This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Keeping to warm climates throughout their 250-million-year history may have helped crocodiles and their relatives survive the asteroid that killed the dinosaurs, finds a new study led by UCL (University College London) researchers. The study, published in Science Advances, looked at more than 7,000 fossils and records of over 400 species both living and extinct, comparing these with computer reconstructions of Earth's climate and geography over 245 million years.
The team found that, rather than adapting to new climates, crocodiles and their relatives followed warm climates wherever they moved, in hot periods spreading as far as Antarctica, in colder ones retreating to the tropics. The researchers also simulated how the climate might have changed following the asteroid impact 66 million years ago and concluded that, in all but the most extreme scenarios, warm regions near the equator and in the subtropics stayed suitable for crocodile relatives. Earlier modeling by members of the same team showed that suitable climates for nonavian dinosaurs (i.e., the ones that went extinct) shrank far more drastically.
Alfio Alessandro Chiarenza, based at UCL Earth Sciences, said, "The asteroid did not make the whole planet equally hostile to every group. "Crocodiles' long-standing preference for warm environments may have placed survivors exactly where suitable climates held up best, like around the equator. These refuges could have sheltered populations that later recovered and radiated out." The crocodile lineage, known to scientists as pseudosuchians, appeared at a similar time as the dinosaurs and has since survived two of Earth's five mass extinctions.
Although crocodiles and their relatives appear very similar to each other today, the ancestors of this group were much more diverse, including heavily armored plant eaters, land-dwelling predators and giants weighing more than a ton. Well-known pseudosuchians include the giant predator Sarcosuchus, the "super croc" that grew up to 12 meters (39 feet) long, and Postosuchus, which hunted solely on land and could move on two legs as well as on all fours. Chiarenza said, "Crocodiles are often called living fossils, but their ancestors and relatives changed enormously throughout their history, ranging from giants the size of a bus that could have devoured a T. rex, to small, cute animals with the face of a pug.
"Our study shows that, despite all this diversity, what stayed surprisingly consistent was their relationship with climate." For their study, the research team inferred the temperature and rainfall preferences of 400 species, using fossil records, evolutionary trees and detailed mapping of where crocodile species live today. They then mapped these species' suitable habitats over time, using reconstructions of Earth's climate and geography. They found that crocodile relatives largely tracked warm climates around the globe.
During the hothouse of the early Eocene, about 50 million years ago, when global temperatures were about 10°C higher than today and polar regions were ice-free, they lived at high latitudes in North America, Europe and Antarctica. When the planet cooled in the millions of years that followed, their range shrank back toward the tropics. Discover the latest in science, tech, and space with over 100,000 subscribers who rely on Phys.org for daily insights. d research that matter—daily or weekly.
Extract — continue reading at the source.
