I know that T. rex used to be considered the biggest meat eating theropod dinosaur until the discovery of Giganotosaurus, but Spinosaurus is now considered the biggest theropod of all time. Who first considered Spinosaurus to be larger than T. rex. Is it possible that the emergence of giant carcharodontosaurs and tyrannosaurs in North America and Asia prompted ankylosaurids to develop tail clubs to fend off those predators.