Comparative studies of body mass, cortical bone geometry, and preferred crystallographic orientation (texture) of bone mineral in an ontogenetic series of the sauropod, Apatosaurus sp., and recent animals are reported. The cortical bone geometry shows that sauropods have an expansion of the cortical thickness as a result of their heavier mass. It is shown that a universal power-law relationship connects body mass to bone length, suggesting the validity of Wolff's law for sauropods. Moreover, sauropod and mammalian bones seem to be exposed to the same compressive bone stress. X-ray texture measurements of long bones were used to study the orientation of carbonated hydroxyapatite (HA) crystals. All bones investigated showed a 001-fibre texture, in which the c-axis of the HA crystals is oriented along the bone axis. Texture strength (defined by the alignment of HA crystals) appears to be of only minor importance regarding the mechanical strength and seems to be influenced by the loading mode of the bone. (C) 2014 The Linnean Society of London.