We ran a PCA of topological variables by a singular value decomposition of the centered and scaled measures using the function prcomp in the R built-in package stats (52). We used PCA components to test whether the anatomical organization of the appendicular skeleton differed (i) between fins (without digits) and limbs (with digits), (ii) between pectoral and pelvic appendages, and (iii) between extinct and extant taxa. We performed a PERMANOVA over 10,000 permutations using the function adonis in the R package vegan (58). PERMANOVA used a permutation test with pseudo-F ratios on the Euclidean distances of the matrix of PCA components to test the null hypothesis that the centroids and dispersion were equivalent for each group comparison. Rejection of the null hypothesis meant that the network topology differed between the groups compared.