Scientists said on Monday they had discovered a new species of dinosaur closely related to Tyrannosaurus rex that strode the plain of North America some 80 million years ago.Thanatotheristes degrootorum – Greek for “Reaper of Death” – is thought to be the oldest member of the T-Rex family yet discovered in northern North America, and would have grown to around eight metres (26 feet) in length.“We chose a name that embodies what this tyrannosaur was as the only known large apex predator of its…