by Aaron G. Filler, MD, PhD
Figure 8-4 Bipedalism and Running in Diapsids
A,B, - To move more air, some lizards run bipedally so they can suppress undulation in their anterior body .
C,D – early dinosaurs were small and ran bipedally, probably for the same reason .
E – Our understanding of dinosaur posture and locomotion has advanced steadily.
F – When a dinosaur holds its body horizontal, the vertebrae interlock to provide a rigid beam so the ribs will swing in a coherent fashion .
G – Some types of dinosaurs had ossified (bony) ligaments to hold the spine stiff .
A/B - From: Irschick, D. J. and B. C. Jayne (1999). Comparative three-dimensional kinematics of the hindlimb for high-speed bipedal and quadrupedal locomotion of lizards. Journal of Experimental Biology 202 (Pt 9): 1047-65. Images reproduced by permission of The Company of Biologists Ltd.
C/D - From: Heilmann, G. (1927). The Origin of Birds. New York, D. Appleton and company.
E - From: McLoughlin, J. C. (1979). Archosauria, A New Look at the Old Dinosaur. New York, Viking Press. Copyright © 1979 by John C. McLoughlin. Drawings reproduced by permission of Viking Penguin, a division of Penguin Group (USA) Inc.
F - From: Janensch, W. (1950). Die Wirbelsäule von Brachiosaurus brancai. Palaeontographica Supplement VII, Erste Reile, II: 27-93. by permission of E. Schweizerbart'sche Verlagsbuchhandlung (Nägele u. Obermiller), Science Publisher, http://www.schweizerbart.de/j/palaeontographica/E-palaeontographica.html
G - Redrawn, modified by M. Rivera and AGF, after: Bakker, R. T. (1993). The Dinosaur Heresies : New Theories Unlocking the Mystery of the Dinosaurs and Their Extinction. New York, Kensington Publishing Co.