So obviously, this is a Tyrannosaurus rex. It's so famous I'm afraid I don't really know what else to write about. Oh well, I'll just ramble on about bite forces then.
T. rex has been the focus of many biomechanical studies. Bite force is no exception. However, as much of a celebrity T. rex is, as far as I'm aware, there have only been two studies so far that have attempted to estimate the bite force of T. rex: Erickson et al. (1996) and Meers (2002).
Erickson et al. (1996) had an interesting approach of reproducing bite marks using cast replicas of a T. rex tooth and ramming it into a cow bone. They recorded the forces needed in order to penetrate the bone to different depths. The depths of T. rex bite marks found on a Triceratops ilium was compared to this relationship of puncture depth and forces needed. As a result they found out that a bite force of 6.4 kN were needed in order to to make that bite mark. From the shape and size of the tooth, Erickson et al. (1996) suggested that the bite may have been made from a mid maxillary tooth. So they extrapolated a possible bite force for the posterior-most tooth position. Further, they suggest that up to 30% of the original bite force may have been lost due to several layers of soft tissues that the tooth would have had to penetrate before it reached the bone. In conclusion, they proposed a maximum bite force of 13.4 kN.
Mason Meers (2002) on the other hand employed a much simpler approach. He regressed bite force against body mass and extrapolated the relationship to a 5 tonne T. rex. As a result, his maximum bite force was 183 to 235 kN, an order of magnitude higher than Erickson et al.'s (1996).
So which is closer to the truth?
I would say somewhere in between the two.
Through my own studies, I'm confident to say that Erickson et al.'s (1996) bite force estimate is not really a maximal value. This isn't restricted to just Erickson et al.'s (1996) estimates but for other theropods as well (Rayfield et al. 2001; Mazzetta et al. 2004a, b). With Rayfield et al. (2001) and Mazzetta et al. (2004a, b), their methods in bite force estimation may have the tendency to underestimate. Erickson et al. (1996) on the other hand probably estimated their bite force fairly accurately. The only problem is that the T. rex that produced the bite mark may not have exerted its maximum bite force. The position of the bite on the Triceratops (in the pelvic region) strongly suggests that these bite marks were produced post-mortem and were probably not killing bites but feeding bites. It is unclear just how hard it was biting, but the safe bet is, it was probably just happily munching away at a leisurely (or necessary) bite. I had a chat with Greg Erickson at a conference and he seems to have an opinion along this line as well.
Meers (2002) on the other hand may have overestimated maximum bite force. This is mostly because his slope on the regression equation is closer to 1, or proportional increase of bite force with increasing body mass. So the bigger the animal the stronger the bite. However, my own studies suggest that this slope may actually be significantly lower than 1, so in other words, the bigger the animal, the progressively weaker the bite gets relative to its increase in body mass.
So this puts maximum bite force for T. rex with various body mass estimates at somewhere between 50 to 80 kN.
- Erickson, G. M. , Van Kirk, S. D., Su, J., Levenston, M. E., Caler, W. E. and Carter, D. R. 1996. Bite- force estimation for Tyrannosaurus rex from tooth-marked bones. Nature, 382:706-708.
Gerardo V. MAZZETTA, Adrián P. CISILINO y R. Ernesto BLANCO. 2004a. Distribución de tensiones durante la mordida en la mandíbula de Carnotaurus sastrei Bonaparte, 1985 (Theropoda: Abelisauridae). Ameghiniana 41: 605-617.
Gerardo V. MAZZETTA, R. Ernesto BLANCO y Adrián P. CISILINO. 2004b. Modelización con elementos finitos de un diente referido al género Giganotosaurus Coria y Salgado, 1995 (Theropoda: Carcharodontosauridae). Ameghiniana 41: 619-626.
- Rayfield EJ et al, 2001, Cranial design and function in a large theropod dinosaur, Nature 409: 1033-7