Billions of T. rex lived and died in dino era

摘要

THE reign of the dinosaurs saw a total of 2.5 billion Tyrannosaurus rex roam Earth before extinction. Charles Marshall at the University of California, Berkeley, and his colleagues used body mass and population density to come up with the estimate. Larger animals tend to have a larger individual range, because they need more food to support their body mass than smaller animals. This means body mass is inversely correlated with population density.Previous analysis of T. rex fossils shows the average body mass of an adult was about 5200 kilograms. The team also used climate models and the locations of T. rex remains to estimate that the total geographic range of the species was about 2.3 million square kilometres across North America.Using these figures and data from living species, the team estimated that there was around one T. rex for every 100 square kilometres in North America. "This would mean there was about 20,000 adult T. rex at any given time," says Marshall.