Re: Calculating bite force

[Colin McHenry <cmchenry@westserv.net.au>]

Ville Sinkkonen wrote:

>How are the bite forces of Dinosaurs and extinct mammals calculated?

For theropods, a few ways:
1. measured by simulating a bite based upon fossilised bite marks on 
prey - Erickson et al. 1996 (Measured 13KN for a bite by Tryannosaurus 
on a Triceratops pelvis.

2. calculated by reconstructing musculature in 3D, measuring 
physiological cross sectional area to provide an estimate of muscle 
force, and then calculating bite force from jaw geometry (Rayfield et 
al. 2001).

3. calculated by plotting bite force against body mass for extant 
carnivores and extending the regression line to the body size range for 
large theropods (Meers, 2002 - calculated a bite strength of between 183 
and 235KN).

Note: the disparity between the results of Meers and Erickson is not as 
great as it looks. Erickson et al calculated the bite force at a single 
tooth, whilst Meers calculated it for the entire tooth row (both sides). 
Given its dental morphology, Tyrannosaurus was unlikely to ever bite 
down at just one tooth. As Rayfield (2004) shows, if you take Erickson's 
measurement and extend it across the entire tooth row, allowing for 
geometry, then you get an estimate of 156KN, which is close to the range 
calculated by Meers.

For mammals, the method that has been used is a 2D one based upon 
Thomason, 1991, where the maximum area in the temporal arcade available 
for the temporalis and masseter systems is calculated from photographs, 
and this figure is used to provide an estimate of muscle force and hence 
bite force. Wroe et al (2003) used it to infer bite force in a a range 
of living and extinct mammals. Christiansen & Adolfssen also recently 
published a similar analysis, based upon a modified version of 
Thomason's method.

If you chase this literature, you'll notice Jeff Thomason's name come up 
a lot. He measured bite force in Didelphis (Thomason et al. 1990) and 
used the measured relationship between skull geometry and bite force to 
calculate bite strengths in extant mammals such as lions and wolves. 
Many of the quoted figures for those species come from his 1991 paper - 
as far as I know, they haven't actually been measured in the live 
animals. I think the largest mammal in which bite force has been 
measured is the spotted hyaena (Binder and Van Valkenberg, 2000). In 
reptiles it is the American Alligator (Erickson et al, 2003).

There is also a large body of work on bite force in extant lizards. 
Chase up Tony Herrel's work and you'll come across most of it.

>Is there any estimations on bite force of the great big mesonychids like
>Andrewsarchus or the Creodonts like Hynailouros?
>Ref recomendations are most welcome.

Not that I know of, although they would be interesting.

Cheers
Colin

Refs:

Binder, W. J. & Van Valkenburgh, B. Development of bite strength and 
feeding behaviour in juvenile spotted hyena (Crocuta crocuta), J. Zool. 
Lond. 252, 273-283 (2000)

Christiansen, P. & Adolfssen J.S. Bite forces, canine strength and skull 
allometry in carnivores (Mammalia, Carnivora), J. Zool 266(2) ( 2005).

Erickson, G. M., Van Kirk, S. D., Su, J., Levenston, M. E., Caler, W. E. 
& Carter, D. R. Bite force estimation for Tyrannosaurus rex from 
tooth-marked bones. Nature 382, 706-708 (1996).

Erickson, G. M., Lappin, K. A. and Vliet, K. A. The ontogeny of 
bite-force performance in American alligator (Alligator 
mississippiensis). J. Zool. Lond. 260, 317-327 (2003).

Meers, M. B. Maximum bite force and prey size of Tyrannosaurus rex and 
their relationships to the inference of feeding behaviour. Hist. Biol. 
16, 1-12 (2002).

Rayfield, E. J., Norman, D. B., Horner, C. C., Horner, J. R., Smith, P. 
M., Thomason, J. J., & Upchurch, P. Cranial design and function in a 
large therapod dinosuar. Nature 409, 1033-1037 (2001).

Rayfield, E. J. 2004 Cranial mechanics and feeding in Tyrannosaurus rex. 
Proc. R. Soc. B 271, 1451–1459.

Thomason, J. J. Cranial strength in relation to estimated biting forces 
in some mammals. Can. J. Zool. 69, 2326-2333 (1991).

Thomason, J. J., Russell, A. P. and Morgeli, M. Forces of biting, body 
size, and masticatory muscle tension in the opossum Didelphis 
virginiana. Can. J. Zool. 68, 318-324 (1990).

Wroe, S., McHenry, C., and Thomason, J. (2005). Bite club: Comparative 
bite force in big biting mammals and the prediction of predatory 
behaviour in fossil taxa. Proceedings of the Royal Society of London, 
Series B, 272: 619-625.



Best wishes

Ville Sinkkonen


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Colin McHenry
School of Environmental and Life Sciences (Geology)
University of Newcastle
Callaghan NSW 2308
Australia
Tel: +61 2 4921 5404
Fax: + 61 2 4921 6925

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