Tyrannosaurus Rex was 40 feet long and weighed in at 6 tons. Scientists have now discovered that these ultimate predators were also much faster than previously believed.
500 pounds in a single bite
Four-foot jaws, raggedly studded with 7-inch teeth that could crush bone and consume 500 pounds in a single bite.
T-Rex was the ultimate predator, the undisputed master of its Cretaceous world. Every living thing must have trembled when this natural born killer was on the prowl. Because apart from being deadly, they were very fast.
Scientists were able to calculate the speed of the beasts from foot prints they left behind 163 million years ago. Their research is reported in the science journal Nature.
A megalosaurus, a huge hunter-killer and relative of T- rex, made its mark in history when it went for a run in what is now Oxfordshire.
When the prints were made, the quarry was in a coastal plain resembling the Florida Everglades, 20 miles from land.
Some freak of time and geology preserved the foot prints. Sediments buried them. Continents shifted. The landscape sank beneath the waves, and then emerged again.
The prints were used to calculate that dinosaurs such as Tyrannosaurus Rex could run at speeds of up to 19 mph.
The size of the footprints, and the distance and the angles between them, were all they had to go on. The length of the foot gave a clue to the creature's height at the hip. When it walked - at an estimated 4.25mph - it had a stride of 2.7 metres. When it accelerated, its stride stretched to 5.6 metres and its speed increased fourfold.
The discovery could reveal more about how Jurassic predators moved and hunted - even provide clues to the behaviour of dinosaurs.
Dr Julia Day, a palaeontologist at the University of Cambridge in England, suspects that the megalosauruses were out hunting. They were following a herd of sauropods, waiting to strike.
"People have speculated that they were pack hunters," said Dr Day. "This could be evidence that the megalosauruses were hunting together."
Their footprints were discovered by quarrymen at Ardley in Oxfordshire millions of years after the event. They scraped away the rock and clay and exposed one of the most extensive dinosaur track ways in the world.