Figure 4. Range of possible habitual head angles in the basal sauropodomorph A. Massospondylus, and the sauropods B. Camarasaurus and C. Diplodocus. Heads shown with HSSC oriented horizontally, and tilted 30º upwards and 20º downwards, the range of habitual orientations found for birds by Duijm (1951) . Necks shown in neutral position with respect to heads with horizontal HSCCs. Massospondylus BP/1/4376 after Sues et al. (2004: fig. 1A), Camarasaurus CM 11338 after Gilmore (1925: pl. XVI), Diplodocus USNM 2672 after Hatcher (1901: pl. II).