Aquatic environment (freshwater/marine) mapped on to the fully resolved phylogeny inferred from the concatenated 28S and COI sequences. Bold letter indicates genus according to Petrochenko’s (1956) scheme: E, Echinorhynchus; M, Metechinorhynchus; P, Pseudoechinorhynchus. The bar chart shows the mean number of paired cement glands in each taxon. Data for Echinorhynchus spp. are from Table 2. Since the particular cement gland pattern exhibited by each of the species of the E. gadi group is not known, data from a collection of worms determined as E. gadi have been used for E. gadi spp. I & III (the bars for these species are shaded grey rather than black, to indicate a lower level of confidence in the data). Since A. lucii typically displays paired cement glands (Petrochenko 1956), the mean number of paired cement glands in this taxon was assumed to be approximately three (bar shaded grey to indicate approximation).