The simple regression and the boxplot analysis in T. japonicus (blue), T. lepturus (orange) and T. nanhaiensis (grey) A Total length [D(i,n)] and Preanal length [D(i,m)] B Caudal length [D(m,n)] and Body depth at anus [D(e,f)] C Head depth [D(d,o)] and Orbital length [D(j,k)] and D Head length [D(i,l)] and Head depth [D(d,o)]. The landmarks are illustrated in Fig. 2.