Researchers at a top U.S. laboratory announced Tuesday that they have produced the highest resolution scan ever done of the inner workings of a fossilized tyrannosaur skull using neutron beams and high-energy X-rays, resulting in new clues that could help paleontologists piece together the evolutionary puzzle of the monstrous T. rex.

Officials with Los Alamos National Laboratory and the New Mexico Museum of Natural History and Science presented some of their findings after peering deeper in into the skull of a "Bisti Beast," a T. rex relative that lived millions of years ago in what is now northwestern New Mexico.

The images detail the dinosaur's brain and sinus cavity, the pathways of some nerves and blood vessels and teeth that formed but never emerged.

"The CT scans help us figure out how the different species within the T. rex family related to each other and how they evolved," said Thomas Williamson, the museum's curator of paleontology.

T. rex and other tyrannosaurs were huge, dominant predators, but they evolved from much smaller ancestors.

The fossilized remnants of the Bisti Beast, or Bistahieversor sealeyi, were found in 1996 in the Bisti/De-Na-Zin badlands near Farmington, N.M.

The species lived about 10 million years before T. rex, and scientists have said it represents the foundation of the tyrannosaurs with its big-headed, bone-crushing characteristics and small forelimbs.

Williamson said the Bisti Beast was a surviving member of a lineage that retained many primitive features from even farther back than when tyrannosaurs underwent their transition to crushing bones.

Largest object scanned

Officials said the dinosaur's skull is the largest object to date for which full, high-resolution neutron and X-ray CT scans have been done at Los Alamos. The technology is typically used for the lab's work on defence and national security.

The thickness of the skull required stronger X-rays than those typically available to penetrate the fossil, the lab said. That's where the lab's electron and proton accelerators came in.

"It turns out that high-energy neutrons are an interesting and unique way to image something of this size," said Ron Nelson, who works with the lab's physics division. The skull spans 102 centimetres.

The team, which included staff from the University of New Mexico and the University of Edinburgh, is scheduled to present its work at a paleontology conference in Canada next week.