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Kung Fu Stegosaur

For Immediate Release
21 October 2014
GSA Release No. 14-77
Christa Stratton
Director of Education, Communication, & Outreach

during the meeting

19-22 Oct. 2014
Photos Below
14-77_photoC AlloStegoStabSmall

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Boulder, CO, USA — Stegosaurs might be portrayed as lumbering plant eaters, but they were lethal fighters when necessary, according to paleontologists who have uncovered new evidence of a casualty of stegosaurian combat. The evidence is a fatal stab wound in the pubis bone of a predatory allosaur. 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.

“A massive infection ate away a baseball-sized sector of the bone,” reports Houston Museum of Natural Science paleontologist Robert Bakker and his colleagues, who present a poster on the discovery 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.

Similar wounds are seen in rodeo cowboys or horses when they are gored by longhorns, Bakker said. And since large herbivores – 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. Skeletal evidence from fossil stegosaurs suggests their tails were more dextrous than most dinosaur tails.

“They have no locking joints, even in the tail,” Bakker explained. “Most dinosaur tails get stiffer towards the end.” But stegosaurs had massive muscles at the base of the tails, flexibility and fine muscle control all the way to the tail 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, 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 the ability of a stegosaur, Bakker said. 

The fighting style and skill of stegosaurs should come as no surprise to anyone familiar with the dinosaur battle scene in the 1940 Disney animated film Fantasia, said Bakker. That segment of the movie 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 appears to be accurate, he said. But he questions the stegosaur's loss in the end. “I think the stegosaur threw the fight,” he said. On the other hand, he points out stegosaurs had among the smallest brains for its body size of any large animal, ever.

Stegosaurian Martial Arts: A Jurassic Carnivore Stabbed by a Tail Spike, Evidence for Dynamic Interactions between a Live Herbivore and a Live Predator
Session No. 221 – Booth #247
Paleontology: New Discoveries in Vertebrate Trace and Body Fossils (Posters)

Robert T. Bakker
Department of Paleontology, Houston Museum of Natural Science, Houston, TX
Phone: 832-584-5051

Tuesday, 21 October 2014: 9:00 AM-6:30 PM
Vancouver Convention Centre-West Exhibition Hall C

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The Geological Society of America, founded in 1888, is a scientific society with more than 26,500 members from academia, government, and industry in more than 100 countries. Through its meetings, publications, and programs, GSA enhances the professional growth of its members and promotes the geosciences in the service of humankind. Headquartered in Boulder, Colorado, GSA encourages cooperative research among earth, life, planetary, and social scientists, fosters public dialogue on geoscience issues, and supports all levels of earth science education.

IMAGES & CAPTIONS: (Click on the images for high-resolution versions)

14-77-photoD AlloStegStrkeHoriz14-77_photoC AlloStegoStabSmall<< 14-77_photoC  AlloStegoStabSmall
The wound found in the allosaur fits well with what would result from a stegosaur striking under and upwards with its spiked tail. Fossil's of contemporaneous stegosaurs appear to have had unusually flexible and agile tails. Credit: Robert Bakker


14-77-photoD AlloStegStrkeHoriz  >>
The size and conical shape of the allosaur bone injury closely fits that of the spikes on a stegosaur tail. The stegosaur wouldhave had to wield its tale with great skill to make the deadly blow. Credit: Robert Bakker

14-77-photoE AlloAbcessLabel


<< 14-77-photoE AlloAbcessLabel
The stegosaur tail spike appears to have entered the allosaur's publis from below and passed all the way through the bone. The wound then led to infection and an abscess that eventually spread and killed the allosaur. Credit: Robert Bakker.