Reconstruction of the cervical skeleton posture of <i>Brachiosaurus brancai</i> Janensch, 1914 by an analysis of the intervertebral stress along the neck and a comparison with the results of different approaches

Abstract

The neck posture of Brachiosaurus brancai Janensch, 1914 is reanalysed by employing the Preuschoft method to deduce the pattern of stress in the joints between the vertebral centra along the neck. The cogency of different methods for reconstructing the posture of a long neck, especially the Preuschoft method and approaches that are based on optimal articulation of the neck vertebrae, is discussed critically. The results corroborate the reliability of the Preuschoft method whereas the analyses of recent vertebrates with long necks show that approaches based on optimal articulation of the neck vertebrae are less suited for reconstructing habitual postures of long necks during rest. Such models are better suited for reconstructing the neck posture that was employed during locomotion. With the evidence obtained by different methods a conclusive picture of the neck posture and the feeding strategy of Brachiosaurus brancai can be drawn. The neck appears to have been slightly S-shaped with a ventrally flexed cranial section, an approximately straight middle section, and a dorsally flexed proximal part. In the habitual posture during standing, the angle between the middle section of the neck and the horizontal plane was about 60 or 70. During locomotion the whole neck probably was kept in an lower position with the inclination reduced by approximately 20 compared with the position at rest. During feeding movements of the head relative to the neck and movements in the cranial neck section were performed without much altering the height of the centre of gravity of the neck. With slow dorsoventral movements of the whole neck pronounced changes in the feeding height were possible. Sideways movements of the whole neck were performed by lateral flexion at the base of the neck. According to these findings, the long neck of Brachiosaurus brancai was a means for browsing in great heights as well as a means for increasing the feeding volume without moving the body.

Flexibility along the neck of the ostrich (Struthio camelus) and consequences for the reconstruction of dinosaurs with extreme neck length

“…Raising the head above the shoulders at rest and during locomotion is a common feature of low feeding extant terrestrial vertebrates with long necks, like ostriches and camels. Usually, the neck is kept in a higher position during rest than during locomotion (Dzemski, 2005;Christian and Dzemski, 2007). For sauropods, keeping their long neck always in a very low position, as proposed by Stevens and Parish (1999), is unlikely due to ecological reasons.…”

“…According to Stevens and Parish (1999), in the habitual neck postures of vertebrates with long necks the facets of the prezygapophyses and the postzygapophyses are aligned and centered. Detailed studies by Christian and Dzemski (2007), however, revealed that such ''best fit'' or zygapophyseal alignment postures can deviate considerably from the habitual neck postures at rest, but can resemble the neck postures that are employed during locomotion.…”

“…More vertical postures are preferred by others (Bakker, 1987;Paul, 1987). For Brachiosaurus, the suggested neck posture differs between horizontal and vertical (e.g., Janensch, 1950;Paul, 1988;Frey and Martin, 1997;Christian and Heinrich, 1998;Christian, 2002a,b;Stevens and Parrish, 2005a,b;Christian and Dzemski, 2007). Possibly, different species adopted different neck postures (Dodson, 1990;Upchurch and Barrett, 2000;Christian, 2002a,b).…”

The Case for Natural History

“…In seeking to determine the neck posture of sauropod dinosaurs, researchers must interpret anatomy from an incomplete fossil record. In previous reconstructions of the sauropod body plan, researchers have proposed an upward sloping curve for the neck (see Christian & Dzemski, 2007); others have posited a straight, horizontal or downward curving sloping neck (Stevens & Parrish, 1999). Yet others (Taylor et al, 2009) have argued that sauropods held their necks extended with their heads flexed such that the mid-cervical region was near vertical.…”

CAD assessment of the posture and range of motion of Kentrosaurus aethiopicus Hennig 1915

“…The amount of overlap that remains between the zygapophyses during maximum flexion is hotly debated in the literature (e.g., Parrish 1999, 2005a, b;Christian and Dzemski 2007;Taylor et al 2009). In light of the research of Christian and Dzemski (2007) and Taylor et al (2009) it seems plausible that zygapophysal articulations especially in the neck can move so that overlap of significantly less than 50% occurs.…”