R e s e a r c h

Reconstruction of the neck posture and neck utilisation in sauropods and prosauropods, and its relevance for body design

The neck posture is a crucial feature in sauropods and prosauropods affecting biomechanics, physiology, ecology, and evolution of these animals. For various sauropods and some prosauropods, the neck posture is reconstructed using the method developed by Preuschoft (1976) which is based on a comparison of stress values in the intervertebral discs along the vertebral column. The mass distribution along the neck is estimated in different ways, assuming different degrees of pneumatisation and different amounts of soft tissue. For each specimen, the range of possible stress values in the intervertebral discs along the neck is tested for different neck postures in order to find habitual postures which are characterised by more or less constant stress values along the neck. In order to reconstruct neck movements, lever arms of muscles, tendons, and ligaments and the articulation of adjacent neck vertebrae are analysed in selected specimens.

For comparison, neck anatomy and neck movements are being studied in long-necked vertebrates like giraffes, camels, and some birds (e.g., ostriches). Neck mechanics will be related to the overall construction of the dinosaurs studied. For this purpose, especially the dimensions of limb bones, the tail length, and the structure of the pelvis and the pectoral girdle will be analysed in some dinosaurs with different neck postures.

Papers (as pdf)

Funktionsmorphologische Betrachtungen

der Halsstellung bei Zoogiraffen (german edition)

(1.2mb)

Abstract:

In three german zoos neck positions of giraffes were taken during different activities like feeding, standing and moving forward. The range of dorsoventral neck movements reached from 110° above to -70° below the horizontal plain. The maximum lateral movement of the necks was 200° to each side. During standing, the neck was frequently kept in a position between 45° and 65° above the horizontal plain for long time intervals. It appears that the neck could be kept in this range of inclination with little effort. This is possibly due to stress in the dorsal neck ligaments like the ligamentum nuchea. During feeding, the neck was sometimes lowered below the horizontal plain. Such position were kept for short times intervals only, indicating that muscle force was neccessary to act against the stress in dorsal strucutres. During locomotion, the neck was lowered to a position between 25° and 45° above the horizontal plain. Possibly high stress in the dorsal neck ligaments is necessary to contract against high and variable force acting in the neck during locomotion. Due the different heights of the feeding cages in the different zoos, the average neck position during feeding varried among the zoos. This had no effect on the average neck position during other activities.The advantage of a long neck in giraffes appears to be not only the accessibility of resources high above the gound, but also the large fedding volumen that can be reached without much effort.

Keywords: neck position, giraffe, sauropod, biomechanic, functional morphology, evolution

Published in:

Dzemski, Gordon (2005): Funktionsmorphologische Betrachtungen der Halsstellung bei Zoogiraffen. Der Zoologische Garten. N. F. 75, Seite 189 – 201.