JOIN USIn a major finding, scientists have discovered a Tyrannosaurus rex fossil, including a very complete skull, vertebrae, ribs, hips and jaw bones, which they estimate to be about 20 per cent of the dinosaur.
Researchers led by Gregory P Wilson from University of Washington (UW) in the US discovered the T rex during an expedition to the Hell Creek Formation in northern Montana - an area that is world-famous for its fossil dinosaur sites.
Two volunteers from UW's Burke Museum initially discovered pieces of fossilised bone protruding from a rocky hillside. The bones' large size and honeycomb-like structure indicated they belonged to a carnivorous dinosaur.
Upon further excavation, researchers discovered the T rex skull along with ribs, vertebrae, and parts of the jaw and pelvis.
T rex was one of the largest meat-eating dinosaurs to ever roam the Earth. Measuring an average of 12-metres long and four to six-metres tall, T rex was a fierce predator with serrated teeth and large jaws.
Fossil evidence shows it ate other dinosaurs like Edmontosaurus and Triceratops, with crushed bones from the animals even showing up in its fossilised poop.
T rex lived about 66-68 million years ago in forested river valleys in western North America during the late Cretaceous Period, researchers said.
The T rex is nicknamed the "Tufts-Love Rex" in honour of the two volunteers who discovered it, Jason Love and Luke Tufts.
The skull is about one metre long and weighs about 1,133 kilogrammes in its protective plaster jacket. Excavation in the field showed the right side of the skull from base to snout, including teeth.
Researchers believe it is very probable the other side of the skull is present, but will need to carefully remove the rock surrounding the fossil before they can determine its completeness.
Based on the size of its skull, researchers estimate this dinosaur is about 85 per cent the size of the largest T rex found to date.
The Tufts-Love Rex is 66.3 million years old. T rex lived at the end of the Cretaceous Period, and became extinct during the Cretaceous-Paleogene mass extinction 66 million years ago.
Researchers could determine that the Tufts-Love Rex lived at the very end of the Cretaceous because it was found at the bottom of a hill; a rock layer at the top of that hill marks the Cretaceous-Paleogene mass extinction.
Based on the size of the skull - a good indicator of T rex age - researchers estimate the dinosaur was about 15 years old when it died. Adult T rex lived up to 25-30 years.