It's not every day a Tyrannosaurus rex is delivered to your front door. But for the University of Washington's Burke Museum in Seattle, Thursday last week was a very special day. They are now the proud custodians of a recently unearthed T. rex skull.

The new dinosaur joins a very exclusive club. T. rex was originally discovered over 100 years ago, and while many scattered teeth and bones have been found since then, only about 15 relatively complete skulls of this dinosaur are known.

It all started just like so many other great fossil finds: with a few bones sticking out of the ground. During a fossil-hunting expedition in Montana last year, two Burke Museum volunteers, Luke Tufts and Jason Love, noticed pieces of fossilised bone protruding from a rocky hillside. "It just looked how we'd been told that bones from a big predatory dinosaur like a T. rex [look]," Love tells The Seattle Times.

When a team of Burke palaeontologists and volunteers began the massive task of digging out the find, they came across ribs and some other bones first, before the rock finally revealed a glimpse of the skull. And what an amazing skull it is: four feet (1.2 metres) long, with a mouth full of enormous teeth.

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Palaeontologists prepare to remove the skull from a fossil dig site in northern Montana. Image: Dave DeMar/Burke Museum.

"Once the skull was almost entirely removed from the hillside, the team began the process of creating its plaster "field jacket" – similar to a cast used to cover a broken bone – to protect it during transportation," explains the museum. 

Moving a plaster-encased T. rex skull is no easy feat. When a hay baler failed to do the trick, a heavy-duty tractor was finally brought in to lift the 2,500-pound payload onto a flatbed truck. From there, the fossil began its long road trip to Seattle.

Based on the size of the animal's head, museum experts estimate it would have been forty feet (12 metres) long from snout to tail, and about 15 years old, when it died. "[This] is going to be an iconic specimen for the Burke Museum and the state of Washington, and will be a must-see for dinosaur researchers as well," says Dr Greg Wilson, Adjunct Curator of Vertebrate Palaeontology at the museum.

The rocks that produced this ancient tyrant are 66.3 million years old, belonging to a geologic layer called the Hell Creek Formation. The area is famous for its Tyrannosaurus fossils, with more found here than anywhere else in the world. These dinosaurs lived right at the very end of the Cretaceous period, less than a million years before the calamitous extinction event that brought the Age of Dinosaurs to a close. 

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The skull gets hoisted up for its road trip to the Burke Museum. Image: Dave DeMar/Burke Museum

T. rex is famous for being one of the largest meat-eating animals that ever walked the earth, armed with huge teeth and bone-crushing jaws. But despite its popularity, there's a lot left to be learned. "Having this [specimen] gives us an opportunity to fill in some gaps about how they lived and how they died," says Wilson.

The skull, still hidden beneath its hard plaster wrapping, currently has a home in the museum lobby. In October, it will move to the lab, where fossil preparators will open it up, finish excavation, and clean and repair the bones. This delicate process could take more than a year. 

In the meantime, Wilson and his team are planning ahead. So far, they've found about 20% of the new skeleton, which isn't shabby at all for a big dinosaur find. But the hunt isn't over. "We're going to go back again next year to find the rest," he says. "There's more in the hill."


Top header image: Daniel Arndt, Flickr