Biology of the Sauropod Dinosaurs by Klein Nicole.;Sander Martin;Gee Carole T.;Remes Kristian.;

Author:Klein, Nicole.;Sander, Martin;Gee, Carole T.;Remes, Kristian.;
Language: eng
Format: epub
Publisher: Indiana University Press

FIGURE 9.4 SEM micrograph using BSE of secondary osteons in a cross section of an Apatosaurus sp. sample (BYU 601-17328) from the Morrison Formation, USA (femur, 158.0 cm; Klein & Sander 2008). Secondary osteons (one of which is outlined by the dashed line) are delimited by cementing or resorption lines (arrowheads). Characteristic radial cracks (arrows) indicate that this bone was subjected to strain and/or fossilization.

Both the sauropod bone and the cow bone in Fig. 9.3 are dominated by circumferential vascular canals, resulting in a laminar appearance of the bone tissue. However, in the cow bone (Fig. 9.3B), these circumferential canals are additionally connected by radial canals, forming a vascularization pattern called plexiform (see Francillon-Vieillot et al. 1990 for more details). This microstructure has already been noted in other large herbivorous mammals (e.g., Sander & Andrassy 2006) and was previously mentioned by Enlow & Brown (1956, 1958).

This bone tissue is interpreted as resulting from the rapid but normal deposition of new compact bone. Indeed, as a result of the high mass of large mammals and sauropods, their bones must increase in circumference quickly. As in large mammals (de Ricqlès et al. 1991), Haversian bone is also present in long bones of sauropods (Fig. 9.4; Sander 2000; Sander et al., this volume). Haversian bone results from the primary FLB being replaced during remodeling by secondary osteons. These form by erosion of the primary bone tissue and secondary infill by lamellar bone matrix. In long bones, secondary osteons are generally oriented longitudinally.

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