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Evidence for Predator- Prey Relationships Examples for Allosaurus and Stegosaurus

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Unequivocal evidence of predator-prey relationships in the vertebrate fossil record is rare owing to the vagaries of preservation and the difficulties of interpretation. Occasionally, commutative evidence may be found that strongly implies such a relationship. Several pathological, contemporaneous specimens of the large theropod Allosaurus and the large stegosaur Stegosaurus from the Upper Jurassic Morrison Formation suggest an antagonistic relationship that is most likely between predator and prey. The specimens include a Stegosaurus cervical plate with a bite pattern that matches that of an Allosaurus mouth, an Allosaurus anterior caudal with a partially healed wound congruent with what a Stegosaurus tail-spike puncture would be expected to cause, and Stegosaurus spikes with broken tips exhibiting remodeling of the bone, implying that the spikes were broken well before death. In this study, the spike force levels generated by the tail motion of Stegosaurus are estimated and compared to the stress levels likely to fracture the spikes. Tail spikes were susceptible to failure when imposed stresses exceeded their bending strength at impact or when shear or torsion loads exceeded spike strength. Estimates of spike penetration performance below load-induced failure levels at plausible spike-strike speeds and geometries suggest that life-threatening wounds could have 325 been imposed on a fully grown Allosaurus, as well as other predators and even conspecifics. The spike-bearing tail of Stegosaurus thus appears to have been a formidable weapon for both offensive and defensive purposes and may have contributed to the prolonged, widespread success of the stegosaurid taxon in the presence of the allosaurid one.
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... Furthermore, braincase endocasts of the stegosauruids Stegosaurus 11 and Kentrosaurus 12 share slight lateral www.nature.com/scientificreports/ eminences, which have been identified as floccular recesses (however, not present in all Stegosaurus specimens 14 ), and both taxa have spiked tails, which were very likely proper defensive means 49,50 . Arbour and Currie 2 reported a stepwise acquisition of clubbed tails in ankylosaurids, leading to a handle first (interlocking vertebrae produce a stiffened tail) and a knob second (fusion of distal-most osteoderms) model. ...
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