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Kentrosaurus defense (thagomizer) capabilities



From: Ben Creisler
bh480@scn.org

In the new Palaeontologia Electronica
(http://palaeo-electronica.org/2011_2/index.html):


Heinrich Mallison (2011)
Defense capabilities of Kentrosaurus aethiopicus Hennig, 1915 
Palaeontologia Electronica 14(2)
http://palaeo-electronica.org/2011_2/255/255.pdf
ABSTRACT 
Stegosaurs were not built for rapid locomotion. Instead of fleeing from
predators, they probably used their spiked tails as 'thagomizers' for
defense. Kinetic/dynamic modeling in a computer-aided engineering program
allows either using prescribed joint motions to determine joint forces or
torque input models that deliver accelerations and moment of inertia of the
tail tip spikes. Prescribed motion models based on a CAD range of motion
analysis of Kentrosaurus and motions observed in extant long-tailed
reptiles give results consistent with those of models using torque values
calculated from detailed CAD reconstruction of muscle cross sections and
moment arms. Both indicate that the tail of Kentrosaurus was a dangerous
weapon, capable of inflicting painful slashing injuries and debilitating
penetrating trauma, even on large theropods, across a large portion of its
motion range. Continuous rapid motion was at least sufficient for the
spikes to slash open the integument or penetrate soft tissues and fracture
ribs or facial bones, while aimed whiplash blows may have had sufficient
energy to fracture sturdy longbones. 



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