4 November 2015 at 20:33:58 MST
Day number 4 showcases one of my favorite dinosaurs, Ornitholestes! It has been alerted to the sound of a larger animal nearby as it forages.
"A biomechanical study conducted by Phil Senter (2006) used articulated casts of the Ornitholestes type specimen's right forelimb to determine its range of motion. Senter found that the antebrachium (forearm) could swing freely within a 95° range. When flexed (bent inward) at the elbow joint to the maximum possible extent, the humerus (upper arm bone) and radius (a lower arm bone) formed a 53° angle. The ability of Ornitholestes to bend the forearm to an angle significantly more acute than 90° is characteristic of Maniraptoriformes, but absent in more primitive theropods such as Coelophysis and Allosaurus.
Even when fully extended (straightened) at the elbow, the forearm did not form a straight angle, falling short of this by 22°. Pronation (twisting to make the palmar side of the hand face downwards) of the forearm was impossible, because the radius and ulna lacked rolling surfaces, meaning the forearm was in a permanent state of supination.
When Ornitholestes bent its elbows, this would cause the forearms to move inward, towards its midline. It may have used that ability to grasp prey with both hands simultaneously." - Wikipedia
Art © 2015 Stephanie Dziezyk.