Chuck Bednar for redOrbit.com – @BednarChuck
Wild swings in climate that featured droughts, intense heat, and wildfires were the reasons behind plant-eating dinosaurs’ scarcity around the equator, new research published in the latest Proceedings of the National Academy of Sciences revealed.
Only a handful of carnivorous dinosaurs lived in the tropics–in large part due to the lack of herbivores. Why this was, though, is a question that’s plagued paleontologists for decades–until recently, after an international team of scientists created a model of the climate and ecology from more than 200 million years ago.
“Our data suggest it was not a fun place,” co-author Randall Irmis, the paleontology curator at the Natural History Museum of Utah and an assistant professor at the University of Utah, said in a statement. “It was a time of climate extremes that went back and forth unpredictably and large, warm-blooded dinosaurian herbivores weren’t able to exist nearer to the equator.”
The study, which the researchers claim is the first to examine a detailed analysis of the climate and ecology during the emergence of the dinosaurs, determined that there was not enough plant life in the tropics to serve as food for the hungry herbivores.
Conditions were similar to the western US today
As part of their research, Irmis, lead investigator Jessica Whiteside from the UK’s University of Southampton and their fellow researchers studied Chinle Formation rocks, which were deposited by streams and rivers between 205 and 215 million years ago, at Ghost Ranch in New Mexico.
The Ghost Ranch site is home to many fossils from the Late Triassic Period, and at that time, the area would have been part of the Pangea and located close to the equator at latitudes close to that of current-day southern India. They analyzed fossils, charcoal remnants from ancient wildfires, and stable isotopes from organic matter and carbonate nodules that formed in ancient soil.
Based on the fossil evidence, the authors found that dinosaurs accounted for less than 15 percent of vertebrate animal remains, and were outnumbered by the predecessors of modern crocodiles and alligators. The dinosaurs that they did find were primarily small, carnivorous theropods, and the fossil record shows no evidence of sauropodomorphs, the dominant plant-eaters of the era, at the study site or elsewhere in low-latitude Triassic Pangaea, they explained.
Based on their research, they were able to discern that the climate shifts that affected the region included periods of extended drought that hampered plant productivity, a drastic variation in the burn temperatures of wildfires, and drastic changes in precipitation levels that would have caused plants to die off, thus fuelling hotter fires and further damaging the ecosystem.
“The conditions would have been something similar to the arid western United States today, although there would have been trees and smaller plants near streams and rivers and forests during humid times,” Whiteside explained. “The fluctuating and harsh climate with widespread wild fires meant that only small two-legged carnivorous dinosaurs… could survive.”
—–
Follow redOrbit on Twitter, Facebook, Google+, Instagram and Pinterest.
Comments