Bayesian inference of partial (domains 1–3) 28S rDNA sequences of a reduced taxon set of proteocephalideans (unstable taxa Sciadocephalus megalodiscus, Vermaia pseudotropii and Manaosia bracodemoca have been removed) performed using MrBayes version 3.2 using the GTR + I + G model of sequence evolution. Two parallel runs were performed for 10,000,000 generations; 4,000,000 generations were discarded as burnin. Branches with posterior probability (pp) support below 95% are collapsed; pp are indicated below branches. Asterisks mark new sequences. Red letters A to P refer to specific nodes discussed in the text. Red circles refer to the acquisition of “Type 2” uterus development; purple circles: acquisition of “intermediate type” uterus development; yellow circle: uterus development unknown (see Discussion). A mute phylogram of the same tree is inserted and the long branch leading to Sandonella sandoni is marked with an asterisk.