Fig. 3. Evidence from empirical data that conditions promoting systematic error correlate with support for monophyletic Deuterostomia.

(A) Bar chart showing the average branch lengths within Chordata, Xenambulacraria, Protostomia, and from the outgroup taxa to bilaterian root. Datasets with the greatest branch length heterogeneity (Rouse, Cannon, and Laumer) support deuterostome monophyly. (B) Box plot showing the lengths of branches leading to the Deuterostomia, Protostomia, and from the outgroups to Bilateria estimated using different models of evolution with increasing fit to data. With improving model fit, the estimated length of the deuterostome branch decreases, and estimated protostome and outgroup branch lengths increase—conditions that could reduce LBA between protostome and outgroups.