Fig. 7

A part’s eye-view: relations between spring wire conditions. Dashed lines represent coiled parts of the wire that carries the spring function. a Spring/handle unit as in Legget’s Cyprus from 1891 or in tinker traps from the late nineteenth century. b Spring/fixture unit as in Frost (1891). c Spring/striker unit as in “Planchettes,” “Break Back,” “Little Giant” (Tinker 1882), or even in the “wyar Dragin” trap, if the coils of the ends are reduced to one curve each. d Spring/striker unit as in the “Out O’ Sight” (Hooker 1894). As explained in the text, the parsimonious relationship is b–a–c–d. The likely root at c yields a branching phylogeny, which includes a lateral transfer (c→a)