Table S1 Inter-breed morphological variation is resolved into nine terms.

breed / Xscale / Yscale / Zscale / C1BDS / C3BDS / C1MSH / C1KB / C1X2S / C1Z3S
Afghan hound / 0.925 / 0.980 / 1.104 / 0.161 / 0.798 / -0.036 / 0.109 / 0.505 / -0.334
Airedale terrier / 0.936 / 0.965 / 0.983 / -0.412 / 0.319 / 0.032 / 0.184 / -0.862 / -0.793
Borzoi / 0.857 / 0.941 / 1.029 / -0.200 / 0.800 / -0.524 / 0.143 / -0.268 / -1.446
boxer / 1.027 / 1.020 / 1.083 / 0.309 / 0.791 / 0.012 / -0.075 / -0.559 / 2.212
bullterrier / 0.957 / 0.972 / 1.006 / -0.016 / 0.467 / -0.032 / 0.272 / -0.671 / 0.594
coyote / 0.919 / 0.833 / 0.907 / -0.291 / 0.322 / -0.351 / 0.109 / 0.630 / -0.870
English bulldog / 1.230 / 1.007 / 0.721 / 0.429 / 0.800 / -0.939 / -0.332 / -1.334 / 0.408
English setter / 0.991 / 1.107 / 1.109 / -0.297 / 0.549 / -0.008 / 0.041 / 1.170 / -0.232
fox terrier / 0.748 / 0.765 / 0.757 / 0.000 / 0.785 / -0.091 / 0.162 / 0.074 / -0.668
greyhound / 1.021 / 1.041 / 1.060 / -0.319 / 0.305 / 0.199 / 0.105 / 0.406 / -0.988
mastiff / 1.057 / 1.265 / 1.161 / -0.395 / 0.655 / -0.030 / -0.213 / -2.098 / 0.353
mongrel / 0.765 / 0.745 / 0.597 / 0.245 / 0.680 / 0.306 / -0.161 / 1.052 / -0.258
NGSD / 0.898 / 0.752 / 0.849 / 0.000 / 0.799 / -0.160 / 0.110 / 1.332 / 0.341
pharaoh hound / 0.812 / 0.908 / 0.971 / 0.197 / 0.781 / -0.354 / 0.018 / -0.568 / -0.608
pit bull / 1.133 / 1.069 / 1.066 / -0.015 / 0.680 / -0.015 / -0.038 / -0.272 / 0.325
Rhodesian ridge / 1.088 / 1.002 / 1.011 / -0.461 / 0.574 / -0.205 / 0.007 / -0.850 / -1.162
collie / 0.822 / 0.841 / 0.911 / -0.500 / 0.302 / 0.049 / 0.356 / -0.638 / -1.133
saluki / 0.895 / 0.854 / 0.908 / -0.152 / 0.598 / -0.198 / 0.125 / 0.653 / -0.701
Skye terrier / 0.732 / 0.687 / 0.650 / 0.290 / 0.800 / 0.397 / 0.008 / 1.057 / 0.346
standard poodle / 0.861 / 0.914 / 0.911 / -0.424 / 0.576 / 0.215 / 0.078 / -0.116 / -0.553
su20792 / 0.800 / 0.752 / 0.691 / -0.214 / 0.800 / 0.266 / 0.004 / 0.839 / 0.097
su20794 / 0.749 / 0.721 / 0.625 / 0.500 / 0.749 / 0.414 / 0.018 / 1.051 / 0.717
su20795 / 0.835 / 0.750 / 0.663 / -0.003 / 0.800 / 0.538 / -0.046 / 1.111 / 0.728
su20796 / 0.727 / 0.725 / 0.670 / 0.232 / 0.800 / 0.004 / 0.101 / 1.436 / 0.071
su20797 / 0.742 / 0.774 / 0.643 / 0.428 / 0.799 / 0.304 / -0.114 / 0.962 / -0.608
su20838 / 0.927 / 0.911 / 0.916 / 0.243 / 0.800 / 0.157 / -0.030 / -0.115 / -0.088
su20839 / 1.000 / 1.000 / 1.000 / 0.000 / 0.800 / 0.000 / 0.000 / 0.000 / 0.000
vizsla / 1.157 / 0.987 / 0.987 / 0.242 / 0.800 / 0.261 / 0.012 / 1.399 / -0.616
Pem Wlsh corgi / 0.752 / 0.815 / 0.690 / -0.282 / 0.523 / 0.109 / 0.105 / -0.521 / -0.361
gray wolf / 1.116 / 1.010 / 1.188 / -0.496 / 0.304 / -0.616 / 0.057 / -0.969 / -1.264
toy poodle / 0.678 / 0.674 / 0.644 / -0.167 / 0.626 / 0.402 / 0.008 / 1.205 / 0.167

Xscale, Yscale, & Zscale are terms for linear rescaling of the skull in lateral, dorso-ventral, and rostro-caudal axes, respectively (see Fig. 1 for axis definitions).

C1BDS, primary coefficient for lateral flare of ventral aspect of skull (Fig. 3 eq. 4; C2 static).

C3BDS, secondary coefficient for the inflection point along the A/P axis of lateral flare of ventral aspect of skull (Fig. 3 eq. 4); constrained to range of 0.3 – 0.8.

C1MSH, coefficient for lateral flare of dorsal aspect of skull (Fig. 3 eq. 3).

C1KB, coefficient for the degree of dorsal-ventral snout bend (Fig. 3 eq. 5).

C1X2S, coefficient for lateral snout distortion (Fig. 3 eq. 2; C2 & C3 static).

C1Z3S, coefficient for A-P snout distortion (Fig. 3 eq. 1; C2 & C3 static).