Fig. 9. Physical models of dental plate and jaw kinematics in hagfish and gnathostomes, respectively. (A) Pulley system model for dental plate retraction (left) and protraction (right). (B) Third-order lever system model for jaw adduction (left) and jaw abduction (right) in a large cat (Panthera). Dotted red arrows demonstrate how a jaw can be geared for closing velocity or mechanical advantage by changing relative input lever arm lengths (output lever arm remains unchanged in this example). BP, basal plate; CMJ, craniomandibular joint; DP, dental plate; f, fulcrum; F_i, input force; F_o, output force; JAM, jaw adductor muscle; JDM, jaw depressor muscle; L_i, length of input lever arm; L_o, length of output lever arm; PMG, protractor muscle group; RMG, retractor muscle group.