Sauropod neck posture

A 2000 study conducted by Roger Seymour and Harvey Lillywhite found that the blood pressure needed to reach the head with an upright neck would be 700 millimetres of mercury (28 inHg), interpreted as fatal to an endotherm, or highly dangerous to an ectotherm, even with adequate heart musculature.

[8] The above work summarily dismisses the hypothesis of secondary hearts in the neck[9] as evolutionarily implausible, assuming arterial valves could have no role without associated musculature.

Michael P. Taylor et al. compared the neck posture of sauropods to that of extant reptiles and other tetrapods, finding these animals' habitual poses to be entirely different from the assumptions of Stevens and Parrish.

Taylor et al. find the ONP to be, not the actual habitual pose of any examined animal, but an arbitrarily chosen midpoint between the two structural extremes of bone placement.

The study reconstructed the skeletons of Diplodocus, Camarasaurus, and the titanosaur Opisthocoelicaudia, all known from a complete shoulder girdle, with the correct orientation of the scapulocoracoids.

[12][13] A juvenile Camarasaurus found by Gilmore was originally described as having the scapulocoracoid in "just the right place", but with it oriented at an angle of 45°, Schwartz et al. criticized the stance.

The skeleton found by Schwartz et al. with the angle of the scapulocoracoid is similar to previous reconstruction of the genus by Osborn and Mook, and Jensen.

[11] Despite skepticism, Euhelopus and Brachiosaurus have been found on anatomical evidence to have held their necks at a vertical angle, which has been treated as impossible for sauropods.

Studies have concluded that the blood pressure and energy spent holding necks erect would have been too great to survive; yet Euhelopus and Brachiosaurus, at least, did so anyhow.

Elongated cervical ribs are skeletal evidence for a strong core to support the neck and limit its movement when walking.