File:Sauropod 2009 neck study.jpg

Summary
Nigersaurus differs from Diplodocus in the angle of the face from the HSCCs and occipital condyle, not in the angle between the HSCCs and the occipital condyle, which is remarkably similar in Camarasaurus, Diplodocus, and Nigersaurus. This suggests that Nigersaurus held its head differently than other sauropods, but not necessarily its neck.

The difference in facial angle between Diplodocus and Nigersaurus is less than 50 degrees, and that some of the head postures in the respective Duijm windows of the two taxa are identical. therefore, it is not certain that Nigersaurus held its head differently than Diplodocus; it is possible that they held their heads at the same angle and that Nigersaurus just carried its HSCCs at a different angle. If that were the case, the neck of Nigersaurus would have been more inclined than that of Diplodocus.

Also note that some of the neck postures allowed by the Duijm window have the anterior cervicals running down, below horizontal, not up. And many of the allowed neck postures for the neosauropods are close to horizontal. So, we were wrong and HSCCs + occipital condyles show that most sauropods held their necks close to level and not strongly elevated after all.

Range of possible habitual head angles in the basal sauropodomorph A. Massospondylus, and the sauropods B. Camarasaurus, C. Diplodocus and D. Nigersaurus. Heads shown with HSSC oriented horizontally, and tilted 30Âº upwards and 20Âº 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).