Studying Function and Behavior in the Fossil Record
Figure 2
Finite element analysis of the skull of T. rex.
The skull of T. rex is perhaps one of the most talked about fossils of all time, coming as it does from perhaps the most fearsome, and certainly the largest, terrestrial predator that ever lived. But the anatomy of the skull reveals a paradox; while T. rex is assumed to have been capable of producing extremely powerful bite forces, the skull bones are quite loosely articulated. Does this mean that the skull would have expanded and distorted if its owner bit too hard into a Triceratops carcass, or did T. rex have to control its bloodthirsty efforts? Emily Rayfield [19] studied all the available skulls (A) and constructed a mesh of triangular elements, small triangular or cuboid cells that define the 3-D shape in preparation for engineering analysis. The technique used is FEA, a numerical method worked out in the 1940s to study the physical properties of buildings. In Rayfield's FEA model of the T. rex skull, modeled bite forces of 31,000–78,060 newtons were applied to individual teeth, and the distortion of the element mesh observed (B). The bite forces had been taken from calculations by other paleobiologists, and from observations of tooth puncture marks (a piece of bone bitten by T. rex showed the tooth had penetrated the bone to a depth of 11.5 mm, equivalent to a force of 13,400 newtons, or about one-and-a-half tons). Rayfield's results show that the skull is equally adapted to resist biting or tearing forces and therefore the classic “puncture-pull” feeding hypothesis, in which T. rex bites into flesh and tears back, is well supported. Major stresses of biting acted through the pillar-like parts of the skull and the nasal bones on top of the snout, and the loose connections between the bones in the cheek region allowed small movements during the bite, acting as “shock absorbers” to protect other skull structures. (Image Credit: Emily Rayfield)