The joints of some arthropods have two degrees of bending freedom (up-down and left-right) thanks to two 1-degree bending joints found at right angles to each other.


"Bending both up-down and left-right…Arthropods gain two degrees of bending freedom by putting two 1-degree bending joints next to each other, each oriented at a right angle to the other…The classic work on such cases was done by S.M. Manton, in the 1950s and 1960s; as put, with a long list of references, by Wainwright et al. (1976), 'The accounts of her researches in this field constitute a monument in the study of mechanical design of the most mechanically diverse group of organisms that have ever lived.'" (Vogel 2003:403)

Comparative Biomechanics: Life's Physical World, Second EditionPrinceton University PressFebruary 28, 2017
Steven Vogel