Fig. 10 in An integrated approach to understanding the role of the long neck in plesiosaurs

Fig. 10. The range of movement available to the plesiosaur neck. A. Sketch of living or plesiosaur illustrating the three senses of motion (roll, pitch, and yaw) potentially available at each vertebral junction. B. Enhanced dorsoventral movement produced by the laterally expanded articular face of a post-axial cervical vertebrae. Note how more of the same length arrows project dorsoventrally than laterally, indicating greater potential for flexibility in dorsoventral pitch that lateral yaw. C. The potential range of movement available at a plesiosaur posterior-cervical vertebra, where freedom of movement is greatest dorsolaterally between the neural spine and cervical ribs, or ventrally between the cervical ribs, in the same way a tripod is more likely to fall over between two of the legs than over one of them. Once the anatomy of the zygapophyses, neural spines, and cervical ribs are taken into account, the movement is restricted to the ventral direction. Images from: C, Andrews (1910: pl. 7: 4); A, B, LFN drawings.