cannot be seen with the naked eye. The researchers described theropod phalanges as being "pathognomonic" for stress fractures, this means they are "characteristic and unequivocal diagnostically." Rothschild and the other researchers examined and dismissed other kinds of injury and sickness as causes of the lesions they found on the dinosaurs' bones. Lesions left by stress fractures can be distinguished from osteomyelitis without difficulty because of a lack of bone destruction in stress fracture lesions. They can be distinguished from benign bone tumors like osteoid osteoma by the lack of a sclerotic perimeter. No disturbance of the internal bony architecture of the sort caused by malignant bone tumors was encountered among the stress fracture candidates. No evidence of metabolic disorders like hyperparathyroidism or hyperthyroidism was found in the specimens, either. After examining the bones of many kinds of dinosaur the researchers noted that Allosaurus had a significantly greater number of bulges on the shafts of its hand and foot bones than the tyrannosaur Albertosaurus, or the ostrich dinosaurs Ornithomimus and Archaeornithomimus. Most of the stress fractures observed along the lengths of Allosaurus toe bones were confined to the ends closest to the hind foot, but were spread across all three major digits in "statistically indistinguishable" numbers. Since the lower end of the third metatarsal would have contacted the ground first while a theropod was running it would have borne the most stress and should be most predisposed to develop stress fractures. The lack of such a bias in the examined fossils indicates an origin for the stress fractures from a source other than running. The authors conclude that these fractures occurred during interaction with prey. They suggest that such injuries could occur as a result of the theropod trying to hold struggling prey with its feet. The presence of stress fractures provide evidence for very active predation-based feeding rather than scavenging diets. References External links Overuse injuries Bone fractures Osteopathies de:Knochenbruch#Ermüdungsfraktur