At any one time, 20,000 Tyrannosaurus rex roamed the Earth, calculation determines
Nature reports: Ever wondered how many Tyrannosaurus rex ever roamed the Earth? The answer is 2.5 billion over the two million or so years for which the species existed, according to a calculation published today in Science1. The figure has allowed researchers to estimate just how exceedingly rare it is for animals to fossilize. Palaeontologists led by Charles Marshall at the University of California, Berkeley, used a method employed by ecologists studying contemporary creatures to estimate the population density of…