fossil record, Kent said. . Sauropodomorph body fossils have not been found in the tropical and arid regions of this period – although their finds turn up from time to time – suggesting that they did not inhabit these areas.

Next, Kent hopes to continue working to better understand the massive CO2 depletion, including what caused it and how quickly CO2 levels fell.

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The Lamont-Doherty Earth Observatory is the home of Columbia University for the study of earth science. His scientists develop a basic knowledge of the origin, evolution and future of the natural world, from the deepest interior of the planet to the outer regions of the atmosphere, on all continents. land and in all oceans, providing a reasonable basis for the difficult choices facing humanity. http: // www.ldeo.Colombia.edu | @LamontEarth

The Earth Institute, Columbia University mobilizes the sciences, education and public policy to achieve sustainable ground. http: // www.land.Colombia.edu.