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Re: Dunkleosteus Bite Strength

Richard W. Travsky wrote:

Dunkleosteus terrelli lived 400 million years ago, grew up to 33 feet long and weighed up to four tons. Scientist have known for years that it was a dominant predator, but new embargoed research
Embargoed research, eh?! ;-)

I don't have a subscription to Biology Letters, but the abstract can be viewed under the FirstCite Early Online part of the journal's home page. The authors mention a reconstructed bite force of 5,500N at the rear tooth plates. For comparison, Binder and Van Valkenburgh (2000) obtained a measurement of ~4,500N for a spotted hyaena, and Erickson et al.(2003) measured more than than 9,000N for an American alligator. The baseline maximum bite force estimate (retrieved from trace fossils) for a T. rex is more than 13,000N (Erickson et al, 1996) and the actual maximal bite in this taxon may be magnitudinally larger - Meers (2002/3) estimated it at ~ 183,000 to 235,000N, and Rayfield (2004) gives a figure of 156,000N.

For fish, a measurement of ~1500N from dusky sharks has been quoted in the literature for years - it appears to stem from Snodgrass and Gilbert (1967). Huber et al. (2006) estimated maximal bite force (at the rear of the tooth row) in a 1.5 metre blacktip shark (Carcharhinus limbatus) at 1083N. Assuming that a 1.5m requiem shark weighs no more than 100kg ( an over-estimate?), that means that a placoderm at least 40 times as heavy (using the estimate in the original article) could produce a bite force between 4 and 5 times stronger.

Of course, from the various news headlines you'd have a tough time imagining that placoderms where so inefficent compared to modern sharks. One piece in the Times even gets its decimal point in the wrong place and claims that Dunkleosteus has the largest bite ever measured, "making it almost four times more powerful than /Tyrannosaurus rex"/. Note that this mistake appears to be the newspaper's (the article converts previous bite force estimates of other taxa by 0.1 to convert from Newtons to kg, but for some reason forgets to do this for Dunkleosteus), but it just shows how careful you have to be in feeding your work to the media, especially if primary school arithmetic is involved.


*Feeding mechanics and bite force modelling of the skull of /Dunkleosteus terrelli/, an ancient apex predator*
Philip S.L. Anderson ^AFF1 and Mark W. Westneat ^AFF2

Placoderms are a diverse group of armoured fishes that dominated the aquatic ecosystems of the Devonian Period, 415–360million years ago. The bladed jaws of predators such as /Dunkleosteus/ suggest that these animals were the first vertebrates to use rapid mouth opening and a powerful bite to capture and fragment evasive prey items prior to ingestion. Here, we develop a biomechanical model of force and motion during feeding in /Dunkleosteus terrelli/ that reveals a highly kinetic skull driven by a unique four-bar linkage mechanism. The linkage system has a high-speed transmission for jaw opening, producing a rapid expansion phase similar to modern fishes that use suction during prey capture. Jaw closing muscles power an extraordinarily strong bite, with an estimated maximal bite force of over 4400N at the jaw tip and more than 5300N at the rear dental plates, for a large individual (6m in total length). This bite force capability is the greatest of all living or fossil fishes and is among the most powerful bites in animals.

Cheers Colin

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