EVEN the weakest parts of Tyrannosaurus rex's skull were built to crush bones and rip flesh.

Many joints in the fearsome creature's skull were held in place loosely by ligaments, which studies of other animals have shown to be weaker than fused joints. But when Emily Rayfield of the University of Cambridge created a computer model of the internal forces set up by biting and ripping, she found that the results were neatly mirrored by the structure of the T. rex skull.

The strongest compression and shearing forces produced by biting and ripping came at the mid-point of the skull, where T. rex had massive nasal bones that fused at an early age. Tensional forces that tended to pull the skull bones apart arose in other areas, where the joints between bones remained mobile. The flexing of the mobile joints kept the bones from breaking, Rayfield says (Proceedings of the Royal Society B, DOI: 10.1098/rspb.2004.2755).

The analysis ties in with the "bite-and-tear" feeding strategy suggested by puncture and scratch marks on the bones of T. rex's presumed prey, says tyrannosaur expert Tom Holtz of the University of Maryland at College Park.