muscles. This pressure would have compressed the muscles' blood vessels and nerves, reducing the range of motion of both the limb's flexor and extensor muscles. This effect would have hindered the M. brachialis, m. brachoradialis, and to a lesser degree the m. biceps brachii to the lesion's position on the humerus. The researchers inferred that the inflammation of the muscles and periosteum would have caused additional complications in the lower region of the fore limb, as well. The lesion would also have caused long-term fasciitis and myosistis. The cumulative effect of these pathological processes would have moderate to severe effects on the ability of the limb to move and "made everyday activities such as foraging for food and escaping predators harder to accomplish." To help determine the cause of the pathology, McWhinney and the other researchers performed a CT scan in 3-mm increments. The CT scan found that the mass had a consistent radiodensity and was separated from the cortex of the bone by a radioleucent line. No evidence was found of stress fracture or infectious processes like osteomyelitis or infectious periostitis. They also ruled out osteochondroma because the axis of the spur is 25° relative to the vertical axis of the humerus, whereas an osteochondroma would have formed at 90° to the axis of the humerus. Other candidates identified by the scientists for the origin of the spur-bearing lesion included: Hypertrophic osteoarthropathy – although this was ruled out by the presence of the spur-like process Osteoid osteoma – but this would not explain the spur or osteoblastic reaction Shin splints or tibial stress syndrome – a possible origin, as many symptoms would be held in common, but shin splints would not explain the spur. Myositis ossificans traumatica (circumscripta) – Possible, but unlikely source. Avulsion injury – McWhinney and the other researchers considered an avulsion injury caused by "repetitive overexertion of the muscles" to be the most likely source for the lesion on the humerus. The researchers believed the lesion to have originated with the avulsion of the m. brachialis causing the formation of "a downward-sloping elliptical mass". The bone spur was caused by an osteoblastic response following a tear at the base of the m. brachioradialis caused by its flexor motion. Paleoecology Habitat The Morrison Formation, situated along the eastern flank of the Rocky Mountains, is home to a fossil-rich stretch of Late Jurassic rock. A large number of