Ever since the first proud reconstruction in 1939 Berlin, this sauropod is imagined to have had a near vertical neck, but the fossils provide no basis for such a giraffe-like interpretation. On the contrary, the original steel-engravings and supplemental photographs of the individual vertebrae fossil, when composited to form a vertebral column, shows evidence that the neck was a straight extension of the back as it emerged from the shoulder, with a moderate upward slope due to the tall forelimbs, but a gradual droop out to the head end of this long neck.
Apatosaurus (foreground, center) and Diplodocus look up to Brachiosaurus.
Just like modern giraffes which, contrary to common conception, frequently feed at shoulder height or below, competing with the kudu and gerenuk), Brachiosaurus with its gently down-curved neck appears well designed for "head down" feeding, i.e. from-above approach towards fructifications and other yummy bits. Resist the cultural inertia that derives from decades, indeed generations, of envisioning Brachiosaurus as a Mesozoic giraffe-equivalent, and a refreshingly new, and ecologically plausible view, emerges. It was still a high browser, but with head elevation due its tall forelimbs (which raised both the head and the heart, avoiding the whole issue of blood pressure regulation for an vertical head).
What shape was the neck of Brachiosaurus? Putting aside the popular depictions, such as the seemingly-definitive silhouette illustrations in dinosaur books and even encyclopedias, and the rubbery plastic models sold in museums and go back to the original material. Digital compositing of the individual vertebral illustrations by Janensch of B. brancai reveals a very straight neck (see the longer SII specimen reconstruction from C3 to D2 and the SI series from C2-C7 which came from a smaller individual. Scale bar equals 1 m). Detailed examination shows that the vertebrae are individually spool-shaped, not wedge-shaped as would be required to create the familiar giraffe neck curve associated with Brachiosaurus (scroll from left to right to examine the entire neck).
Brachiosaurus SII cervical series

Cervical vertebrae C10-C13 and dorsal vertebrae D1-D2 were found articulated as a single block (see below, from Janensch). There is no apparent giraffe-like osteological specialization to produce an upturn at the base of the neck. The five vertebrae form a very straight beam as the neck emerged from the shoulders (in fact, D1 is slightly dorsiflected relative to D2). Compare this with four artistic reconstructions (from left to right are details from Czerkas and Czerkas (1991, p. 132), Wilson and Sereno (1998, foldout 1), Janensch (1950b, pl. 8), and Paul (McIntosh et al., 1997 fig. 20.16).

Czerkas and Czerkas illustrated the vertebral column consistently with the osteology (they gave the neck just a few degrees of upturn at the base), and yet Greg Paul depicts those same vertebrae as if they were strongly wedge-shaped, [see colored triangular region], resulting in 68° curvature. It is instructive to compare with the original fossil evidence.

cervicodorsal transition
Many large modern herbivores display a significant arch in support of the gut that hangs below? How arched was the back of Brachiosaurus? Was it straight (as many sauropod dorsal vertebrae would suggest) or strongly arched? I bracket the range of interpretation on this matter. For a shallow arch interpretation, I reconstructed a low arch based on the individual dorsal vertebrae of B. altathorax, which does not form a significant arch in neutral pose. Note the lack of significant keystoning or wedge-shape in the following dorsals of B. altathorax:
To model a high degree of curvature to the back, I use Greg Paul's interpretation for the arch of the back (not the neck!), as it is the most pronounced arch illustrated in the literature (same for his interpretation of the backs of diplodocids, by the way). It is noteworthy that the more arched the back, the less the neck can rise. This is illustrated below, where the same neck is attached to two alternatives for the trunk, where all that varies is the degree of curvature given to the dorsals (scale bar equals 5 m). 
In general across sauropods, there is little consensus of opinion regarding how the pectoral girdles (scapulocoracoids) laid upon the ribcage, i.e. whether they were up high on the ribcage, or down near the ventral margin and keel-like, as well as whether "sub-horizontal" or "sub-vertical" in angulation. So, let's see the range of interpretations that come from two alternatives of dorsal arch ("low arch" and "high arch", the two shown above) and two alternatives of pectoral girdle placement ("high girdles" and "low girdles"). Note that the combination "low arch" + "low girdles" creates the highest head height and "high arch" + "high girdles" creates the lowest head height. The other two alternatives act against each other and create intermediate head heights:  
So, Brachiosaurus, with neck in neutral position, would have held its head 6-7 m above ground level (note the vertical 5 m bar in the middle of the scene below). Diplodocus would have been able to reach to somewhat over 4 m, and Apatosaurus about 6 m. Just as modern giraffes often ventriflex to reach down to feed, the feeding envelope of Brachiosaurus would have had considerable vertical overlap with that of these two sympatric diplodocids.

Copyright © 2011 Kent A. Stevens, University of Oregon Page Counter