The sandfish lizard and the numerical simulation.

<p>A: A sandfish lizard (<i>Scincus scincus</i>) resting on 3 mm diameter glass particles. B: A simulated sandfish with a uniform body resting on simulated 3 mm particles. <i>A</i> and λ represent the amplitude and the wavelength of the single period sinusoidal traveling wave. Dashed purple line shows the outline of a tapered body. C: The elements of the sandfish model in the Working Model multibody simulation environment. The cuboid body segments are connected by actuators and <i>β</i> is the angle between two segments. D: Diagram of the empirical force relations used for particle interaction. The normal (<i>Fn</i>) and tangential (<i>Fs</i>) forces between two particles are calculated based on the relative speed <i>v</i> = <i>v</i>1−<i>v</i>2 and the virtual overlap <i>δ</i> between these two particles. Panels B, C, and D are reproduced from <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1002810#pcbi.1002810-Maladen3" target="_blank">[21]</a>.