Tiny T.rex ancestor throws light on predator evolution

As every school child knows, Tyrannosaurus rex was an enormous and ferocious apex predator. Right now, however, at least among paelaeontologists, it is a tiny little relative of the big beast that is attracting all the attention.
In stark contrast to T.rex, most tyrannosauroid dinos were small animals – subordinate hunters that enjoyed survival, if not exactly dominion, for 100 million years.