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Dinosaur stabbing reveals dexterity of stegosaurs, study finds

Oct. 21, 2014
Courtesy of the Geological Society of America
and World Science staff

Artist's reconstruction of stegosaurus. Load­ed with bony pla­tes down their backs, steg­o­saurs, which lived about 150 million to 155 million years ago, are one of the most widely-recognized di­no­saurs. (Image courtesy Wikia.com)


Load­ed with bony pla­tes down their backs, steg­o­saurs, one of the most widely-known di­no­saurs, are some­times por­trayed as lum­ber­ing plant ea­ters.

But they were le­thal fight­ers when nec­es­sary, say sci­en­tists who are re­port­ing new ev­i­dence of a deadly stab wound in­flicted by one of them.

The wound – in a pred­a­to­ry di­no­saur’s pu­bis bone, and in the con­i­cal shape of a steg­o­saur tail spike – would have re­quired great dex­ter­ity to in­flict, ac­cord­ing to the sci­en­tists.

It also, they said, shows clear signs of hav­ing cut short the al­losaur’s life.

“A mas­sive in­fec­tion ate away a baseball-sized sec­tor of the bone” in the pred­a­tor, called an al­lo­saur, said Hous­ton Mu­se­um of Nat­u­ral Sci­ence pa­le­on­tol­ogist Rob­ert Bakker. Bakker and col­leagues pre­sented their find­ings on Tues­day at the meet­ing of the Ge­o­log­i­cal So­ci­e­ty of Amer­i­ca in Van­cou­ver, B.C. 

An allo­saur eyes a stegosaur in this artist's con­cept. Allo­saurus, a rela­tive of the much later T. rex. were one of the most com­mon and vi­cious kill­ers of the late Ju­ras­sic period, when stego­saurus lived. (Image courtesy Wikia.com)


“Probably this in­fec­tion spread up­wards in­to the soft tis­sue at­tached he­re, the thigh mus­cles and ad­ja­cent in­testines and re­pro­duc­tive or­gans.” The lack of any signs of heal­ing strongly sug­gests the in­fec­tion led to death, he added.

Si­m­i­lar wounds are seen in ro­de­o cow­boys or hors­es when they are gored by long­horns, Bakker said. And since large plant-ea­ters – like long­horn cat­tle, rhi­nos and buf­fa­lo – to­day de­fend them­selves with horns, it’s rea­son­a­ble to as­sume spiky her­biv­o­rous di­nos did the same. 

A big dif­fer­ence is that steg­o­saurs wielded their weap­on on their tails rath­er than their heads, he said. Skele­tal ev­i­dence from fos­sil steg­o­saurs sug­gests their tails were more dex­terous than most di­no­saur tails.

“Most di­no­saur tails get stiffer to­wards the end,” he ex­plained. But steg­o­saurs had mas­sive mus­cles at the base of the tails, flex­i­bil­ity and fi­ne mus­cle con­trol all the way to the tip. “The joints of a steg­o­saur tail look like a mon­key’s tail. They were built for three-dimensional com­bat.”

A reconstruction of how a stego­saur might have fa­tal­ly stabbed an allo­saur based on new find­ngs by Robert Bak­ker and col­leagues. (Credit: Rob­ert Bak­ker)


In or­der to de­liv­er the mor­tal wound to the al­lo­saur, he said, a steg­o­saur would have had to sweep its tail un­der the al­lo­saur and twist the tail tip, be­cause nor­mally the spikes point out­ward and back­ward. That would have been well with­in a steg­o­saur’s abil­ity, Bakker said. 

Stegosaurs’ fight­ing style and skill should come as no sur­prise to an­yone fa­mil­iar with the di­no­saur bat­tle scene in the 1940 Dis­ney anima­ted film Fan­ta­sia, said Bakker. The scene shows a beefed up al­lo­saur at­tack­ing a steg­o­saur. The steg­o­saur de­liv­ers a num­ber of well-aimed tail blows at the pred­a­tor, but loses the fight. The Fan­ta­sia steg­o­saur tail dex­ter­ity seems to be accura­te, he said. But he ques­tions the steg­o­saur’s loss in the end—“I think the steg­o­saur threw the fight.” On the oth­er hand, he notes steg­o­saurs had among the small­est brains for its body size of any large an­i­mal, ev­er.


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Loaded with bony plates down their backs, stegosaurs, one of the most widely-known dinosaurs, are sometimes portrayed as lumbering plant eaters. But they were lethal fighters when necessary, say scientists who are reporting new evidence of a deadly stab wound inflicted by one of them in the pubis bone of a predatory dinosaur. The wound – in the conical shape of a stegosaur tail spike – would have required great dexterity to inflict and shows clear signs of having cut short the allosaur’s life, according to the scientists. “A massive infection ate away a baseball-sized sector of the bone” in the predator, called an allosaur, said Houston Museum of Natural Science paleontologist Robert Bakker. Bakker and colleagues presented their findings on Tuesday at the meeting of the Geological Society of America in Vancouver, B.C. “Probably this infection spread upwards into the soft tissue attached here, the thigh muscles and adjacent intestines and reproductive organs.” The lack of any signs of healing strongly suggests the allosaur died from the infection, he added. Similar wounds are seen in rodeo cowboys or horses when they are gored by longhorns, Bakker said. And since large plant-eaters – like longhorn cattle, rhinos and buffalo – today defend themselves with horns, it’s reasonable to assume spiky herbivorous dinos did the same. A big difference is that stegosaurs wielded their weapon on their tails rather than their heads, he said. Skeletal evidence from fossil stegosaurs suggests their tails were more dexterous than most dinosaur tails. “Most dinosaur tails get stiffer towards the end,” he explained. But stegosaurs had massive muscles at the base of the tails, flexibility and fine muscle control all the way to the tip. “The joints of a stegosaur tail look like a monkey’s tail. They were built for 3-dimensional combat.” In order to deliver the mortal wound to the allosaur, he said, a stegosaur would have had to sweep its tail under the allosaur and twist the tail tip, because normally the spikes point outward and backward. That would have been well within a stegosaur’s ability, Bakker said. Stegosaurs’ fighting style and skill should come as no surprise to anyone familiar with the dinosaur battle scene in the 1940 Disney animated film Fantasia, said Bakker. The scene shows a beefed up allosaur attacking a stegosaur. The stegosaur delivers a number of well-aimed tail blows at the predator, but loses the fight. The Fantasia stegosaur tail dexterity seems to be accurate, he said. But he questions the stegosaur’s loss in the end—”I think the stegosaur threw the fight.” On the other hand, he notes stegosaurs had among the smallest brains for its body size of any large animal, ever.