T. rex skull mechanics explained in new paper

[bh480@scn.org]

From: Ben Creisler bh480@usc.edu
In case this paper has not been mentioned yet, there is a 
new paper about T. rex posted for the  online version of  
Proceedings: Biological Sciences ISSN: 0962-8452 (Paper) 
1471-2954 (Online) 
http://www.journals.royalsoc.ac.uk/

Cranial mechanics and feeding in Tyrannosaurus rex
Emily J. Rayfield A1 
Abstract: 
It has been suggested that the large theropod dinosaur 
Tyrannosaurus rex was capable of producing extremely 
powerful bite forces and resisting multi-directional 
loading generated during feeding. Contrary to this 
suggestion is the observation that the cranium is composed 
of often loosely articulated facial bones, although these 
bones may have performed a shock-absorption role. The 
structural analysis technique finite element analysis 
(FEA) is employed here to investigate the functional 
morphology and cranial mechanics of the T. rex skull. In 
particular, I test whether the skull is optimized for the 
resistance of large bi-directional feeding loads, whether 
mobile joints are adapted for the localized resistance of 
feeding-induced stress and strain, and whether mobile 
joints act to weaken or strengthen the skull overall. The 
results demonstrate that the cranium is equally adapted to 
resist biting or tearing forces and therefore 
the 'puncture-pull' feeding hypothesis is well supported. 
Finite-element-generated stress-strain patterns are 
consistent with T. rex cranial morphology: the maxilla-
jugal suture provides a tensile shock-absorbing function 
that reduces localized tension yet 'weakens' the skull 
overall. Furthermore, peak compressive and shear stresses 
localize in the nasals rather than the fronto-parietal 
region as seen in Allosaurus, offering a reason why 
robusticity is commonplace in tyrannosaurid nasals.

Also discussed online in the Guardian:
Fangs for the memory 

Thursday June 10, 2004
The Guardian <http://www.guardian.co.uk> 

Tyrannosaurus rex slipped away in the late Cretaceous, but 
the predator's jaws are still answering questions. The 
brute had tiny arms but jaws a metre long: 
palaeontologists have puzzled for decades over how it 
hunted and ate. It could never have run down fleet-footed 
prey. And its arms could never have held down a struggling 
triceratops. 
Emily Rayfield, of the University of Cambridge, reports in 
the Royal Society Proceedings B that the predator used 
a "puncture-pull" strategy at the Cretaceous dinner table. 
It began with a bone-crushing bite immediately followed by 
the drawing of teeth through flesh and bone, she thinks. 
The puzzle is that the monster's cranium seemed composed 
of loosely articulated facial bones. Was this a design 
fault, or did it make chewing large victims more 
efficient? 
She used engineering techniques to see whether the skull 
was optimised for the resistance of unco-operative 
mouthfuls ("large bi-directional feeding loads"), if its 
mobile joints were adapted for feeding-induced stress, and 
whether these weakened the skull. The answer: thickened 
nasal bones could manage all the shearing and compression 
necessary, and the sutures between the skull bones 
probably helped to reduce tensile stresses and served as 
shock absorbers when T. rex put the bite on.