Researchers have demonstrated that the extinction of dinosaurs 65 million years ago paved the way for mammals to get bigger about a thousand times bigger than they had been.
The study, released today in the prestigious journal Science, is the first to quantitatively explore the patterns of body size of mammals after the demise of the dinosaurs.
The research, funded by a National Science Foundation Research Coordination Network grant, was led by scientists at the University of New Mexico and brought together an international team of palaeontologists, evolutionary biologists, and macroecologists from universities around the world.
To document what happened to mammals after the extinction of dinosaurs, researchers collected data on the maximum size for major groups of land mammals on each continent, including Perissodactyla, odd-toed ungulates such as horses and rhinos; Proboscidea, which includes elephants, mammoth and mastodon Xenarthra; the anteaters, tree sloths, and armadillos; as well as a number of other extinct groups. The researchers spent three years compiling the large database.
Dr Alistair Evans, a co-author on the paper and an Australian Research Fellow at Monash University, said the database is unique.
"The database allows us for the first time to compare maximum size of mammals on different continents since the extinction of the dinosaurs."
The goal of the research was to revisit key questions about size, specifically in mammals.
"Size affects everything about an animal, from feeding and reproduction to extinction. We really wanted to know how big the many different groups of mammals evolved to be, and how quickly they got there - we were looking for the biggest of the big," said Dr Evans.
Researchers found that mammals grew from a size of about ten kilograms when they were sharing the Earth with dinosaurs to a maximum of 17 tonnes afterwards. Moreover, the pattern
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