by Aaron G. Filler, MD, PhD
Figure 8-2 Rib Mechanics and Ventilation While Running
A, B – Lizards often have single headed ribs that are pulled dorsally for breathing – a pattern severely disrupted by body undulation in running
C, D – Archosaurs have a more stable front to back rib traverse with two heads. In the upper thorax the axis of rotation is at 45 degrees, but in the lower thorax the ribs rotate on a low axis (as in many mammals) and their coordinated movement is very resistant to body motion.
E – Oxygen consumption goes up with speed, but a mammal can run much faster than a lizard because it can move far more air through its lungs.
A,B - From: Hoffstetter, R. and J.-P. Gasc (1969). Vertebrae and ribs of modern reptiles. Biology of the Reptilia - Morphology A. C. Gans, A. d. A. Bellairs and T. S. Parsons. London, Academic Press. 1: 201-310. Drawings reproduced by permission of J-P Gasc.
C- Redrawn, modified after: (Romer 1956) Romer, A. S. (1956). Osteology of the Reptiles. Chicago, University of Chicago Press.
D – From: Wettstein, O. (1931). Crocodilia. Handbuch der Zoologie. W. Kukenthal and T. Krumbach. Berlin, W. de Gruyter & Co. VII: 236-320. Drawing reproduced by permission of Walter deGruyter Press.
E – Redrawn, modified, after: course outline, personal communication C. Richard Taylor.