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February 28, 2012

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Trophy for toughest bite may go to T. rex

Feb. 28, 2012
Courtesy of the University of Liverpool
and World Science staff

The ter­ri­fy­ing di­no­saur Ty­ran­no­saur­us rex may have had an even stronger bite than pre­vi­ously rea­lized, sci­en­tists say. A new es­ti­mate would give the beast the dis­tinc­tion of hav­ing the most pow­er­ful bite of any known land an­i­mal, ev­er.

Re­search­ers ar­ti­fi­cially scaled up the skulls of a hu­man, al­li­ga­tor, a ju­ve­nile T. rex, and an­oth­er di­no­saur, Al­lo­saur­us, to the size of an adult T. rex. In each case the chomp­ing forc­es in­creased as ex­pected, but nev­er to the lev­el of the full-grown T. rex.

Image courtesy USGS
Pre­vi­ous stud­ies have es­ti­mat­ed that the great rep­tile’s bite had a force of 8,000 to 13,400 New­tons (1,800 to 3,000 pounds). But giv­en the size of the an­i­mal, thought to weigh more than 6,000 kg (6.6 tons), some re­search­ers sus­pected its bite may have been stronger. 

In the new study, uni­vers­ity of Liv­er­pool sci­en­tists de­vel­oped a com­put­er mod­el to rev­erse-eng­i­n­eer the an­i­mal’s bite. Bite force is largely de­ter­mined by jaw mus­cle size. The re­search­ers com­put­er-tested a range of mus­cle val­ues for T. rex, as it’s not known ex­actly what its mus­cles were like. Even with er­ror mar­gins fac­tored in, the meth­od still point­ed to a bite force at least 50 per­cent high­er than the pre­vi­ous, high-end es­ti­mates. The team al­so found that as young T. rex grew, the bite force grew faster than its weight—sug­gesting the beast might have changed its feed­ing be­hav­ior as it de­vel­oped.

“The pow­er of the T. rex jaw has been a much de­bat­ed top­ic,” said bi­ol­o­gist Karl Bates, a mem­ber of the re­search team. “Sci­en­tists only have the ske­l­e­ton to work with, as mus­cle does not sur­vive with the fos­sil, so we of­ten have to rely on sta­tis­ti­cal anal­y­sis or qual­i­ta­tive com­par­isons to liv­ing an­i­mals, which dif­fer greatly in size and shape.”

Bates ex­plained that “we took what we knew about T. rex from its ske­l­e­ton and built a com­put­er mod­el that in­cor­po­rat­ed the ma­jor ana­tom­i­cal and phys­i­o­log­i­cal fac­tors that de­ter­mine bite per­for­mance. We then asked the com­put­er mod­el to pro­duce a bite so that we could meas­ure the speed and force of it di­rect­ly. We com­pared this to oth­er an­i­mals of smaller body mass and al­so scaled up smaller an­i­mals to the size of T. rex to com­pare how pow­er­ful it was in rel­a­tive terms.

“Our re­sults show that the T. rex had an ex­tremely pow­er­ful bite, mak­ing it one of the most dan­ger­ous preda­tors to have roamed our plan­et. Its un­ique mus­cu­loskele­tal sys­tem will con­tin­ue to fas­ci­nate sci­en­tists for years to come.” The re­search, in col­la­bora­t­ion with the Uni­vers­ity of Man­ches­ter, is pub­lished in the jour­nal Bi­ol­o­gy Let­ters.

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The terrifying dinosaur Tyrannosaurus rex may have had an even stronger bite than previously estimated, scientists say. The new estimates would give the beast the distinction of having the most powerful bite of any land animal ever. Researchers artificially scaled up the skulls of a human, alligator, a juvenile T. rex, and another dinosaur, Allosaurus, to the size of an adult T. rex. In each case the chomping forces increased as expected, but never to the level of the adult T. rex. Previous studies have estimated that the great reptile’s bite had a force of 8,000 to 13,400 Newtons (1,800 to 3,000 pounds). But given the size of the animal, thought to weigh more than 6000 kg (6.6 tons), some researchers suspected its bite may have been stronger. University of Liverpool scientists developed a computer model to reverse-engineer the animal’s bite. Bite force is largely determined by jaw muscle size. The researchers computer-tested a range of muscle values for T. rex, as it’s not known exactly what its muscles were like. Even with error margins factored in, the method still pointed to a bite force at least 50 percent higher than the previous, high-end estimates. The team also found that as young T. rex grew, the bite force grew faster than its weight—suggesting the beast might have changed its feeding behaviour as it developed. “The power of the T. rex jaw has been a much debated topic,” said biologist Karl Bates, a member of the resarch team. “Scientists only have the skeleton to work with, as muscle does not survive with the fossil, so we often have to rely on statistical analysis or qualitative comparisons to living animals, which differ greatly in size and shape.” Bates explained that “we took what we knew about T. rex from its skeleton and built a computer model that incorporated the major anatomical and physiological factors that determine bite performance. We then asked the computer model to produce a bite so that we could measure the speed and force of it directly. We compared this to other animals of smaller body mass and also scaled up smaller animals to the size of T. rex to compare how powerful it was in relative terms. “Our results show that the T. rex had an extremely powerful bite, making it one of the most dangerous predators to have roamed our planet. Its unique musculoskeletal system will continue to fascinate scientists for years to come.” The research, in collaboration with the University of Manchester, is published in the journal Biology Letters.