Allosaurus fragilis was the dominant apex carnivore of the Morrison Formation ecosystem across western North America during the Late Jurassic Period (~155 to 145 million years ago). Reaching lengths between 8.5 and 9.7 meters and adult weights of 1,500 to 2,500 kg, Allosaurus represents the archetypal member of the Theropoda lineage Allosauroidea.
Locomotion and Biomechanics:
Biomechanical limb evaluations indicate that Allosaurus had relatively long hindlimbs and gracile tibia-femur proportions compared to tyrannosaurids, indicating capable cursorial locomotion. Finite element simulations and muscle modeling suggest estimated running speeds between 25 and 35 km/h (model-dependent), although velocity was constrained by body mass and joint stress thresholds. Its skull was uniquely engineered: while static bite force was modest, its cranial architecture and neck musculature were adapted for high-impact slashing strikes against large prey.
Scientific Significance:
Allosaurus is one of the most thoroughly analyzed theropods in vertebrate paleontology, providing invaluable baselines for population biology, predator-prey dynamics, and paleopathology. Clear skeletal evidence of violent trophic interactions exists, including an Allosaurus cervical vertebra pierced by a Stegosaurus tail spike and healed Allosaurus bite marks on sauropod vertebrae.
