Scientists in US' Utah have unearthed a fossil which suggests Tyrannosaurus rex evolved from a dinosaur smaller than a kangaroo. The species, named 'Moros intrepidus' (harbinger of doom), was roughly around 3 metres long, whereas T-rex is estimated to have been roughly 13 metres long. The fossil has helped close a 70-million-year gap in the T-rex fossil record, researchers said.