Zusammenfassung

2.3. Tyrannosaurus skeletal geometry acquisition We chose Museum of the Rockies Tyrannosaurus rex specimen MOR 555 because a good cast of this nicely preserved specimen (Fig. 5A) was available next to the University of California Museum of Paleontology (Berkeley, California). This location had enough space for us to set up a three-dimensional (x; y; z) coordinate system for estimating body dimensions. The coordinate system was constructed by laying down a straight 10 m line on the floor near the skeleton, forming the x -axis (craniocaudal; parallel to the body). A total of 67 landmark points on the skeleton (Fig. 5B) were marked to represent the outline of the skeleton from tail to snout (total axial length = 10.8 m). Next, for each point the height (y -axis, with 0 at the floor) was measured using a plumb bob and measuring tape. The coordinates in the x–z (horizontal) plane were measured from the point where the plumb bob contacted the ground when hanging still to the coordinate axes. This simple approach can be used quickly and easily with mounted specimens in most museums. As the skeleton was not oriented in a straight line, the coordinates needed to be straightened out by transforming them so that the midline dorsal points all lay along the same craniocaudal line, which was redefined as the new x -axis. Because the left and right sides of the mounted cast were not symmetrical as in life, we adjusted the z -axis values to be the mean of the measured left/right values. Additionally, as the mouth was open in the cast, we took skull measurements to close the mouth in our model. Limb bone geometry was acquired in a previous study (Hutchinson et al., 2005). The pelvis and hindlimbs were represented in the model as realistic 3D surfaces, each made of several thousand polygons. Joints connecting those bone segments were likewise defined as in the latter study. This 3D limb bone model was connected to the body model by placing its hip joint center at the same location as the centroid of the acetabulum in the mounted ...