Nicholls and Russell made the novel argument that theropods had highly mobile shoulder blades, walking dinosaur csotume like those of the pec’uliar chameleon lizards and many mammals.ts While it is quite true that quadrupedal dinosaurs were like this,16 most protobirds were not-their big birdlike furculas and coracoids tightly interlocked and attached in some cases, to big sternal plates. In most theropods the coracoid may have been able to glide back and forth to some degree in the sternal groove-but probably less than in quadrupedal species, and not enough for artists to notice.
In quadrupedal dinosaurs, including the early predatory protodinosaurs, the shoulder joint faced downward. Realistic animatronic dinosaur The forelimb could then work in a nearly vertical plane beneath the body.’7 As the bipedal predatory dinosaurs needed the forelimbs for other purposes-ones that required them to reach further out and in front of the body-their shoulder joint faced more outward.In many predaceous dinosaurs the elbow’s twin, bulbous joints for the lower arm bones were equal in size, making it the simple kind of hinge it is in most animals. lifelike animatronic dinosaur The wrist bones were also most flexible in an up-and-down direction, like our wrists. In many protobirds, however, the elbow’s outer joint bulb was enlarged, and one of the wrist bones became alarge, semicircular pulley upon which the hand could pivot through a large sideways arc. Next time you eat chicken wings, notice that birds still have this kind of “pushpull” elbow-wrist system, which is what folds the forelimb up so neatly €rgure 4-Ll). Protobirds such asArchceopteryx and Velociraptor could fold their arms this way, although not as well as birds. The early herrerasaurs may also have had a less developed version of this svstem.